CN101811186B - Device for driving solidification and crystallization process by using electrical effect - Google Patents

Abstract

The invention relates to a device for driving a solidification and crystallization process by using electrical effect, relating to a solidification and crystallization device, and solving the problem that a traditional device for observing the crystallization behavior of a crystal under an electric field can not intuitively observe the growth condition of the crystal. The device for driving the solidification and crystallization process by using the electrical effect comprises an electric field generating system, a constant-temperature water circulation system, a crystallizer, a CCD (Charge Coupled Device) microscope, a thermal resistor, a communication instrument, a serial communication port, a USB bus interface circuit and a computer. The anode of the electric field generating system is connected with one end of the crystallizer, and the cathode of the electric field generating system is connected with the other end of the crystallizer. The constant-temperature water circulation system is communicated with the crystallizer to ensure the temperature of the crystallizer to be constant. The CCD microscope is arranged right above the crystallizer and is connected with the computer through the USB bus interface circuit. The film platinum thermal resistor is arranged in the melting zone of the crystallizer in advance, and is connected with the data input end of the communication instrument, and the data output end of the communication instrument is connected with the computer through the serial communication port. The invention is suitable for the condition that the crystallization process is needed to be directly observed.

Description

A device for driving the solidification and crystallization process by electric effect

technical field

The invention relates to a device for solidifying and crystallizing.

Background technique

Since the beginning of the 21st century, high-tech industries, especially aviation, aerospace and automobile industries, have become more and more demanding on the use of materials. Scientists are eagerly looking forward to seeking new materials with excellent performance by controlling the solidification process of materials. In-depth research has been carried out on the control of material solidification process under the action of external fields such as microgravity field, electric field, magnetic field, electromagnetic field and ultrasonic waves, and fruitful results have been obtained. Among them, the coagulation technology under the action of an electric field has the advantages of simple equipment, easy operation, and obvious changes in the coagulation structure, which has received great attention.

The research on the solidification process of materials under the action of an electric field began in the 1960s, and it has been nearly half a century. A large number of experimental data have confirmed that the electric field can increase the temperature gradient at the front of the solid-liquid (S/L) interface of metals and their alloys during solidification. , affecting its crystal growth and refining the solidification structure. The influence mechanism of electric field on the solidification of metals and their alloys can be considered from the following points: (1) electric field thermal effect or thermoelectric effect (including Joule thermal effect, Seebeck effect, Peltier effect, Thomson effect); (2) electromigration; (3) electric field The induced Lorentz force drives the melt flow. The thermal effect directly affects the temperature field at the S/L interface, resulting in the change of the temperature gradient in the solidification direction at the S/L interface. Electromigration affects the solidification solute partition coefficient. The flow of the liquid phase before the solidification of the metal affects the heat transfer, mass transfer and momentum transfer processes during the solidification process. The three restrict each other, and the coupling relationship is shown in Figure 1.

In order to intuitively characterize the solidification behavior characteristics of metals and their alloys, including solute redistribution and dendrite tip growth, and deeply reveal the essential characteristics of material solidification, researchers continue to update observation and analysis methods.

The researchers applied various forms of electric fields to the alloy melt stage, common solidification conditions, directional solidification conditions and post-solidification heat treatment. The selected materials include Pb-Sn, Zn alloys, Al alloys, cast iron, stainless steel, high manganese steel, For magnesium alloys, the experimental results of the electric field affecting the solidification process and changing the solidification structure of the metal were obtained respectively. Scholars have also conducted in-depth research on the solidification mechanism of metals under the action of an electric field.

