CN115112697A - A Microstrain Characterization Method for Magnesium Alloys - Google Patents

Abstract

The invention discloses a magnesium alloy micro-strain characterization method, which comprises the following steps: step 1, grinding the surface of a magnesium alloy piece; step 2, performing electrolytic polishing on the ground magnesium alloy piece, the electrolytic polishing solution is ACII solution, and the electrolytic polishing solution is ACII solution. The polishing temperature is -35~-25°C, and the electropolishing time is 90~150s; in step 3, the surface of the magnesium alloy part is corroded by using the ACII solution containing Fe ³⁺ , the corrosion temperature is -35~-25°C, and the corrosion time is 5~ For 20 s, nano-scale speckles were obtained on the surface of magnesium alloys. It can make uniformly distributed nano-scale speckles on the surface of magnesium alloy, and then can obtain a high-resolution strain map on the grain scale of magnesium alloy without disturbing the EBSD measurement signal.

Description

A Microstrain Characterization Method for Magnesium Alloys

technical field

The invention relates to the field of micro-strain in the deformation process of magnesium alloys, in particular to a method for characterizing micro-strains of magnesium alloys.

Background technique

Magnesium alloys have low density, high specific strength, excellent shock absorption and electromagnetic shielding properties, and have great application prospects as lightweight materials and functional materials. However, the commonly used magnesium alloys have a close-packed hexagonal crystal structure, which has fewer activated slip systems and poor plasticity at room temperature. An in-depth study of the microscopic deformation mechanism of magnesium alloys is crucial for optimizing their mechanical properties. Since non-basal slip has a higher critical shear stress than basal slip or twinning, basal slip and twinning are the main deformation mechanisms of magnesium alloys at room temperature, which makes the plastic deformation of single crystal magnesium very strong anisotropy, which leads to deformation incompatibility between grains during deformation of polycrystalline magnesium alloys. And this deformation incompatibility can be adjusted to a certain extent to maintain a certain plasticity. In addition, compared with the face-centered or body-centered cubic crystal structures of highly symmetrical materials, such as copper, aluminum, and steel, magnesium alloys tend to develop stronger textures during hot working, leading to their subsequent loading during the loading process. The mechanical properties have obvious anisotropy. How to quantitatively evaluate the slip at the micro-scale, the relationship between crystal orientation and inter-grain deformation coordination is a major challenge in the plastic deformation process of magnesium alloys.

Using electron backscatter diffraction (EBSD) technique to obtain crystal misorientation data, the geometrically necessary dislocation density generated during deformation can be calculated, and some activated slip systems can be determined by crystal misorientation axis or slip trace matching, But they do not provide data on deformation kinematics. Therefore, the EBSD technique cannot be used to quantify local plastic strain. As a powerful tool, digital image correlation technique DIC plays a crucial role in the quantitative measurement of strain fields in two-dimensional planes. Using EBSD measurement combined with DIC technique to characterize the plastic deformation of materials can comprehensively reflect the connection between crystallography and deformation kinematics. The basic principle of DIC technology measurement is to track and identify the speckle on the surface of the material before and after deformation based on the corresponding image matching algorithm, and obtain the tensor maps of the ɛxx, ɛyy and ɛxy strain fields. Therefore, the fineness of the strain depends on the preparation of the speckles. the size of. In previous studies, DIC techniques have typically focused on strain distributions with millimeter-scale spatial resolution. However, this resolution is insufficient to quantify the microstructural features during deformation. In recent years, the development of surface fine speckle preparation methods such as surface fine speckle preparation methods include surface self-dispersion of nanoparticles, electron/ion beam etching, Pt deposition, gold plating, etc., which has promoted the rise of high-resolution DIC technology. , the technique can be used to measure strain on the micrometer or submicrometer scale. Although the preparation method of these speckles can greatly improve the spatial resolution of strain, the complicated preparation steps or high cost still limit their wide application.

SUMMARY OF THE INVENTION

The purpose of the present invention is to provide a micro-strain characterization method of magnesium alloy, which can obtain uniformly distributed nano-scale speckles on the surface of magnesium alloy, and then can obtain magnesium alloy grain size on the premise of not disturbing the EBSD measurement signal. high-resolution strain map.

The magnesium alloy micro-strain characterization method of the present invention comprises the following steps:

Step 1, grinding the surface of magnesium alloy parts;

In step 2, electropolishing is performed on the ground magnesium alloy parts, the electropolishing solution is ACII solution, the electropolishing temperature is -35~-25°C, and the electropolishing time is 90~150s;

Step 3, using ACII solution containing Fe ³⁺ to corrode the surface of magnesium alloy parts, the corrosion temperature is -35~-25 ℃, and the corrosion time is 5~20s, and nano-scale speckles are obtained on the surface of magnesium alloy.

Further, each liter of the ACII solution includes the following components: 15~20mL of distilled water, 90~100mL of propanol, 8~12g of hydroxyquinoline, 70~80g of citric acid, 40~45g of thiocyanate sodium, 10-15 mL of perchloric acid, and the balance is ethanol.

Further, the preparation of the ACII solution containing Fe ³⁺ is as follows: 0.3-0.6 g of anhydrous FeCl ₃ is placed in 50-100 mL of the ACII solution to dissolve.

