JP6755475B2 - Indenter transmission type specimen surface observation device, observation method and program for moving image analysis, device control, and characteristic value calculation - Google Patents

Description

The present invention relates to an apparatus and a method for observing the surface of a test piece in a load unloading process of an indentation test, and a program for moving image analysis, apparatus control, and characteristic value calculation.

The indentation test is a test technique that evaluates the deformation characteristics and / and fracture characteristics of a material by pressing a jig called an indenter against the surface of the test piece and using the elasto-plastic stress / strain induced by the load. ..

For example, when the indenter is pressed against the surface of the test piece and the stress generated immediately below the indenter exceeds the elastic limit, plastic deformation is induced in the test piece, and the test piece is observed as an indentation after unloading. The hardness of the test piece is evaluated by measuring the size of this indentation.

Further, since the plastic deformation of the test piece is governed by the number of slip systems determined by the crystal structure of the material, the yield stress of the test piece can be evaluated from the hardness.

In another example, when the brittleness of the test piece dominates the deformation, median cracks occur due to the tensile stress generated immediately below the indenter. The median crack grows to the surface at the time of unloading and forms a median radial crack. When a Vickers type quadrangular pyramid indenter, which will be described later, is used, the median radial crack becomes a cruciform when observed from the surface. The fracture toughness value of the test piece can be evaluated by using the length from the tip to the other end of one side of the cruciform median radial crack observed from the surface.

The conventional indentation test is a test in which the process of applying load stress by pushing an indenter into the test piece and the observation of the state in which the test piece is deformed or / or cracked are performed separately. Therefore, the indentation test is a method for indirectly evaluating the deformation characteristics and / and the fracture characteristics.

On the other hand, there is a microindentation test that can optically measure the projected contact area of an indentation in a state where a load is applied to the surface of the test piece. The microindentation test is a method for directly evaluating the deformation characteristics of a test piece on the spot (for example, Non-Patent Document 1, Non-Patent Document 2, Non-Patent Document 3, Patent Document 1, Patent Document 2, and , Patent Document 3).

Japanese Unexamined Patent Publication No. 2005-195357 Utility Model Registration No. 3182252 Japanese Unexamined Patent Publication No. 2015-175666

T. Miyajima and M. Sakai, Optical indentation microscopy-a new family of instrumented indentation testing, Philosophical Magazine, Vol. 86, pp. 5729-5737 (2006) Norio Hagiri, Motoji Sakai, Tatsuya Miyajima "Development of Microscopic Indenter and Application to Indenter Mechanics", Materials, Vol. 56, No. 6, pp. 510-515 (2007) Mototsugu Sakasai, "Construction of Viscoelastic Indenter Mechanics and Measurement of Rheology in the Micro Region", Journal of the Japanese Society of Rheology, Vol. 39, No. 1-2, pp. 7-15 (2011)

However, in the microindentation test, the refractive index of the material that makes up the indenter is different from the refractive index of the air around the indenter, so refraction occurs at the interface between the indenter and air, causing distortion in the observed image. In some cases, it may be difficult to accurately observe the deformation and / or fracture characteristics that appear on the outer surface of the contact surface by an optical method that allows light to pass through the indenter.

The present invention has been made in view of the actual situation of such a prior art, and an object of the present invention is to provide a technique for observing the surface of a test piece by suppressing the occurrence of refraction at the interface between an indenter and air. ..

In order to solve the above problems, the present invention provides the following observation device and observation method, as well as a program for moving image analysis, device control, and characteristic value calculation.

[1] An observation device for observing the surface of a test piece when a load is applied to the surface of the test piece using a transparent indenter that transmits light of a specific wavelength.
A pressurizing means for applying a load to the test piece and
A load measuring means for measuring the load and
It has an imaging means for imaging the surface of the test body to which a load is applied by the pressurizing means.
The imaging means photographs the test piece through the transparent indenter.
The observation is
(1) Observation of surface shape, twins or dislocations and / and cracks,
(2) Observation to elucidate the mechanism of shape memory alloy,
(3) Observation for screening in alloy development,
(4) Observation to elucidate the stress-induced transformation mechanism,
(5) Observation of fracture and exfoliation of the surface brittle phase,
It is at least one selected from the group consisting of (6) observations for grasping wear characteristics imitating ball-on-disc scratches and (7) observations for evaluating thin film adhesion imitating ball-on-disc scratches.
A liquid is present in the gap between the transparent indenter and the surface of the test piece.
An observation device characterized in that the refractive indexes of the transparent indenter and the liquid are substantially equal when measured at 25 ± 5 ° C. using light having a predetermined wavelength.

[2] When the value of the ratio of the refractive index of the transparent indenter to the refractive index of the liquid is measured at 25 ± 5 ° C. using light of a predetermined wavelength, 1.0: 1. The observation device according to [1], wherein the observation device is 0 ± 0.2.
[3] The observation device according to [1] or [2], further comprising an optical characteristic observation means.
[4] The observation device according to any one of [1] to [3], further comprising a measuring means for measuring the state of the test piece based on the observation result.
[5] The observation device according to [4], wherein the measuring means measures a state of the test body in which the surface shape of the test body is a shape in which the surface of the test body is subducted or raised.
[6] The measuring means is of the twin or dislocation and / and crack.
The observation device according to [4], which measures a position and an orientation.
[7] The measuring means is characterized by measuring the press-fitting depth of the transparent indenter and / or the contact area between the transparent indenter and the sample surface when a load is applied to the surface of the test piece using the transparent indenter. The observation device according to [4].

[8] An observation method for observing the surface of a test piece when a load is applied to the surface of the test piece using a transparent indenter that transmits light of a specific wavelength.
A pressurizing means for applying a load to the test piece and
A load measuring means for measuring the load and
Using the imaging means for imaging the surface of the test body to which the load is applied by the pressurizing means,
A liquid is allowed to exist in the gap between the transparent indenter and the surface of the test piece.
The refractive indexes of the transparent indenter and the liquid are substantially equal when measured at 25 ± 5 ° C. using light of a predetermined wavelength.
The test piece is imaged through the transparent indenter by the imaging means.
(1) Observation of surface shape, twins or dislocations and / and cracks,
(2) Observation to elucidate the mechanism of shape memory alloy,
(3) Observation for screening in alloy development,
(4) Observation to elucidate the stress-induced transformation mechanism,
(5) Observation of fracture and exfoliation of the surface brittle phase,
Observe at least one selected from the group consisting of (6) observations for grasping wear characteristics imitating ball-on-disc scratches and (7) observations for evaluating thin film adhesion imitating ball-on-disc scratches. An observation method characterized by.