When Gu Genda applied a steady electric field parallel to the growth direction to Al–4.5 wt.% Cu and Sn–5 wt.% Bi alloys under directional solidification conditions, the interface electrostatic potential, interface voltage and electric field strength, and the interface atomic After the relationship between the hopping probability and the interface electric field, the electric field energy of the solute and the interface energy, and the energy state of the atoms on both sides of the solid and liquid, the final quantitative relational expression of the interface partition coefficient under the electric field when the growth rate is zero is given. The analysis shows that the interface partition coefficient of the alloy decreases with the increase of the current density; the direct current electric field significantly improves the interface stability of the Sn-5%wt.Bi alloy, and its effect is manifested in the plane interface → unstable interface → cell crystal The critical growth rate of interface→dendrite interface transition increases rapidly with the increase of current density. It is considered that the main reason for the rapid increase of interface stability caused by electric field is that the electric field increases the interface energy and the frequency of the most dangerous interference wave on the interface and the electric field causes the increase of convection in the liquid phase. Shanghai University studied the influence of pulse electric field on the morphology of solid-liquid interface of pure Al and Al alloy under the condition of directional solidification. By passing pulse current at the upper and lower ends of Al-4.5 wt.% Cu alloy, it was found that: with the increase of pulse current density increase, the distance between the alloy cell grains and the depth of the mushy zone decreases, and the morphology of the solid-liquid interface changes from dendrite to cell crystal or even a flat interface. The pulse current increases the temperature gradient at the front of the solid-liquid interface, which promotes a more uniform solute distribution. , the secondary dendrite growth is inhibited. It is well known that in the directional solidification process of metals, the solid-liquid interface is an important factor determining the solidification of materials, which has an important impact on the solute distribution, crystal morphology, and organizational structure of materials, and then determines the properties of solidified materials. The solidification behavior at the front of the solidification interface, changing the distribution of solutes, and affecting the temperature gradient at the front of the solid-liquid interface will surely play an important role.

The research on applying direct current and alternating current to the casting solidification process began in the 1960s. At that time, it was found that the final solidification structure of the Al-Ni alloy melt passed through the current changed, especially the effective solute distribution coefficient changed. Crystalline alloys promote the separation or segregation of the two constituent phases. Immediately after the former Soviet Union applied current to cast iron solidification in the 1970s, it showed that the average size of the graphite phase was reduced by 20%-40%, and the graphite phase changed from flake to curl, and the tensile strength increased by 30%. After entering the 1980s, the American scholar A.K.Misra introduced a direct current into the solidification of the Pb-Sb-Sn ternary alloy, and obtained a fine and uniform solidification structure, and the eutectic layer spacing was also reduced to 1/4 of the original, and the eutectic The number of clumps increased, which fully verified the hypothesis that the current promotes nucleation and inhibits growth. Since the 1990s, scholars at home and abroad have initially confirmed that the current density and the primary dendrite spacing are linearly inversely proportional, and a high current density is conducive to increasing the Joule heat difference between the solid-liquid two phases at the solidification front, increasing the interface energy, and increasing the temperature gradient. This increases the stability of the solidification interface.

However, in order to obtain high current density, common current technology needs to be guaranteed by quite reliable high-power power facilities, which is expensive and unfavorable for practical application. It has been discovered that pulsed current (electric pulse) can implement intermittent large energy output through power equipment with low power and small investment. Since then, the influence of electric pulse on metal solidification structure has become a new research direction. Professor M.C.Flemings of the Massachusetts Institute of Technology and others took the lead in studying the application of pulse current during alloy casting. They used a low melting point Sn-15%Pb alloy melt and found that applying pulse current at the initial stage of solidification can make The dendrites in the organization transform into spherical crystals, and the morphology depends on the discharge peak voltage, solid phase volume fraction and solidification cooling rate; they also observed the fluctuation of the metal liquid level, confirming the stretching force caused by the pulse current charging and discharging process. The presence.

Which mechanism plays a leading role in controlling solidification depends on the physical properties and composition of different materials, and cannot be generalized. Solidification is a transformation process of a complex energy system, accompanied by heat transfer, mass transfer, and momentum transfer Therefore, it is urgent to simplify the solidification process, filter out irrelevant factors, and focus on the mechanism of a certain effect of the electric field on the metal solidification process.

In terms of crystal growth observation, it can be seen from the existing literature that most of them are studies on the solidification and crystallization behavior of some model alloys under no electric field, such as the self-made device of Northwestern Polytechnical University: a strip composed of 4 glass slides In the space, copper sheets of the same thickness are inserted on both sides, and then seamlessly bonded with transparent organic glue, and the shadow part is the model alloy. The temperature control system precisely adjusts the temperature gradient in the growth chamber through the copper sheet to obtain different crystal growth shapes.

However, the device for directly observing the crystal growth under the electric field under the microscope has not been reported yet.

Contents of the invention

In order to solve the problem that the existing device for observing the crystallization behavior cannot directly observe the crystal growth under the action of an electric field, the present invention provides a device for driving the solidification and crystallization process by electric effect.