Further, the etching in the third step is carried out under the condition of magnetic stirring.

Compared with the prior art, the present invention has the following beneficial effects.

1. In the present invention, the ground magnesium alloy parts are subjected to electrolytic polishing treatment, and then the surface of the magnesium alloy parts is corroded by an ACII solution containing Fe ³⁺ , the process parameters of electrolytic polishing and corrosion are limited, and uniform distribution is obtained on the surface of the magnesium alloy. The size of the speckle is nanoscale, and the speckle covers a wide area, so that the high-resolution strain map on the grain scale of magnesium alloy can be obtained without disturbing the EBSD measurement signal.

2. The present invention has simple technological process, easy preparation, low cost and wide application range.

Description of drawings

Fig. 1 is the SEM image of nano-scale speckle on the surface of magnesium alloy according to the present invention;

Fig. 2 is the partial enlarged schematic diagram of Fig. 1;

Fig. 3 is the orientation distribution schematic diagram of magnesium alloy under the splicing area;

Figure 4 is a schematic diagram of the high-resolution strain distribution processed by DIC technology.

Detailed ways

The present invention will be described in detail below with reference to the accompanying drawings.

A magnesium alloy micro-strain characterization method, comprising the following steps:

Step 1: Grinding the surface of magnesium alloy parts: 400#, 800#, 1200#, 1400#, 2000# sandpapers are used to grind the Mg-13Gd extruded plate in turn until the surface of the Mg-13Gd extruded plate is bright.

In step 2, electropolishing is performed on the ground magnesium alloy parts, the electropolishing temperature is -30°C, and the electropolishing time is 120s. Electrolytic polishing solution is ACII solution,

Each liter of the ACII solution includes the following components: 18.5 mL of distilled water, 100 mL of propanol, 10 g of hydroxyquinoline, 75 g of citric acid, 41.5 g of sodium thiocyanate, 15 mL of perchloric acid, and the remainder. The amount is ethanol. When preparing, first mix ethanol and distilled water, then add propanol, hydroxyquinoline, citric acid, sodium thiocyanate and perchloric acid in sequence, and then add the next component after the previous component is completely dissolved.

Step 3, using ACII solution containing Fe ³⁺ to corrode the surface of the magnesium alloy piece, the corrosion temperature is -25°C, and the corrosion time is 5s, to obtain nano-scale speckles on the surface of the magnesium alloy.

The ACII solution containing Fe ³⁺ was prepared as follows: 75 mL of ACII solution was poured into a beaker, and then 0.4 g of anhydrous FeCl ₃ was placed in the ACII solution to dissolve.

The corrosion process is carried out under the condition of magnetic stirring, and the rotating speed is 200-800 rpm; preferably, the rotating speed is 500 rpm.

Referring to Figure 1 and Figure 2, the size and morphology distribution of the nano-scale speckles prepared on the Mg-13Gd extruded plate were observed by field emission scanning electron microscopy. The speckle is evenly distributed and the size of the speckle is at the nanometer level, and the speckle covers a wide area.

VIC 2D software was used to track and identify the speckle in the SEM images before and after deformation at 6000 times, and a high-resolution strain map at the grain scale of a single SEM image was obtained. Then, multiple high-resolution strain maps are spliced to obtain a high-resolution strain map with sufficient grain numbers, see Figure 3. The EBSD measurement was carried out with a field emission scanning electron microscope, and the orientation distribution map of the Mg-13Gd extruded plate as shown in Fig. 4 was obtained. It is shown that the prepared nano-scale speckles can obtain high-resolution strain maps on the grain scale of magnesium alloys without disturbing the EBSD measurement signal.

Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and not to limit them. Although the present invention has been described in detail through the above preferred embodiments, those skilled in the art should Various changes may be made in details without departing from the scope of the invention as defined by the claims.

Claims (4)

1. a magnesium alloy micro-strain characterization method, is characterized in that, comprises the steps: Step 1, grinding the surface of magnesium alloy parts; In step 2, electropolishing is performed on the ground magnesium alloy parts, the electropolishing solution is ACII solution, the electropolishing temperature is -35~-25°C, and the electropolishing time is 90~150s; Step 3, using ACII solution containing Fe ³⁺ to corrode the surface of magnesium alloy parts, the corrosion temperature is -35~-25 ℃, and the corrosion time is 5~20s, and nano-scale speckles are obtained on the surface of magnesium alloy. 2. The magnesium alloy micro-strain characterizing method according to claim 1, wherein the ACII solution comprises the following components in every liter: distilled water of 15～20mL, propanol of 90～100mL, 8～12g hydroxyquinoline, 70~80g of citric acid, 40~45g of sodium thiocyanate, 10~15mL of perchloric acid, and the balance is ethanol. 3. The magnesium alloy micro-strain characterization method according to claim 1 or 2, wherein the preparation of the ACII solution containing Fe ³⁺ is: placing 0.3-0.6 g of anhydrous FeCl ₃ in 50-100 mL dissolved in the ACII solution. 4. The magnesium alloy micro-strain characterization method according to claim 1 or 2, wherein the corrosion in the third step is carried out under magnetic stirring conditions.

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