[9] When the value of the ratio of the refractive index of the transparent indenter to the refractive index of the liquid is measured at 25 ± 5 ° C. using light of a predetermined wavelength, 1.0: 1. The observation method according to [1], wherein the observation method is 0 ± 0.2.
[10] The observation method according to [8] or [9], further comprising observing the optical characteristics of the test piece using an optical characteristic observing means.
[11] Further, according to any one of [8] to [10], the state of the test body is measured by using a measuring means for measuring the state of the test body based on the observation result. Observation method.
[12] The observation method according to [11], wherein the measuring means measures the state of the test body in which the surface shape of the test body is a shape in which the surface of the test body is subducted or raised.
[13] By the measuring means, the twins or dislocations and / and the cracks
The observation method according to [11], wherein the position and orientation are measured.
[14] The measuring means is used to measure the press-fitting depth of the transparent indenter and / or the contact area between the transparent indenter and the sample surface when a load is applied to the surface of the test piece using the transparent indenter. The observation method according to [11].
[15] A program used in the observation device according to [1].
On the computer
A step of imaging the surface of the test body by the imaging means,
Based on the image of the surface of the test body taken, the state of the test body, which is the shape in which the surface of the test body is subducted or raised according to [5], and / and [6] by the image analysis unit. A moving image analysis program for executing a step of moving image analysis of the position and orientation of the twin or dislocation or / and the crack according to the above, and / and the contact area between the transparent indenter and the sample surface according to [7]. ..
[16] A program used in the observation device of [1].
On the computer
Steps to accept various test conditions entered by the user,
Steps to drive the precision positioning device based on the various test conditions received,
A device control program for executing a step of controlling a load applied to the surface of the test piece by the pressurizing means by using the transparent indenter through the driving of the precision positioning means.
[17] A program used in the observation device of [1].
On the computer
A step of imaging the surface of the test body by the imaging means,
Based on the image of the surface of the test piece taken, the value measured by the observation device for the state of the test piece according to [5] and the twin crystal or dislocation or / and crack described in [6]. A characteristic value calculation program for executing a step of calculating the characteristic value of the test piece from the position and orientation, the press-fitting depth of the transparent indenter according to [7], and / or the contact area between the transparent indenter and the sample surface.

As described above, according to the present invention, since the refraction at the interface between the indenter and the air can be controlled, contact is performed by an optical method of transmitting light through the indenter in a state where a load is generated in the microindentation test. It is possible to observe and / and measure the deformation property and / and the fracture property appearing on the outer surface of the surface clearly and in detail.

It is a block diagram explaining an example of the basic structure of the measuring apparatus provided with the observation apparatus which concerns on one Embodiment of this invention. It is a figure explaining an example of the structure of the indentation tester in the measuring apparatus provided with the observation apparatus which concerns on one Embodiment of this invention. It is a side view explaining the focusing angle of the objective lens of the optical microscope for observing the contact between a transparent indenter and the surface of a specimen. It is explanatory drawing of the indenter whose tip shape of an indenter is a triangular pyramid. It is explanatory drawing of the indenter whose tip shape of an indenter is a quadrangular pyramid. Bakabitchi (Berkovich) type triangular pyramid indenter (surface inclination angle beta: 24.97 degrees) to a view for explaining the refraction at the interface between the refractive index adjusting liquid is a refractive index n ₂ and indenter a refractive index n ₁ as an example is there. It is a figure explaining the influence of the refraction at the interface between an indenter and a refractive index adjusting liquid on a focal position by taking a spherical indenter as an example. This is the result of calculating the deviation of the focal position caused by the refraction at the interface between the indenter and the refractive index adjusting liquid using a spherical indenter (radius: 500 microns) as an example. This is the result of calculating the focal distortion of the observed image caused by the refraction at the interface between the indenter and the refractive index adjusting liquid using a spherical indenter (radius: 500 microns) as an example. It is a figure explaining the two-dimensional distortion of the observation image caused by the refraction at the interface between an indenter and a refractive index adjusting liquid, taking a spherical indenter (radius: 500 microns) as an example. This is the result of calculating the two-dimensional distortion of the observed image when the combination of the indenter and the refractive index adjusting liquid is changed using a spherical indenter (radius: 500 microns) as an example. Taking a spherical indenter (radius: 500 microns) as an example, the calculation results and experimental results show the two-dimensional distortion that the refraction at the interface between the indenter and the refractive index adjusting liquid exerts on the observed image after pushing 10 microns. Taking a spherical indenter (radius: 500 microns) as an example, the calculation results and experimental results regarding the deviation between the position of the observation image caused by refraction at the interface between the indenter and the refractive index adjusting liquid and the true position on the surface of the test piece. is there This is an image taken in a state where the triangular pyramid indenter (barkavic type indenter made of sapphire) and the microscale (10 micron pitch) in the embodiment of the present invention are in contact with each other, and the refractive index adjusting liquid is placed in the gap between the indenter and the microscale. It is the figure which compared the case (A) which does not exist and the case (B) which exists. It is an image taken in a state where a spherical indenter (made of sapphire or made of quartz glass) and a metal test piece (single crystal of sterling silver) in the embodiment of the present invention are in contact with each other. Silicone oil was selected as the contact liquid (refractive index adjusting liquid) in the case of sapphire indenter, and kerosene was selected in the case of quartz glass indenter. This is an image taken in a state where a sapphire indenter (spherical indenter) and a metal test piece (single crystal of pure magnesium and a single crystal of magnesium alloy) in the embodiment of the present invention are in contact with each other. The dimensions of the long axis and single axis of the contact surface (ellipse) between the sapphire indenter (spherical indenter) and the metal test piece (single crystal of pure magnesium and single crystal of magnesium alloy) in the examples of the present invention are set with respect to the load. It is a figure plotted. It is a stress-strain curve of the loading process in the contact between the sapphire indenter (spherical indenter) and the metal test piece (single crystal of pure magnesium and single crystal of magnesium alloy) in the embodiment of the present invention. It is a figure which plotted the scale of plastic deformation at the contact between a sapphire indenter (spherical indenter) and a metal test piece (a single crystal of pure magnesium and a single crystal of a magnesium alloy) in the Example of this invention. Image of unloading process and FE-SEM / EBSD analysis after test in contact between sapphire indenter (spherical indenter) and metal test piece (single crystal of pure magnesium and single crystal of magnesium alloy) in the examples of the present invention. It is an image.

Hereinafter, embodiments of the present invention will be described.

FIG. 1 is a block diagram illustrating an example of a basic configuration of a measuring device for performing an indentation test (hereinafter, also simply referred to as a measuring device) provided with an observation device according to an embodiment of the present invention.

The measuring device that performs this indentation test is a microindentation tester 1 that measures various mechanical characteristics of the test piece 5 by bringing a transparent indenter 4 (hereinafter, also referred to as an indenter 4) into contact with the surface of the test piece 5. It is composed of a control device 2 and an information processing device (computer) 6.

The measurement control device 2 adjusts the distance between the video camera (camera) 7 (imaging means) that records the contact of the transparent indenter 4 with the surface of the test piece 5 as an image, and the surface of the transparent indenter 4 and the test body 5. It is composed of a precision positioning device 8 (pressurizing means) for making contact with each other and a load measuring device 9 (load measuring means) for measuring the load generated by the contact between the transparent indenter 4 and the test body 5. Although not shown, a separate light source is required for observation with the video camera (camera) 7. In the case of a general optical microscope, white light in the visible light region is used, and in the case of a laser microscope, a monochromatic light beam of a laser in the wavelength band from near ultraviolet (about 300 nm) to infrared (about 10 microns) is usually used. Be done. Hereinafter, the wavelength of 632.8 nm may be referred to as a predetermined light of a light source in the present invention. In addition, white light may be used when observing polarized light of a metal or the like at the same time. Here, when the wavelength is short, the resolution is high and a fine structure can be observed, and when the wavelength is long, the whole can be observed.

The information processing device 6 is a computer (electronic computer), and is an input / output I / F (Interface) 10, a CPU (Central Processing Unit) 12, a condition setting unit 13, a characteristic value calculation unit 14, an image analysis unit 11, and a storage. It is composed of a device 15. Each element of the information processing apparatus 6 is connected by a bus.

The moving image analysis program used in the image analysis unit 11 of the information processing device 6 is stored in the storage device 15, and through the condition setting unit 13, selection of an image analysis method, Roy (image analysis area), and parameters (various types). The user is prompted to input through the input / output I / F10 so as to set (analysis conditions, etc.), and further, it is expanded on a main storage device such as a computer memory and executed.