A device for driving the solidification and crystallization process by electric effect, which includes an electric field generating system, a constant temperature water circulation system, a crystallizer, a CCD microscope, a thermal resistance, a communication instrument, a serial communication port, a USB bus interface circuit and a computer;

The positive electrode of the electric field generating system is connected to the hot end of the crystallizer, the negative electrode of the electric field generating system is connected to the cold end of the crystallizer, and the constant temperature water circulation system is connected to the crystallizer to ensure that the temperature of the crystallizer is constant. Directly above, and connected to the data communication terminal of the computer through the USB bus interface circuit, the thin-film platinum thermal resistance is preset in the melting zone of the crystallizer, and connected to the data input terminal of the communication instrument, and the data output terminal of the communication instrument is connected through serial communication The port is connected to the data communication port of the computer.

The device of the present invention can directly observe the crystal growth process with crystal growth characteristics of small crystal planes or non-small crystal plane crystal growth characteristics, control the temperature gradient and apply a steady electric field, an alternating electric field and a pulsed electric field to act on the crystal growth process, and finally The preparation of crystal solidification samples under the action of an electric field can lay a foundation for theoretical research on the solidification behavior of materials under an external field and enrich the connotation of the subject of non-equilibrium solidification of materials.

The invention is a device directly used for observing crystallization behavior under an electric field. The device has the advantages of real-time temperature measurement and recording, dynamic photo and video recording, controllable electric field size and direction parameters, stable output, large temperature gradient, and small volume. . The present invention is applicable to the situation where the crystallization process needs to be observed directly.

Description of drawings

Fig. 1 is a schematic diagram of the coupling effect of an electric field on a metal material. Fig. 2 is a schematic structural diagram of a device for driving the solidification and crystallization process by electric effect. FIG. 3 is a partially enlarged schematic diagram of the dotted ellipse in FIG. 2 . Fig. 4 is a photograph of columnar dendrite growth during solidification of a succinonitrile-based metal model alloy in the absence of an electric field. Fig. 5 is a photograph of columnar dendrite growth during solidification of a succinonitrile-based metal model alloy under a steady electric field. Fig. 6 is the temperature change curve of the melting zone during the crystallization process of NH ₄ Cl crystals. Fig. 7 is a photograph of dendrite growth in the melting zone of NH ₄ Cl crystals during crystallization for 400s. Fig. 8 is a photograph of dendrite growth in the melting zone of NH ₄ Cl crystals at 422s of crystallization. Fig. 9 is a photo of columnar dendrite growth during directional solidification of a succinonitrile-based metal model alloy in the absence of an electric field. Fig. 10 is a photograph of columnar dendrite growth during directional solidification of a succinonitrile-based metal model alloy under a steady electric field. Fig. 11 is a photograph of cell crystal growth when the succinonitrile-based metal model alloy is solidified in the absence of an electric field. Fig. 12 is a photograph of cell crystal growth when the succinonitrile-based metal model alloy is solidified under a steady electric field. Fig. 13 is a flowchart of the working principle of direct observation of crystal growth under electric field by using the device of the present invention. FIG. 13 is a top view of the crystallizer 103 . Fig. 14 is a flowchart of the working principle of direct observation of crystal growth under electric field under a microscope.

Detailed ways

Specific Embodiments 1. This embodiment is described in conjunction with FIG. 2, a device for driving the solidification and crystallization process by electric effect, which includes an electric field generating system 101, a constant temperature water circulation system 102, a crystallizer 103, a CCD microscope 4, a thermal resistance 5, and a communication instrument 7. Serial communication port 8, USB bus interface circuit 11 and computer 12;

The positive pole of the electric field generating system 101 is connected to the hot end of the crystallizer 103, the negative pole of the electric field generating system 101 is connected to the cold end of the crystallizer 103, and the constant temperature water circulation system 102 is connected to the crystallizer 103 to ensure that the temperature of the crystallizer 103 is constant. The CCD microscope 4 is arranged directly above the crystallizer 103, and is connected to the data communication terminal of the computer 12 through the USB bus interface circuit 11, and the thin-film platinum thermal resistance 5 is preset in the crystallizer melting zone 30, and communicates with the data of the instrument 7. The input end is connected, and the data output end of the communication instrument 7 is connected with the data communication end of the computer 12 through the serial communication port 8 .

Specific embodiment 2. This embodiment is described in conjunction with FIG. 3. This embodiment is a further description of specific embodiment 1. The electric field generating system 101 includes a sensitive ammeter 1 and a power supply 10;

The constant temperature water circulation system 102 includes a constant temperature water circulation system at the cold end of the melting zone, a constant temperature water circulation system at the vertical electrode of the melting zone, and a constant temperature water circulation system at the hot end of the melting zone;

The crystallizer 103 includes a melting zone 30, a melting zone hot end electrode insert 29, a melting zone cold end electrode inserting plate 34, an upper vertical electrode 33, a lower vertical electrode 21, a melting zone hot end heat transfer block 27, a melting zone cooling End heat transfer block 36, vertical electrode upper end heat transfer tube 31, vertical electrode lower end heat transfer tube 20;

The melting zone 30 is a rectangular carbonate block with an internal cavity structure, and the internal cavity is covered by glass sheets on the upper and lower surfaces, a polycarbonate plate, and an end face of the cold end electrode insertion plate 34 of the melting zone, and a hot end electrode. A long and narrow space constrained by an end face of the flashboard 29;

One end face of the hot end heat transfer block 27 of the melting zone is connected to an end face of the hot end electrode inserting plate 29 of the melting zone, and the other end face of the hot end electrode inserting plate 29 of the melting zone forms an end face of the melting zone 30, and the cold end of the melting zone One end face of the electrode inserting plate 34 constitutes the other end face of the melting zone 30, and the other end face of the cold end electrode inserting plate 34 of the melting zone is connected to an end face of the cold end heat transfer block 36 of the melting zone, and a transparent plate is placed in the melting zone 30. The metal-like alloy is vertical to the temperature gradient direction of the melting zone 30, and the other side of the melting zone 30 is provided with a lower vertical electrode 21, and the upper end heat transfer tube 31 of the vertical electrode is arranged on the surface of the upper vertical electrode 33, and the vertical electrode The lower end heat transfer tube 20 is arranged on the surface of the lower end vertical electrode 21;

The positive pole of the power supply 10 of the electric field generating system 101 is connected to the hot end electrode board 29 of the melting zone, the negative pole of the power supply 10 is connected to the cold end electrode board 34 of the melting zone, and the sensitive ammeter 1 is connected in series between the power supply 10 and the hot end of the melting zone. In the circuit formed by the electrode board 29 and the electrode board 34 at the cold end of the melting zone;

The constant temperature water circulation system at the hot end of the melting zone communicates with the heat transfer block 27 at the hot end of the melting zone of the electric field generating system 101, the constant temperature water circulation system at the cold end of the melting zone communicates with the heat transfer block 36 at the cold end of the melting zone of the electric field generating system 101, and the vertical electrodes in the melting zone The constant temperature water circulation system communicates with the upper vertical electrode 33 and the lower vertical electrode 21 of the electric field generating system 101 .

Specific Embodiment 3. This embodiment is described in conjunction with FIG. 3 . This embodiment is a further description of Specific Embodiment 2.

The constant temperature water circulation system at the hot end of the melting zone includes a water bath heating and temperature control module 23 at the hot end of the melting zone, a circulating water pump 24 for heating at the hot end of the melting zone, two circulation pipes 25 and a water bath 26 for heating at the hot end of the melting zone;

Both the heat transfer block 27 at the hot end of the melting zone and the heat transfer block 36 at the cold end of the melting zone have horseshoe-shaped communication grooves inside;

The temperature sensing part of the melting zone hot end water bath heating and temperature control module 23 is immersed in the melting zone hot end heating water bath 26, one end of a circulation pipe 25 is inserted into the melting zone hot end heating water bath 26, and one circulation pipe The other end of 25 communicates with one end of the groove of the heat transfer block 27 at the hot end of the melting zone. The other end of the pipe 25 communicates with the other end of the groove of the heat transfer block 27 at the hot end of the melting zone, and two circulating pipes 25 form a constant temperature circulation system to keep the temperature at the hot end of the melting zone constant;

The vertical electrode constant temperature water circulation system in the melting zone includes a vertical electrode water bath heating and temperature control module 18 in the melting zone, a vertical electrode heating circulating water pump 22 in the melting zone, three circulation pipes 25 and a vertical electrode heating water bath 19 in the melting zone;

The temperature sensing part of the melting zone vertical electrode water bath heating and temperature control module 18 is immersed in the melting zone vertical electrode heating water bath 19, one end of a circulation pipe 25 is inserted into the melting zone vertical electrode heating water bath 19, and a circulation pipe The other end of 25 communicates with one end of the heat transfer pipe 20 at the lower end of the vertical electrode, one end of the other circulation pipe 25 communicates with the other end of the heat transfer pipe 20 at the lower end of the vertical electrode, and the other end of the other circulation pipe 25 communicates with the vertical electrode lower end heat transfer pipe 20. One end of the heat transfer tube 31 at the upper end of the electrode is connected, one end of the third circulation pipe 25 is inserted into the vertical electrode heating water bath 19 of the melting zone through the vertical electrode heating circulation pump 22 of the melting zone, and the other end of the third circulation pipe 25 is connected to the vertical electrode heating water bath 19. The other end of the upper heat transfer tube 31 is connected, and the three circulation tubes 25 form a constant temperature circulation system to keep the temperature of the vertical electrodes in the melting zone constant;