The device control program used in the device control unit of the information processing device 6 is stored in the storage device 15, and various test conditions (maximum load load value, test time, etc.) are set through the condition setting unit 13. It prompts the user for input through the input / output I / F10, and is further expanded on a main storage device such as a computer memory for execution.

The characteristic value calculation program used by the characteristic value calculation unit 14 of the information processing device 6 is stored in the storage device 15, and includes the contact area analyzed by the image analysis unit 11 and the load value measured by the load measurement device 9. Calculate various mechanical properties (stress-strain curve, Meyer hardness, Young's modulus, yield value, etc.) from. In addition, the surface deformation parameter γ, which is a numerical value of subduction or swelling, is calculated from the surface profile obtained by scanning the surface of the test piece. Alternatively, the positions, dimensions, orientations, etc. of twins (dislocations), stress-induced transformation phases, cracks, fractures, peelings, wear, etc. recognized by the image analysis unit 11 are automatically calculated. In addition, the indenter indentation depth and / and the relationship between the contact area and the load are plotted.

The observation device of the present embodiment includes a microscopic indentation tester 1, a measurement control device 2, and an information processing device 6. Further, the observation device of the present embodiment has a configuration including a measurement control device 2 and an information processing device 6 as measuring means for measuring the state of the test body 5 based on the observation result of the test body 5, and is inden as a whole. It constitutes a measuring device that performs a tension test.

FIG. 2 is an example of the functional configuration of the microindentation tester 1 in the measuring device provided with the observation device according to the embodiment of the present invention.

The positioning device 8 makes contact between the surface of the test piece 5 and the tip of the transparent indenter 4. The load generated by the contact is measured by the load measuring device 9.

Further, since the transparent indenter 4 is fixed to the transparent indenter holding plate 19, the state of the surface of the test piece 5 is observed from the outside of the testing machine frame 18 in the entire process of the indentation test in which the test piece 5 is loaded. it can. Various mechanical phenomena caused by the load applied to the test body 5 are optically magnified by the microscope 3 (optical property observing means) provided with the objective lens 17, and the video camera attached to the microscope 3 ( The image can be taken by the camera) 7. In order to realize this, the optical axis of the microscope 3 is arranged so as to coincide with the optical axis connecting the transparent indenter 4 and the contact portion.

The refractive index adjusting liquid (contact liquid) 20 is selected substantially equal to the refractive index of the transparent indenter 4 appropriately selected according to the characteristics of the test body 5, and is inserted into the gap between the test body 5 and the transparent indenter 4. ..

The captured image captured by the video camera 7 is written in the recording device 15 as a mechanical phenomenon associated with the elapsed test time. Further, this captured image can be transferred to the image analysis unit 11 of the information processing apparatus 6 and digitized by a moving image analysis program.

FIG. 3 is a diagram for explaining the state of contact between the indenter and the surface of the test piece according to the embodiment of the present invention. Here, as an example, the tip radius of curvature of the indenter is conical with a micrometer order or less, and the surface is inclined. An acute-angled indenter having an angle of β (FIG. 3 (A)) and a spherical indenter having a spherical tip (FIG. 3 (B)) are drawn.

The acute-angled indenter is an indenter having a shape with one protrusion at the tip and the angle formed by the surface of the test piece and the indenter surface can be expressed by one surface inclination angle β. For example, a triangular pyramid, a quadrangular pyramid, and an indenter. It is a cone. Vickers indenter (plane inclination angle β = 22.0 degrees) and Barkavic indenter (plane inclination angle β = 24.97 degrees, or 24.73 degrees), which are widely used mainly for the purpose of measuring the hardness of metals and ceramics. Degree) is an acute angle indenter. Further, the triangular pyramid indenter having a ridge spacing of 90.0 degrees and the pyramid indenter having a facing angle of 90.0 degrees are acute angle indenters.

On the other hand, the spherical indenter has a spherical surface at the tip of the indenter, and the surface thereof has a surface that can be represented by a constant diameter (radius r, diameter D). The Brinell indenter (diameter D = 1, 2.5, 5, 10 mm) and the Rockwell indenter (tip radius of curvature r = 200 microns), which are widely used mainly for the purpose of measuring the hardness of metal, are spherical indenters. Is.

In the microindentation tester 1, the state of contact between the indenter and the test piece is observed by using a video camera (camera) coupled to an optical microscope and allowing the indenter to transmit light. Therefore, the indenter has a characteristic of translucency. It is necessary to have properties, and suitable materials include diamond, sapphire, glass and the like. The indenter used in the present invention is a transparent indenter. For light having a wavelength of 589.3 nm, the refractive index _{n i} of the material constituting the indenter, diamond 2.420, sapphire 1.768, quartz glass is 1.456, optical glass (BK7) is at 1.517 is there.

Air is a medium existing around an indenter and has a refractive index of 1.000. A general reagent or contact liquid (refractive index adjusting liquid) is also a medium around the indenter, and its refractive index _nr can be selected from various types. It relates the refractive index ratio n _{r /} n _i In the present invention, various indenter - and to a discussion of the combination of the refractive index adjusting liquid.

For example, when selecting a kerosene (refractive index _n r = 1.43) as a refractive index adjusting liquid, the refractive index of the quartz glass _n i (= 1.456) and nearly the refractive index ratio _n r / _{n i} is 0. It becomes 98. Further, the optical glass (BK7, refractive index _n i = 1.517) refractive index ratio _n r / _{n i} in combination with becomes 0.94. Further, the refractive index ratio is in combination with sapphire (refractive index _{n i = 1.768) n r /} n i becomes 0.80.

On the other hand, when selecting a silicone oil (refractive index _n r = 1.51) as a refractive index adjusting liquid, close to the value (the refractive index _n i = 1.517) of the optical glass (BK7), the refractive index ratio _n r / n _i will be 0.995. The refractive index ratio is in combination with sapphire (refractive index _{n i = 1.768) n r /} n i becomes 0.85. Further, the refractive index ratio is in combination with quartz glass (refractive index _{n i = 1.456) n r /} n i becomes 1.037.

Further, a refractive index adjusting solution having a refractive index adjusted from 1.48 to 1.78 in increments of 0.01 is commercially available. Bringing the refractive index ratio n _{r /} n _i to 1, suitable indenter - it is possible to select a set of refractive index adjusting liquid. The value of the ratio of the refractive index of the transparent indenter to the refractive index of the contact liquid (refractive index adjusting liquid) is preferably 1.0: 1.0 ± 0.2.

FIG. 4 is a diagram illustrating triangular pyramids having different surface inclination angles for an indenter whose tip shape is a triangular pyramid. In the tip shape of the Berkovich type indenter widely used in instrumentation indentation tests, the tip surface angle α is 65.03 degrees, the tip edge angle ψ is 76.89 degrees, and the surface inclination angle β is 24.97. The degree and the ridge interval 2θ are 115.02 degrees. In a corner cube type triangular pyramid indenter, the tip surface angle α is 35.26 degrees, the tip edge angle ψ is 54.74 degrees, the surface inclination angle β is 54.73 degrees, and the edge spacing 2θ is 90 degrees. Is.

FIG. 5 is a diagram illustrating quadrangular pyramids having different surface inclination angles for an indenter having a quadrangular pyramid tip shape. In the tip shape of the Vickers type indenter widely used in the hardness test of general metals and ceramics, the tip surface angle α is 68.00 degrees, the tip edge angle ψ is 74.00 degrees, and the surface inclination angle β. Is 22.00 degrees, and the ridge spacing 2θ is 85.67 degrees. Further, in a quadrangular pyramid indenter having a right-angled prism structure in which the facing angle of the indenter tip is 90.0 degrees, the tip surface angle α is 45.00 degrees, the tip ridge angle ψ is 54.74 degrees, and the surface inclination angle β is 45.00. The degree and the ridge interval 2θ are 70.53 degrees.

The space before being incident on an optical system such as a magnifying lens is an object space, and the space where an image can be formed after passing through all the optical systems is an image space. According to this definition, in the case of the microscopic indentation tester 1, since the transparent indenter 4 is also a part of the optical system, the total optical system is a combination of the magnifying optical system and the indenter optical system constituting the microscope. The object space of the microscopic indentation tester 1 is from the tip to the surface of the test piece.

The objective lens 17 of the microscope has a focusing characteristic, and has a numerical aperture NA (Numerical Aperture) as a numerical value that determines the resolution of the objective lens 17. The focusing angle θ ₁ of the objective lens 17 is an angle formed by the optical axis, and can be expressed by the following equation, where n is the refractive index of the medium (air) in the object space and NA is the numerical aperture of the lens.

Further, the substance 1 and the substance 2 are in contact with each other, and their refractive indexes are n ₁ and n ₂ , respectively, and the incident angle θ ₁ and the exit angle θ ₂ when light passes from the substance 1 to the substance 2 at the interface thereof. The relationship with can be described by the following equation, which is well known as "Snell's law" (Fig. 6).

Further, how much the light (incident angle θ ₁ ) incident on the interface of the known refractive index (n ₁ and n ₂ ) is refracted, that is, the emission angle θ ₂ can be known by modifying Eq. (2). Can be done.

As shown in FIGS. 3 (A) and 3 (B), when the medium 1 is air (refractive index n ₁ = 1.000) and the medium 2 is diamond (refractive index n ₂ = 2.4195), diamond. The maximum emission angle θ ₂ at which light incident on the surface at an incident angle θ ₁ (= 14.48 degrees) is emitted to the diamond is calculated as 5.93 degrees from Eq. (3).

This example is for a focusing angle θ ₁ (14.48 degrees), which is the maximum focusing angle of a commercially available objective lens (LMPlanFL, 10X, NA = 0.25, manufactured by Olympus), and is inside a diamond indenter. The maximum refraction angle θ _{2 to} is 5.93 degrees. That is, the light emitted from the diamond indenter at an angle θ ₂ within 5.93 degrees reaches the objective lens (LMPlanFL, 10X, manufactured by Olympus) and is observed as an image of an optical microscope.

When the medium 1 is air (refractive index n ₁ = 1.000) and the medium 2 is sapphire (refractive index n ₂ = 1.768), the angle of incidence with respect to the sapphire surface is θ ₁ (= 14. The maximum emission angle θ ₂ at which the light incident in 48) is emitted to the sapphire is calculated to be 8.13 degrees from the equation (3).

This example is for a focusing angle θ ₁ (14.48 degrees), which is the maximum focusing angle of a commercially available objective lens (LMPlanFL, 10X, manufactured by Olympus), and the maximum refraction angle θ ₂ inside the sapphire indenter. Is 8.13 degrees. That is, the light emitted from the sapphire indenter at an angle θ ₂ within 8.13 degrees reaches the objective lens (LMPlanFL, 10X, manufactured by Olympus) and is observed as an image of an optical microscope.

There is a maximum value for the angle of incidence at which refraction occurs, and the angle of incidence is the critical angle (θ _m ). Total internal reflection occurs above the critical angle. Under the condition that the refractive index n ₁ > the refractive index n ₂ , the emission angle θ ₂ = 90 degrees is critical. Therefore, when the equation (2) is modified, the critical angle θ _m is the following equation.

When the medium 1 is diamond (refractive index n ₂ = 2.420) and the medium 2 is air (refractive index n ₁ = 1.000), the critical angle θ _m at which the light transmitted through the diamond is not emitted into the air. Is calculated as 24.41 degrees from Eq. (4). Similarly, when the medium 1 is sapphire (refractive index n ₂ = 1.768), the critical angle θ _m is calculated to be 34.45 degrees from the equation (4).

At an angle of the critical angle θ _m or more, light cannot be emitted to the medium 2 and returns to the medium 1 again. This is total reflection. That is, when the light transmitted through the diamond is incident at an angle larger than 24.41 degrees from the perpendicular of the diamond / air interface, the light is totally reflected inside the diamond without being emitted into the air. Similarly, when the light transmitted through the sapphire is incident at an angle larger than 34.45 degrees from the perpendicular of the sapphire / air interface, the light is totally reflected inside the sapphire without being emitted into the air.

The shape of the indenter tip most frequently used in the indentation test in the micro / nano region is a triangular pyramidal-shaped Berkavic indenter (plane inclination angle β (= 24.97 degrees)). Therefore, next, let us consider the ray path for the Berkavic indenter whose material is diamond (refractive index n ₂ = 2.420) and sapphire (refractive index n ₂ = 1.768).

FIG. 6 shows the relationship between the inclined surface of the Berkavic indenter and the light beam according to the embodiment of the present invention, and is drawn so that the inclined surface of the indenter is perpendicular to the paper surface. In addition to the surface inclination angle β (= 24.97 degrees) of the Berkavic indenter, the tip surface angle α (= 65.03 degrees) and the tip ridge angle ψ (= 76.89 degrees) are shown in the figure. ..

The gap between the indenter and the surface of the test piece is filled with air (refractive index n ₂ = 1.000) or a medium (refractive index adjusting liquid, refractive index n ₂ ).

First, consider the case where the optical axis of the tip of the indenter (broken line in FIG. 6) is perpendicular to the surface of the test piece and parallel to the optical axis of the optical microscope.

Since the angle θ ₁ is the same angle as the surface inclination angle β, it is the same value as the surface inclination angle β. That is, the angle θ ₁ is 24.97 degrees.

When the indenter is made of diamond and the surrounding medium is air, the critical angle θ _m of the diamond / air interface is 24.41 degrees from Eq. (4). The incident angle of the light ray is larger than the critical angle θ _m when it is 24.97 degrees, which is equal to the angle θ ₁ formed by the indenter's surface. Therefore, the light emitted vertically through the objective lens of the optical microscope is totally reflected by the inclined surface of the indenter.

When a confocal laser scanning microscope is used as the optical microscope, the focusing angle θ ₁ and the refraction angle θ ₂ are both 0 degrees. However, as described in paragraph 0051, the light rays in the indenter may not be perpendicular to the top surface of the specimen when the focusing angle of the objective lens is taken into consideration. Taking the focusing angle θ ₁ (14.48 degrees), which is the maximum focusing angle of a commercially available objective lens (LMPlanFL, 10X, NA = 0.25, manufactured by Olympus), as an example, the maximum refraction inside the diamond indenter The angle θ ₂ is 5.93 degrees (Fig. 3). The maximum refraction angle θ ₂ is the case of an image observed at the outermost peripheral portion of the objective lens, and the refraction angle θ ₂ is 0 degrees when observing at the center of the objective lens.

For a ray with a maximum refraction angle θ ₂ of 5.93 degrees, the angle of incidence of the ray on the perpendicular at the diamond / air interface is only 5.93 degrees greater than the angle θ ₁ (24.97 degrees) created by the indenter's surface. It is a small 19.04 degrees. This angle is smaller than the critical angle θ _m, which is 24.41 degrees. Therefore, it is emitted to the air (outside the indenter) without total internal reflection on the inclined surface of the indenter. The emission angle is calculated to be 7.75 degrees using Eq. (3). That is, the light incident on the inclined surface of the diamond indenter from the diamond side at an incident angle θ ₁ (= 19.04 degrees) is emitted to the air at an exit angle θ ₂ (= 7.75 degrees).