The constant temperature water circulation system at the cold end of the melting zone includes a cold end water bath temperature control instrument 17, a water cooling circulating water pump 15 at the cold end of the melting zone, two circulation pipes 25 and a constant temperature water bath 16 at the cold end of the melting zone;

The temperature sensing part of the cold end water bath temperature control instrument 17 is immersed in the cold end constant temperature water bath 16 of the melting zone, one end of a circulation pipe 25 is inserted into the cold end constant temperature water bath 16 of the melting zone, the other end of a circulation pipe 25 is connected to the One end of the groove of the heat transfer block 36 at the cold end of the melting zone is connected, and one end of another circulation pipe 25 is inserted into the constant temperature water bath 16 at the cold end of the melting zone through the water-cooled circulating water pump 15 at the cold end of the melting zone, and the other end of the other circulation pipe 25 is connected to the melting zone. The other end of the groove of the heat transfer block 36 at the cold end of the zone is connected, and two circulating pipes 25 form a constant temperature circulation system to keep the temperature of the cold end of the melting zone constant;

Embodiment 4. The difference between this embodiment and Embodiment 3 is that the circulation pipe 25 is a plastic circulation pipe.

Embodiment 5. The difference between this embodiment and Embodiment 2 or 3 is that the heat transfer tube 31 at the upper end of the vertical electrode and the heat transfer tube 20 at the lower end of the vertical electrode are copper heat transfer tubes, and the heat transfer block 27 at the hot end of the melting zone and The heat transfer block 36 at the cold end of the melting zone is a copper heat transfer block.

Embodiment 6. The difference between this embodiment and Embodiment 3 is that the hot end water bath heating and temperature control module 23 in the melting zone is composed of a hot end heater 13-1 and a hot end water bath temperature control instrument 14-1. The signal input end of the hot end heater 13-1 is connected with the signal output end of the hot end water bath temperature control instrument 14;

The vertical electrode water bath heating and temperature control module 18 in the melting zone is composed of a vertical electrode heater 13-2 and a vertical electrode water bath temperature control instrument 14-2. The signal input terminal of the vertical electrode heater 13-2 is connected with the vertical electrode water bath temperature control The signal output terminal of instrument 14-2 is connected.

The specific embodiment seven, in conjunction with Fig. 2 and Fig. 3 illustrate this embodiment, this embodiment is to utilize above-mentioned device to directly observe the working principle of the crystal growth under the electric field under the microscope:

Step 1, forming a temperature gradient in the melting zone 30, the specific process is as follows:

The hot-end electrode board 29 of the melting zone and the cold-end electrode board 34 of the melting zone are connected to the power supply 10, the hot-end electrode board 29 of the melting zone and the cold-end electrode board 34 of the melting zone form a temperature gradient G _T , which is heated by the hot end of the melting zone The circulating water pump 24 circulates the heating water bath 26 at the hot end of the melting zone to the heat transfer block 27 at the hot end of the melting zone to form the hot end of the melting zone, and the water-cooled circulating water pump 15 circulates the constant temperature water bath 16 at the cold end of the melting zone to the cooling The end heat transfer block 36 forms the cold end of the melting zone;

The lower vertical electrode 21 and the upper vertical electrode 33 circulate through the vertical electrode heating circulation pump 22 in the melting zone to ensure that the temperature of the lower vertical electrode 21 and the upper vertical electrode 33 is consistent with the temperature when the crystal forms a melt in the melting zone 30;

Step 2, the hot-end electrode plug-in board 29 of the melting zone and the cold-end electrode plug-in board 34 of the melting zone are connected to the power supply 10 to form an electric field strength E parallel to the direction of the temperature gradient _GT , and the lower vertical electrode 21 and the upper vertical electrode 33 are connected to the power supply 10 to generate The electric field strength E' in the direction perpendicular to the temperature gradient G _T ;

Step 3, the CCD microscope 4 is set directly above the crystallizer 103, and the photo of the crystal growth in the melting zone 30 is taken in real time through the CCD microscope 4, and is transmitted to the USB bus interface circuit 11, and the computer 12 is used to save the photo of the crystal growth;

Step 4, connect the sensitive ammeter 1, the power supply 10, the hot-end electrode board 29 of the melting zone and the cold-end electrode board 34 of the melting zone to form a loop, and the preset thin-film platinum thermal resistance 5 directly measures the temperature of the melting zone 30, and Through the communication instrument 7, it is transmitted to the serial communication port 8, and the temperature is measured and recorded in real time.