As another example, if the indenter is made of sapphire and the surrounding medium is air, the critical angle θ _m of sapphire / air is 34.45 degrees. Since the angle θ ₁ (= 24.97 degrees) is smaller than the critical angle θ _m , the light emitted from the optical microscope parallel to the optical axis of the indenter is not totally reflected by the inclined surface of the indenter and is outside the indenter ( It emits to the air).

The emission angle is calculated to be 13.81 degrees using Eq. (3). That is, the light incident on the inclined surface of the sapphire indenter from the sapphire side at an incident angle θ ₁ (= 24.97) is emitted to the air at an exit angle θ ₂ (= 13.81 degrees).

Further, when the indenter is made of sapphire and the surrounding medium is a refractive index adjusting liquid in which the refractive index n ₂ is adjusted to 1.77, the critical angle θ _m of sapphire / air is 90 degrees. Since the angle θ ₁ (= 24.97 degrees) is smaller than the critical angle θ _m , the light emitted from the optical microscope parallel to the optical axis of the indenter is not totally reflected by the inclined surface of the indenter and is air (indenter). Exit to the outside). The emission angle is calculated to be 25.00 degrees using the equation (3). That is, light incident on the interface between the inclined surface of the sapphire indenter and the contact liquid (refractive index n = 1.77) at an incident angle θ ₁ (= 24.97) from the sapphire side is emitted to the contact liquid. It emits light at θ ₂ (= 25.00 degrees).

As described in paragraph 0051, the light rays in the indenter may not be perpendicular to the specimen when considering the focusing angle of the objective lens. Taking the focusing angle θ ₁ (14.48 degrees), which is the maximum focusing angle of a commercially available objective lens (LMPlanFL, 10X, manufactured by Olympus), as an example, the maximum refraction angle θ ₂ inside the sapphire indenter is 8. It is .13 degrees. The maximum refraction angle θ ₂ is the case of an image observed at the outermost peripheral portion of the objective lens, and the refraction angle θ ₂ is 0 degrees when observing at the center of the objective lens.

For a ray with a maximum refraction angle θ ₂ of 8.13 degrees, the angle of incidence of the ray on the perpendicular at the sapphire / air interface is only 8.13 degrees greater than the angle θ ₁ (24.97 degrees) created by the indenter surface. It is a small 16.84 degrees. This angle is smaller than the critical angle θ _m, which is 24.41 degrees. Therefore, it is emitted to the air (outside the indenter) without total internal reflection on the inclined surface of the indenter. The emission angle is calculated to be 9.43 degrees using Eq. (3). That is, the light incident on the inclined surface of the sapphire indenter from the sapphire side at an incident angle θ ₁ (= 16.84 degrees) is emitted to the air at an exit angle θ ₂ (= 9.43 degrees).

The Brinell indentation test is heavily used in the hardness test using a metal as a test piece. The indenter used in the Brinell indentation test is a spherical indenter. Therefore, next, a hemispherical spherical indenter (radius r = 500 microns) will be considered.

The characteristic of the shape of the spherical indenter is that the incident angle θ ₁ with respect to the interface between the indenter and the refractive index adjusting liquid increases as the epi-illumination position of the optical path moves away from the contact center between the indenter and the surface of the specimen. When the incident angle θ ₁ exceeds the critical angle θ _m , total reflection occurs and an observation image cannot be obtained. Therefore, with a hemispherical spherical indenter, an invisible region where an observed image cannot be obtained occurs in a region near the outer edge. By approaching the refractive index ratio n _r / _ni to 1, the critical angle θ _m approaches 90 degrees, and the invisible region can be reduced. When the refractive index ratio is n _r / _ni > 1, total reflection does not occur.

The case where the refractive index ratio n _r / _ni is variously changed with respect to a hemispherical spherical indenter will be examined in detail three-dimensionally by simulation of the optical path.

Regarding the combination of indenter and refractive index adjuster, sapphire-air (comb.1), quartz glass-air (comb.2), sapphire-silicone oil (comb.3) and quartz glass-kerosin (comb.4), Using a sapphire-sapphire-dedicated refractive index adjusting solution (comb.5, n _r = 1.77) as an example, both simulation and experiment will be examined.

The light incident on the test body has a component having an angle in addition to the vertical fall light with respect to the test body, and the magnitude of the angle can be obtained from the numerical aperture NA of the objective lens. In this simulation, 0.16 is used as the numerical aperture NA value. Since a microscope using a monochromatic laser beam has no chromatic aberration, if the space between the lens and the smooth surface of the specimen is occupied by a medium having a uniform refractive index, the focal position is set to the surface of the specimen in the entire observation region. It is possible to match. However, in this device, the laser light passes through three types of media having different refractive indexes: atmosphere, indenter, and refractive index adjusting liquid.

Since light is refracted each time it passes through the interface between two kinds of substances having different refractive indexes, the focal position does not match the surface of the specimen. This mismatch, the indenter - calculated using the refractive index of kerosene _{(comb.4, n r / n i} = 0.98) - quartz glass as a set of refractive index adjusting liquid.

As shown in FIG. 7, consider Ray1 and Ray2 corresponding to the same position in the laser photodetector in the confocal optical system. Ray 1 is light that passes through the center of the objective lens, and Ray 2 is light that passes through the end of the objective lens on the focal position side. Although there is epi-illumination other than Ray1 and Ray2, the calculation is performed using the combination of Ray1 and Ray2 that maximizes the difference between the surface of the test piece and the focal position.

Here, the distance between the surface of the test piece and the parallel direction is considered. Let w be the distance between the focal position determined as the intersection of Ray1 and Ray2 and the contact center point of the indenter-test piece. The focal position f at each w is shown in FIG. The focal position coincides with the surface of the specimen at f = -500 microns.

It can be seen that as w increases, the distance between the focal position f and the surface position of the test piece (f = −500 micron) becomes divergent. Further, when the focal position f is separated from −500 microns, the observation image is formed by the light of different optical paths reflected from the surface of the test piece.

Let dw be the difference in image formation position on the test piece surface with respect to each point of w. The difference dw is shown in FIG. It can be seen that dw also increases as w increases.

On the other hand, the resolution δ in the optical microscope is expressed by the following equation (Rayleigh's equation).

By substituting the wavelength λ (= 632.8 nm) of the He-Ne laser beam and the numerical aperture NA (= 0.16) of the objective lens into the equation (5) as typical values, the optical resolution δ = 1 Obtain .76 microns.

From FIG. 9, it can be seen that the distance w that produces the difference dw (= 1.76 microns) of the imaging positions corresponding to the optical resolution δ = 1.76 microns is 399 microns.

That is, the dw in the range where the distance from the indenter center is 399 microns or less in radius is smaller than the resolution of the confocal laser scanning microscope and does not hinder the observation. When the indentation load is sufficiently small and the observation radius is 396 microns or less, a clear image can be obtained in the entire observation region.

Further, when the combination of the indenter and the refractive index adjusting liquid is changed in various ways, the calculation is performed based on the optical model shown below in order to predict how the image obtained for each combination will change. Here, λ = 632.8 nm (He-Ne laser) is used as the wavelength of light.

As shown in FIG. 10, considering the vertical epi-illumination Ray3, the distance from the indenter center to the observed position is defined as x, and the position formed by the laser photodetector is defined as a. The results of calculating the relationship between x and a under each condition are shown in FIGS. 11 and 12.

If the space between the lens and the surface of the test piece is occupied by a medium having a uniform refractive index, then x = w. The distance w here is as shown in FIG. 7, and when n _r / _ni is sufficiently close to 1, it is approximated as x = w.