Adjust the temperature of the heating water bath 26 at the hot end of the melting zone and the constant temperature water bath 16 at the cold end of the melting zone to control the crystal growth process in the melting zone 30 . Adjusting the current intensity I of the power supply 10 to output currents with different current densities can change the electric field intensity E applied parallel to the direction of the temperature gradient _GT and the E' applied in the direction perpendicular to the temperature gradient _GT , and act on the crystal solidification interface.

First observe the case where the direction of the electric field is perpendicular to the direction of the temperature gradient:

As shown in Figure 4, this photo was taken at the growth rate of directional solidification r=12.5μm/s, and the temperature gradient G _T =3.82k/mm. It is easy to see that the crystal is perpendicular to its growth direction. Under the action of an electric field, the growth of columnar dendrites appears to grow obliquely against the flow, indicating that the steady electric field in this direction has the effect of strengthening the flow of the liquid region at the front of the solidification interface.

As shown in Figure 5, this photo was taken at the growth rate of directional solidification r=13.4μm/s, the temperature gradient G _T = 3.56k/mm, and I=0.5mA. ₄ Cl columnar dendrite growth morphology found that: the direction of the electric field is approximately perpendicular to the growth direction of the primary arm. The white scale in the figure marks the size of the secondary arm. After 22s of electric field action, the primary arm of the columnar crystal grows rapidly, and the size of the secondary arm does not change much, indicating that its growth is inhibited. According to the analysis, the electric field perpendicular to the solidification direction can increase the temperature gradient in this direction and promote the heat flow along the primary arm to dissipate heat in one direction, thereby inhibiting the growth of dendrite side branches. The thermal effect of the electric field is quite effective in affecting the dendrite growth.

Figures 6 to 8 show the crystallization process of NH ₄ Cl crystals under a steady electric field. The applied current density is 22mA/mm ² , and the direction of the arrow is the direction of the electric field intensity E. As shown in Figure 6, for NH ₄ Cl melting The body was powered on and off twice in turn, and the influence of the stable electric field on the growth of NH ₄ Cl columnar dendrites was investigated. It can be seen from Fig. 7 and Fig. 8 that in Fig. 7 and Fig. 8, the right side is the end near the center of the melt, and the NH ₄ Cl crystal near the melt boundary is crystallized under the action of an electric field with a glass sheet as the crystallization substrate. Approximate directional solidification, its growth direction is approximately perpendicular to the direction of the electric field, that is, its primary arm dendrite stem is perpendicular to the direction of the electric field. After 22s in the crystal in Figure 8, it was found that the primary arm grew normally, but the size of the secondary arm did not change much, as shown in the white scale in the figure. According to the analysis, there is a large temperature gradient in the direction perpendicular to the electric field, that is, in the direction of solidification, which leads to the normal growth of the dendrite primary arm along the direction of heat flow; while in the direction parallel to the electric field, the temperature gradient is small, and the weak heat flow restricts the secondary arm. growth.

Then observe the case where the direction of the electric field is parallel to the direction of the temperature gradient:

Figure 9 is taken at the growth rate of directional solidification r=35.5μm/s, temperature gradient G _T = 3.96k/mm, and Figure 10 is at the growth rate of directional solidification r=25.0μm/s, temperature gradient G _T = 3.96k/mm, as shown in Figure 9 and Figure 10, when the direction of the electric field is parallel to the crystal growth direction, the growth of columnar dendrites of succinonitrile also shows that individual columnar dendrites bend and grow obliquely against the flow . Compared with Figure 7 and Figure 8, when the electric field direction is parallel, the solidification interface is macroscopically uneven, not as uniform as when the electric field is vertical. The dendrite secondary arms are more developed than when the electric field is vertical.

Figure 11 and Figure 12 are the crystallization growth process of succinonitrile alloy cellular dendrites under a steady electric field, Figure 11 is the case of directional solidification growth rate r=25.0μm/s, temperature gradient G _T = 3.73k/mm Figure 12 was taken under the conditions of directional solidification growth rate r=14.6μm/s and temperature gradient G _T = 3.73k/mm. It can be seen from Figure 11 that cell crystal growth is easy to bifurcate when there is no electric field. And the cell crystal spacing is relatively large; after the electric field is applied, the cell crystal growth has no bifurcation, and the cell crystal spacing is significantly reduced.

The present invention is committed to developing a device for applying an electric field to the growth of crystals in the process of directional solidification. With the help of existing scientific and technical personnel's discussions on the influence of the electric field on the behavior of the metal solid-liquid interface, to further reveal its impact on the metal directional solidification Solute distribution, temperature field distribution, and the mechanism of crystal growth.

Claims (7)

1. the device of a driving solidification and crystallization process by using electrical effect is characterized in that it comprises electric field generation systems (101), the thermostatted water circulatory system (102), crystallizer (103), CCD microscope (4), thermal resistance (5), communication instrument (7), serial communication interface (8), usb bus interface circuit (11) and computer (12);

The positive pole of described electric field generation systems (101) links to each other with the hot junction of crystallizer (103), the negative pole of electric field generation systems (101) links to each other with the cold junction of crystallizer (103), the thermostatted water circulatory system (102) is connected with crystallizer (103), guarantee crystallizer (103) temperature constant, CCD microscope (4) be arranged on crystallizer (103) directly over, and link to each other with the data communication end of computer (12) by usb bus interface circuit (11), thermal resistance (5) is preset in the crystallizer melting zone (30), and link to each other with the data input pin of communication instrument (7), the data output end of communication instrument (7) links to each other with the data communication end of computer (12) by serial communication interface (8).

2. the device of a kind of driving solidification and crystallization process by using electrical effect according to claim 1 is characterized in that described electric field generation systems (101) comprises sensitive galvanometer (1) and power supply (10);

The described thermostatted water circulatory system (102) comprises the melting zone cold junction thermostatted water circulatory system, the melting zone vertical electrode thermostatted water circulatory system and hot junction, the melting zone thermostatted water circulatory system;

Described crystallizer (103) comprises melting zone (30), hot junction, melting zone electrode plate (29), melting zone cold junction electrode plate (34), upper end vertical electrode (33), lower end vertical electrode (21), hot junction, melting zone heat transfer block (27), melting zone cold junction heat transfer block (36), vertical electrode upper end heat-transfer pipe (31), vertical electrode lower end heat-transfer pipe (20);

Described melting zone (30) is for having the rectangle carbonic ester piece of internal cavity structures, and described internal cavities is by a long and narrow space that end face retrained of an end face of upper and lower surface sheet glass, polycarbonate plate and melting zone cold junction electrode plate (34), hot junction electrode plate (29);

An end face of hot junction, melting zone heat transfer block (27) docks with an end face of hot junction, melting zone electrode plate (29), another end face of hot junction, melting zone electrode plate (29) has constituted an end face of melting zone (30), an end face of melting zone cold junction electrode plate (34) has constituted another end face of melting zone (30), another end face of melting zone cold junction electrode plate (34) docks with an end face of melting zone cold junction heat transfer block (36), in melting zone (30), place transparent class metalloid alloy on thermograde direction perpendicular to melting zone (30), and another side of (30) is provided with lower end vertical electrode (21) in the melting zone, vertical electrode upper end heat-transfer pipe (31) is arranged on the surface of upper end vertical electrode (33), and vertical electrode lower end heat-transfer pipe (20) is arranged on the surface of lower end vertical electrode (21);

The positive pole of the power supply (10) of described electric field generation systems (101) links to each other with hot junction, melting zone electrode plate (29), the negative pole of power supply (10) links to each other with melting zone cold junction electrode plate (34), and sensitive galvanometer (1) is connected in the circuit of power supply (10), hot junction, melting zone electrode plate (29) and melting zone cold junction electrode plate (34) composition;

Hot junction, the melting zone thermostatted water circulatory system is communicated with hot junction, the melting zone heat transfer block (27) of electric field generation systems (101), the melting zone cold junction thermostatted water circulatory system is communicated with the melting zone cold junction heat transfer block (36) of electric field generation systems (101), and the melting zone vertical electrode thermostatted water circulatory system is communicated with the upper end vertical electrode (33) and the lower end vertical electrode (21) of electric field generation systems (101).