11 and is indicated dotted line in FIG. 12 condition equation of x = a is satisfied, that is, the refractive index ratio of the indenter and the refractive index adjusting liquid n _{r /} n _i is 1, refraction of light occurs It means no state. It can be seen that the closer the refractive index ratio n _r / _ni is to 1, the closer the distance x is to the imaging position a, that is, the closer to x = a shown by the dotted line.

Further, when the imaging position a exceeds a certain value (for example, in comb.1, a = 279 microns), the distance x corresponding to the imaging position a does not exist. This is due to the total reflection of light described above. Since the indenter is a hemispherical spherical surface, the incident angle θ ₁ becomes larger as the distance from the center point of the osculating circle between the indenter and the test piece increases, and total reflection occurs at a position where the imaging position a is larger than a certain value.

The combined refractive index ratio n _{r /} n _i is less than 1, the refractive index ratio n _{r /} n _i is close to the critical angle theta ₀ is 90 ° closer to 1, the total reflection occurs condition spherical are met It becomes difficult. Therefore, by using the refractive index adjusting liquid, it is possible to reduce the non-imaging region due to total reflection, and the observable region becomes large.

In the combination of each refractive index ratio n _{r /} n _i, the range of observable specimen surface can be known from the maximum value of the distance x. As an example, the maximum values of the distance x in comb.1 and comb.4 are 206 microns and 441 microns, respectively.

In each combination of the refractive index ratio n _{r /} n _i, there is a region where there are two imaging position a with respect to one distance x. This means that the surface of the specimen at a certain position is imaged in two places. However, as shown in FIG. 8, as the observation position approaches the edge of the indenter, the distance between the focal position f and the surface of the test piece (f = -500 microns) increases, so that a clear observation image is obtained at the edge of the indenter. I can't get it.

Next, the two-dimensional distortion of the observed image, that is, the deviation between the true position on the surface of the test piece and the position of the observed image is verified from both calculation and experiment.

As shown in FIG. 13, in order to visualize the two-dimensional distortion of the observed image, consider marking points at 25 micron intervals on the surface of the specimen.

Indenter - quartz glass as a set of refractive index adjusting liquid - kerosene _{(comb.4, n r / n i} = 0.98) the refractive index with the perpendicular incident light to the test surface (wavelength lambda = 632.8 nm (He-Ne laser)) is used for observation.

X and a in FIG. 13 are those defined in FIG. 10, and are approximated to x = w under this condition in which the refractive index ratio n _r / _ni is close to 1.

As an example of the observation image obtained by the calculation, a case where the pushing depth h is 0 micron (no load) and a case where the pushing depth h is 10 microns are shown. The pushing depth h here is defined in FIG. The closer to the edge of the indenter, the greater the distortion of the image, that is, the difference between the actual position x and the imaging position a. In addition, no marking points are observed near the edge of the indenter due to total internal reflection of light. These calculation results are in agreement with FIG. 12 of the calculation results obtained under the same assumption.

The above calculation results will be verified by experiments using a microscopic indentation device. Pure Ag was selected as the test body. A nanoindenter (manufactured by HYSITRON, TriboIndenter, TI950) was used as marking points on the surface of the indentation test piece of Pure Ag, and microindentations of 40 points in length × 40 points in width, totaling 1600 points, were made at 25 micron intervals.

Indenter - as a combination of refractive index adjusting liquid, silica glass - Select kerosene (Comb.4, the refractive index ratio _{n r / n i = 0.98)} , were microscopic indentation test room temperature, in air. In the experiment, the displacement rate was set to 1 micron per second.

The experimental results are shown in FIG. The white dashed line shown in the figure is drawn as a mark indicating the interval of 50 microns. The observed marking points are located outside the white dashed line of the mark, and the experimental results and the calculated results are in good agreement.

According to the present invention, the surface of a test piece under load can be observed clearly and in detail by a method of transmitting light through a transparent indenter and measured on the spot. Therefore, the load stress value can be calculated from the measured values of the load and the contact area, and the following various tests can be realized.
(1) Observation of surface shape, twins or dislocations and / and cracks,
(2) Observation to elucidate the mechanism of shape memory alloy,
(3) Observation for screening in alloy development,
(4) Observation to elucidate the stress-induced transformation mechanism,
(5) Observation of fracture and exfoliation of the surface brittle phase,
(6) Observation to grasp the wear characteristics imitating a ball-on-disc scratch,
(7) Observation for evaluation of thin film adhesion imitating ball-on-disk scratch, and (8) Observation in combination with optical characteristic observation method

As indenter, triangular pyramid indenter (sapphire, Bakabitchi type, refractive index n _{i =} 1.768) select, as the liquid filling the gap between the indenter and the test surface, a commercially available contact liquid (refractive index adjusting liquid) ( An example of an experiment using a refractive index n _r = 1.77, manufactured by Shimadzu Device Co., Ltd., product number: nd1.77) is shown. This combination (comb.5) is a refractive index ratio _n r _{/ n} i = 1.00.

FIG. 14 is an image of a scale bar imaged by epi-illumination of an optical microscope with the tip of a sapphire indenter in contact with the surface of a microscale (10 micron pitch, metal, reflective). FIG. 14A shows a case where air is present in the gap between the sapphire indenter and the microscale, and FIG. 14B shows a refractive index adjusting liquid (refractive index _nr =) in the gap between the sapphire indenter and the microscale. This is the case when 1.77) exists.

In the case of sapphire / air shown in FIG. 14 (A), since it is emitted from the inclined surface of the indenter at an emission angle θ ₂ of 13.81 degrees, it is 11.16 degrees (= 24.97-13. Since the refraction of light (prism effect) of only 81) occurs, the image is distorted.

On the other hand, if the sapphire shown in FIG. _{14 (B) (n i =} 1.768) / refractive index adjusting liquid _(n r = 1.77), refraction at the interface -0.03 ° (= 24.97- 25.00). This was successful, and the distortion of the image was extremely small, indicating that the appearance of the microscale surface (10 micron pitch bar) of the test piece could be observed clearly and in detail.

An experimental example using a hemispherical spherical indenter (radius r = 500 microns) as an indenter is shown. The conditions of the microindentation test were normal temperature and air, the displacement rate was 1 micron per second, and the maximum pushing load was 4.9 N or 9.8 N.

A microindentation test was carried out using Pure Ag (pure silver) having an average crystal grain size on the order of microns as a test piece. Pure Ag is easy to mirror-polish and has good oxidation resistance, so that a good surface condition of the test piece can be maintained during the test. In addition, Pure Ag has an FCC structure having a relatively low hardness and good symmetry, and is isotropically plastically deformed, so that it is suitable as a model material for evaluation. The cast material of Pure Ag was mechanically polished with emery paper and an alumina abrasive (particle size 0.1 micron) to prepare a test piece.

Indenter - as a combination of refractive index adjusting liquid, sapphire - air (Comb.1, the refractive index ratio _{n r / n i = 0.56)} , silica glass - air (Comb.2, the refractive index ratio _n r / _{n i} = 0.68), sapphire - silicone oil (Comb.3, the refractive index ratio _{n r / n i = 0.85)} , and quartz glass - kerosene (Comb.4, the refractive index ratio _n r / _{n i} = 0. 98) was selected.

FIG. 15 is an in-situ observation image by the microindentation device under each condition. As can be seen from the observation image, this method enables in-situ observation of the surface of the test piece around the contact surface at the same time as the process of increasing the contact area between the indenter and the test piece as the pushing load increases.

From situ observation image shown in FIG. 15, the refractive index ratio _{n r / n i = 0.56 (} comb.1), but can only approximately situ observation of increased process of indenter contact area, more condition refractive index ratio increases _{(n r / n i = 0.68} (comb.2)) At the same time be in situ observation of the condition of the test piece surface surrounding the indenter contact circle with increasing process of the indenter contact area becomes possible, it gets closer to the refractive index ratio n _{r /} n _i further 1, regions of the observable test surface is expanding.

These results indicate that an appropriate image can be obtained by selecting an indenter-refractive index adjusting liquid pair suitable for the region where the surface of the test piece is observed.

As a third embodiment, showing the case of using as a spherical spherical side hemisphere indenter (sapphire, a refractive index n _{i =} 1.768). As a liquid that fills the gap between the indenter and the surface of the test piece, a commercially available silicone oil (refractive index _rn = 1.51) was used as the refractive index adjusting liquid. In this example, the refractive index ratio _n r / _{n i} becomes 0.85.

A single crystal of magnesium (Pure Mg) and a single crystal of magnesium alloy (Mg-1.3at.% Y, Mg-2.3at.% Y) are used as test specimens, and the maximum load is up to 9.8N. Was applied in a direction parallel to [1-210] and recorded with a laser microscope.

FIG. 16 shows Pure Mg, Mg-1.3 at. % Y and Mg-2.3 at. It is an in-situ observation image recorded at no load 0.0N and load load 9.8N in the microindentation test using each single crystal of% Y, and the elliptical indentation shown by the dotted line is in the indentation process. In-situ was observed.

In general, the projected indentation shape by Brinell indentation is circular, reflecting the indenter shape, but in microindentation using Pure Mg single crystal, in-situ observation of the indentation process confirmed the formation of elliptical indentation. The major axis and the minor axis are defined by considering the indentation projection shape as an ellipse. The major axis of the elliptical indentation was parallel to [0001]. This indentation shape anisotropy decreases as the Y concentration increases, and the indentation shape approaches a circle. Similar results have been confirmed by Vickers Indentation.

A slip line from the end of the major axis to the left and right was confirmed, which is considered to be a bottom slip. On the other hand, the generation of {10-12} twins was confirmed from the vicinity of the end of the minor axis, and it developed significantly with Pure Mg, but not so much with the Y additive. Similar results have been reported in studies using Brinell and Vickers indentations.

FIG. 17 shows Pure Mg, Mg-1.3 at. % Y and Mg-2.3 at. The major axis (d _L ), minor axis ( _ds ) and the difference between the major axis and the minor axis (Δd = d _{L− ds} ) measured from the in-situ observation image at each indentation load of each indentation test using% Y. It is a figure which shows. The data points plotted in the solid line frame in the figure (to the right of the load of 9.8 N) are scanning electron microscopes that measure the semimajor and uniaxial dimensions of the indentation remaining on the surface of the specimen after unloading. It is a value measured by (FE-SEM).

Since there is no indenter-refractive index adjusting liquid interface in the indenter contact region, no refraction of light occurs there. Major axis in the same load with increasing concentration of Y (d _L) and the minor axis (d _s) was decreased.
A smaller indentation diameter means an increase in hardness, that is, strengthening by Y solid solution. Major axis even in 1.0N as low load under which plastic deformation starts (d _L) and the minor axis (d _s) despite the decreases with increasing concentration of Y, [Delta] d is a large difference between each composition Not shown.
On the other hand, the amount of increase in Δd with the increase in the pushing load decreased with the increase in the Y concentration. As a result, Δd at a pushing load of 9.8 N decreased as the Y concentration increased. This means a decrease in indentation shape anisotropy due to the addition of Y described above. As already mentioned, bottom slip and {10-12} twins were confirmed as the plastic deformation mechanism activated during microindentation, and the activity of {10-12} twins decreased as the Y concentration increased. To do. This result is in good agreement with previous studies.

In the previous study by Vickers indentation using Mg-Y alloy single crystal, the activity of column surface slip near the indentation was confirmed. At that time, it has been reported that the shape anisotropy of the Vickers indentation decreases and the activity of {10-12} twins decreases as the Y concentration increases, and the Mg-Y alloy single crystal It is concluded that not only {10-12} twins but also columnar slips contribute significantly to the formation of indentations, and as a result, the indentation shape anisotropy is reduced. It is presumed that the decrease in indentation shape anisotropy due to the addition of Y in the present invention is due to the same reason as in the previous study by Vickers indentation.

Major axis in the (d _L) from the much smaller minor diameter (d _s) side indentation vicinity of the specimen surface, narrowing Do "sink size leaving no permanent deformation as indentations and the elastic behavior (Sink-in) It is expected that an area has arisen. In fact, in the in-situ observation image of the microindentation test, concentric Newton rings were observed only near the outermost edge of the indentation on the minor axis ( _ds ) side. This indicates that the distance between the indenter and the surface of the test piece gradually changes outside the outermost indentation on the minor axis ( _ds ) side, and therefore, the test near the indentation on the minor axis side. It is concluded that there is a "sink-in" on the body surface. In this way, by using this microindentation method, it has become possible to clarify the formation process of elliptical indentations.

FIG. 18 is a constitutive equation of the material by the indenter contact test, that is, a stress-strain curve in indenter mechanics. Representative stress in indenter mechanics, as the load average contact pressure load divided by the projected contact area _{p m (= P / A)} , also representative distortion, spherical indenter contact diameter d of the contact circle obtained by dividing the indenter radius r It is defined as the strain ε (= d / r). In this example, since the contact area is an ellipse rather than a perfect circle, the contact strain is defined by the value (d _L / r) obtained by dividing the semimajor axis d _{L of the} ellipse by the indenter radius r (= 500 microns).

The relationship between the average contact pressure and the indenter contact strain is given by the following equation.

(6), when the contact is limited only to the elastic deformation region (so-called Hertzian contact) the average vertical axis contact pressure p _m, the origin if plotted indenter contact strain d / r on the horizontal axis It has a linear relationship through which it passes, and since its slope is the product of Young's modulus and a constant, it means that the slope is constant. Therefore, the deviation point from the linear relationship is the elastic limit, and the deviation from the linear relationship indicates the degree of plastic deformation.

The stress-strain curve of FIG. 18 shows the linear relationship of the equation (6) in which the synthetic Young's modulus E ^* in the equation (6) is 44.5 GPa. The experimental points obtained with the above three types of test specimens show the non-linearity of the stress-strain relationship that deviates significantly from the straight line. Each plot on the stress-strain curve shows that the bottom slip and twinned plastic deformation behavior clearly observed under the microscope dominate the total deformation.

In the case of a single crystal of magnesium (Pure Mg), as shown in FIG. 16, since the surface of the test piece can be observed in detail, bottom slip and twins are generated under a load of only 1N, and they are further developed. The behavior was able to be determined microscopically. When this load level is converted into stress and strain, the stress is 197 MPa and the strain is 18.5%, and in the stress-strain curve of FIG. 18, it can be seen that the deformation behavior is in the completely plastic region. ..

FIG. 19 is a plot of a "scale of plastic deformation" calculated according to the analysis method described in Patent Document 2. In microscopic indentation, which can quantitatively measure the contact area under load, deformation behavior analysis based on the contact area is possible, and it can be separated into "elasticity" and "plasticity". In FIG. 19, the right end means perfect plasticity. Therefore, when an indentation load is applied in the direction parallel to [1-210], the magnesium (Pure Mg) single crystal whose experimental point is on the upper right is a magnesium alloy (Mg-1.3at.% Y, Mg-. Plastic deformation accounts for a larger proportion of the total deformation than a single crystal of 2.3 at.% Y). On the contrary, as the amount of yttrium Y added increases, the degree of solid solution strengthening acts strongly, the elastic property in the total deformation increases, and the plot moves toward the lower left.