3. the device of a kind of driving solidification and crystallization process by using electrical effect according to claim 2 is characterized in that hot junction, the melting zone thermostatted water circulatory system comprises the water-bath heating of hot junction, melting zone and temperature control module (23), hot junction, melting zone heat cycles water pump (24), two circulation pipes (25) and the heating water-bath (26) of hot junction, melting zone;

Hot junction, described melting zone heat transfer block (27) and melting zone cold junction heat transfer block (36) inside all have shape of a hoof UNICOM groove;

The temperature sense of water-bath heating of hot junction, described melting zone and temperature control module (23) partly is immersed in the heating of hot junction, melting zone with in the water-bath (26), circulation pipe (25) one ends insert the heating of hot junction, melting zone with in the water-bath (26), the other end of a circulation pipe (25) is communicated with an end of hot junction, melting zone heat transfer block (27) groove, another root circulation pipe (25) one ends insert the heating of hot junction, melting zone with in the water-bath (26) by hot junction, melting zone heat cycles water pump (24), the other end of another root circulation pipe (25) is communicated with the other end of hot junction, melting zone heat transfer block (27) groove, two circulation pipes (25) are formed a constant temperature circulatory system, keep the melting zone hot-side temperature constant;

The melting zone vertical electrode thermostatted water circulatory system comprises melting zone vertical electrode water-bath heating and temperature control module (18), melting zone vertical electrode heat cycles water pump (22), three circulation pipes (25) and melting zone vertical electrode heating water-bath (19);

The temperature sense of vertical electrode water-bath heating of described melting zone and temperature control module (18) partly is immersed in melting zone vertical electrode heating with in the water-bath (19), circulation pipe (25) one ends insert melting zone vertical electrode heating with in the water-bath (19), the other end of a circulation pipe (25) is connected with an end of vertical electrode lower end heat-transfer pipe (20), one end of another root circulation pipe (25) is connected with the other end of vertical electrode lower end heat-transfer pipe (20), the other end of another root circulation pipe (25) is connected with an end of vertical electrode upper end heat-transfer pipe (31), the 3rd circulation pipe (25) one ends insert melting zone vertical electrode heating with in the water-bath (19) by melting zone vertical electrode heat cycles water pump (22), the other end of the 3rd circulation pipe (25) is connected with the other end of vertical electrode upper end heat-transfer pipe (31), three circulation pipes (25) are formed a constant temperature circulatory system, keep melting zone vertical electrode temperature constant;

The melting zone cold junction thermostatted water circulatory system comprises cold junction water-bath temperature control instrument (17), melting zone cold junction water-cooled water circulating pump (15), two circulation pipes (25) and melting zone cold junction water bath with thermostatic control (16);

The temperature sense of described cold junction water-bath temperature control instrument (17) partly is immersed in the melting zone cold junction water bath with thermostatic control (16), circulation pipe (25) one ends insert in the melting zone cold junction water bath with thermostatic control (16), the other end of a circulation pipe (25) is communicated with an end of melting zone cold junction heat transfer block (36) groove, another root circulation pipe (25) one ends insert in the melting zone cold junction water bath with thermostatic control (16) by melting zone cold junction water-cooled water circulating pump (15), the other end of another root circulation pipe (25) is communicated with the other end of melting zone cold junction heat transfer block (36) groove, two circulation pipes (25) are formed a constant temperature circulatory system, keep the melting zone cold junction temperature constant.

4. the device of a kind of driving solidification and crystallization process by using electrical effect according to claim 3 is characterized in that circulation pipe (25) is the plastics circulation pipe.

5. according to the device of claim 2 or 3 described a kind of driving solidification and crystallization process by using electrical effect, it is characterized in that vertical electrode upper end heat-transfer pipe (31) and vertical electrode lower end heat-transfer pipe (20) are the red copper heat-transfer pipe, hot junction, melting zone heat transfer block (27) and melting zone cold junction heat transfer block (36) are the red copper heat transfer block.

6. the device of a kind of driving solidification and crystallization process by using electrical effect according to claim 3, it is characterized in that water-bath heating of hot junction, melting zone and temperature control module (23) be made up of hot junction heater (13-1) and hot junction water-bath temperature control instrument (14-1), the signal input part of described hot junction heater (13-1) links to each other with the signal output part of hot junction water-bath temperature control instrument (14);

Melting zone vertical electrode water-bath heating and temperature control module (18) are made up of vertical electrode heater (13-2) and vertical electrode water-bath temperature control instrument (14-2), and the signal input part of described vertical electrode heater (13-2) links to each other with the signal output part of vertical electrode water-bath temperature control instrument (14-2).

7. the device of a kind of driving solidification and crystallization process by using electrical effect according to claim 1 is characterized in that thermal resistance (5) is the film platinum resistance thermometer sensor.

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