FIG. 20 shows an image (top) observed in-situ with a single crystal of magnesium (Pure Mg) as a test body in a completely unloaded state after the completion of the microindentation test, and a scanning electron microscope on the surface of the test body after the test. It is a comparison with the image (FE-SEM / EBSD) (bottom).

In FIG. 20, the interface between the matrix and the {10-12} twin is shown by a black line. From the figure, surface undulations with a narrow region were observed just below the indenter as the pushing load decreased. Surface undulations with similar narrow regions were also observed from the FE-SEM image, but EBSD measurements revealed that this region had the same crystal orientation as the parent phase.

In previous studies by compression test and tensile test using Mg alloy, Detwinning of {10-12} twins was reported at the time of unloading or under load of reverse stress such as tensile stress after load of compressive stress. .. Therefore, this region is due to the shrinkage of {10-12} twins during unloading, that is, Detwinning, even under complex stress-deformation conditions such as deformation just below the indentation during the indentation test. Has occurred, and its behavior can be observed in a microindentation test.

This microscopic indentation method enables in-situ observation of the plastic deformation behavior on the surface of the specimen directly under the indenter and near the indenter contact region, and can be said to be very effective in discussing the plastic deformation behavior of the material.

By using a device and an observation method for observing the surface of the specimen during the loading process of the indentation test, the stress-strain curve, which is the constitutive equation of the material, can be measured more easily than the conventional macro test, and at the same time, various deformations can be measured. Behavior and fracture behavior can be quantified with high accuracy. This means that the deformation mechanism and the fracture mechanism can be discussed quickly and in detail.

Although the preferred embodiments of the present invention have been described in detail above, the present invention is not limited to the specific embodiment, and various modifications are made within the scope of the gist of the present invention described in the claims. , Can be changed.

1 Microscopic indentation tester 2 Measurement control device 3 Microscope 4 Transparent indenter 5 Specimen 6 Information processing device 7 Video camera 8 Positioning device 9 Load measurement device 10 Input / output I / F
11 Image analysis unit 12 CPU
13 Condition setting unit 14 Characteristic value calculation unit 15 Storage device 16 Device control unit 17 Objective lens 18 Testing machine frame 19 Transparent indenter holding plate 20 Refractive index adjusting liquid 30 Acute angle indenter 31 Spherical indenter 32 Condensing angle 33 Radius

Claims (17)

An observation device for observing the surface of a test piece when a load is applied to the surface of the test piece using a transparent indenter that transmits light of a specific wavelength.
A pressurizing means for applying a load to the test piece and
A load measuring means for measuring the load and
It has an imaging means for imaging the surface of the test body to which a load is applied by the pressurizing means.
The imaging means photographs the test piece through the transparent indenter.
The observation is
(1) Observation of surface shape, twins or dislocations and / and cracks,
(2) Observation to elucidate the mechanism of shape memory alloy,
(3) Observation for screening in alloy development,
(4) Observation to elucidate the stress-induced transformation mechanism,
(5) Observation of fracture and exfoliation of the surface brittle phase,
It is at least one selected from the group consisting of (6) observations for grasping wear characteristics imitating ball-on-disc scratches and (7) observations for evaluating thin film adhesion imitating ball-on-disc scratches.
A liquid is present in the gap between the transparent indenter and the surface of the test piece.
An observation device characterized in that the refractive indexes of the transparent indenter and the liquid are substantially equal when measured at 25 ± 5 ° C. using light having a predetermined wavelength. The value of the ratio of the refractive index of the transparent indenter to the refractive index of the liquid is 1.0: 1.0 ± 0.2 when measured at 25 ± 5 ° C. using light of a predetermined wavelength. The observation device according to claim 1, wherein the observation device is provided. The observation device according to claim 1 or 2, further comprising an optical characteristic observation means. The observation device according to any one of claims 1 to 3, further comprising a measuring means for measuring the state of the test piece based on the observation result. The observation device according to claim 4, wherein the measuring means measures a state of the test body in which the surface shape is a shape in which the surface of the test body is subducted or raised. The measuring means is of the twin or dislocation and / and crack.
The observation device according to claim 4, wherein the position and orientation are measured. The measuring means is characterized in that it measures the press-fitting depth of the transparent indenter and / or the contact area between the transparent indenter and the sample surface when a load is applied to the surface of the test piece using the transparent indenter. Item 4. The observation device according to item 4. An observation method for observing the surface of a test piece when a load is applied to the surface of the test piece using a transparent indenter that transmits light of a specific wavelength.
A pressurizing means for applying a load to the test piece and
A load measuring means for measuring the load and
Using the imaging means for imaging the surface of the test body to which the load is applied by the pressurizing means,
A liquid is allowed to exist in the gap between the transparent indenter and the surface of the test piece.
The refractive indexes of the transparent indenter and the liquid are substantially equal when measured at 25 ± 5 ° C. using light of a predetermined wavelength.
The test piece is imaged through the transparent indenter by the imaging means.
(1) Observation of surface shape, twins or dislocations and / and cracks,
(2) Observation to elucidate the mechanism of shape memory alloy,
(3) Observation for screening in alloy development,
(4) Observation to elucidate the stress-induced transformation mechanism,
(5) Observation of fracture and exfoliation of the surface brittle phase,
Observe at least one selected from the group consisting of (6) observations for grasping wear characteristics imitating ball-on-disc scratches and (7) observations for evaluating thin film adhesion imitating ball-on-disc scratches. An observation method characterized by. The value of the ratio of the refractive index of the transparent indenter to the refractive index of the liquid is 1.0: 1.0 ± 0.2 when measured at 25 ± 5 ° C. using light of a predetermined wavelength. The observation method according to claim 8, wherein the observation method is performed. The observation method according to claim 8 or 9, further comprising observing the optical characteristics of the test piece using an optical property observing means. The observation method according to any one of claims 8 to 10, further comprising measuring the state of the test piece by using a measuring means for measuring the state of the test piece based on the observation result. .. The observation method according to claim 11, wherein the measuring means measures the state of the test body in which the surface of the test body is a shape in which the surface of the test body is subducted or raised. By the measuring means, the twins or dislocations and / and the cracks
The observation method according to claim 11, wherein the position and orientation are measured. A claim characterized by measuring the press-fitting depth of the transparent indenter and / or the contact area between the transparent indenter and the sample surface when a load is applied to the surface of the test piece using the transparent indenter by the measuring means. Item 10. The observation method according to Item 11. A program used in the observation device of claim 1.
On the computer
A step of imaging the surface of the test body by the imaging means,
The state of the test piece, which is the shape in which the surface of the test piece is subducted or raised according to claim 5, by the image analysis unit based on the image of the surface of the test piece taken, and / and claim 6. A moving image analysis program for executing a step of moving image analysis of the position and orientation of the twin or dislocation and / and the crack according to claim 7, and the contact area between the transparent indenter and the sample surface according to claim 7. .. A program used in the observation device of claim 1.
On the computer
Steps to accept various test conditions entered by the user,
Steps to drive the precision positioning device based on the various test conditions received,
A device control program for executing a step of controlling a load applied to the surface of the test piece by the pressurizing means by using the transparent indenter through the driving of the precision positioning means. A program used in the observation device of claim 1.
On the computer
A step of imaging the surface of the test body by the imaging means,
Based on the image of the surface of the test piece taken, the value obtained by measuring the state of the test piece according to claim 5 by the observation device and the twin crystal or dislocation or / and crack according to claim 6. A characteristic value calculation program for executing a step of calculating the characteristic value of the test piece from the position and orientation, the press-fitting depth of the transparent indenter according to claim 7, and / or the contact area between the transparent indenter and the sample surface.