阅读说明：本技术 一种利用固态相变制备定向TiAl基合金的装置及其制备方法 (Device for preparing oriented TiAl-based alloy by utilizing solid-state phase transition and preparation method thereof ) 是由 陈瑞润 方虹泽 刘阳力 王琪 丁鑫 王亮 苏彦庆 郭景杰 于 2021-09-23 设计创作，主要内容包括：一种利用固态相变制备定向TiAl基合金的装置及其制备方法,它涉及一种制备定向TiAl基合金的装置及其制备方法。本发明为了解决现有定向TiAl基合金制备过程中,试样表层易发生侧向散热,及工艺复杂的问题。本发明的液态Ga-In合金和热处理试棒位于真空室内的下部,调速器安在热处理试棒的底端,测温仪的导线端伸入真空室内并位于有效热处理区,感应线圈套装在热处理试棒的上部外侧。真空室内,将热处理试样置于感应线圈内；调节感应线圈与Ga-In合金液面的距离；感应线圈加热；抽真空并通氩气；对测量试样加热；当温度达到该TiAl基合金的β单相区温度范围内时,停止加热并保温；对TiAl基合金试棒进行定向热处理；冷却后,通入空气,取件。本发明用于制备定向TiAl基合金。(A device for preparing oriented TiAl-based alloy by utilizing solid phase transition and a preparation method thereof relate to a device for preparing oriented TiAl-based alloy and a preparation method thereof. The invention aims to solve the problems that in the existing preparation process of the directional TiAl-based alloy, the surface layer of a sample is easy to generate lateral heat dissipation, and the process is complex. The liquid Ga-In alloy and the heat treatment test bar are positioned at the lower part In the vacuum chamber, the speed regulator is arranged at the bottom end of the heat treatment test bar, the lead end of the temperature measuring instrument extends into the vacuum chamber and is positioned In an effective heat treatment area, and the induction coil is sleeved at the outer side of the upper part of the heat treatment test bar. Placing a heat treatment sample in an induction coil in a vacuum chamber; adjusting the distance between the induction coil and the Ga-In alloy liquid level; heating the induction coil; vacuumizing and introducing argon; heating a measurement sample; when the temperature reaches the temperature range of the beta single-phase region of the TiAl-based alloy, stopping heating and preserving heat; carrying out directional heat treatment on the TiAl-based alloy test bar; and (5) after cooling, introducing air, and taking the workpiece. The method is used for preparing the oriented TiAl-based alloy.)

1. An apparatus for producing an oriented TiAl-based alloy by solid-state phase transition comprises a vacuum chamber (1); the method is characterized in that: it also comprises a liquid Ga-In alloy (2), a speed regulator (3), an induction coil (4), a temperature measuring instrument (5), a heat treatment test bar (6) and an Ar gas cylinder (7),

the liquid Ga-In alloy (2) is positioned at the lower part In the vacuum chamber (1), the heat treatment test bar (6) is vertically arranged In the vacuum chamber (1), the speed regulator (3) is arranged at the bottom end of the heat treatment test bar (6) In a dovetail groove connection mode and regulates and controls the pull-down speed of the heat treatment test bar (6) In real time,

the wire end of the temperature measuring instrument (5) extends into the vacuum chamber (1) and is positioned in the effective heat treatment area (8), the induction coil (4) is sleeved on the outer side of the upper part of the heat treatment test bar (6) and heats the effective heat treatment area (8) on the heat treatment test bar (6), and the Ar gas cylinder (7) is connected with the vacuum chamber () 1.

2. The apparatus for preparing oriented TiAl-based alloy according to claim 1, wherein: the adjusting range of the speed regulator (3) is 0.01mm/min-1.0 mm/min.

3. A method for manufacturing an oriented TiAl-based alloy using a solid state phase transition according to any one of claims 1 to 2, characterized in that: it comprises the following steps:

firstly, placing a beta-solidified TiAl-based alloy heat treatment sample (6) In a five-turn induction coil (4) In a vacuum chamber (1), so that the axis of the heat treatment sample (6) is completely overlapped with the central line of the induction coil (4), and the bottom of the heat treatment sample (6) is placed In a liquid Ga-In alloy (2) and is connected with a drawing rod through a dovetail groove;

adjusting the distance between the induction coil (4) and the liquid level of the liquid Ga-In alloy (2) to ensure that an effective heat treatment area (8) of the heat treatment sample (6) is positioned In the effective heating range of the induction coil (4);

connecting the induction coil (4) with an electrode, wherein the frequency of alternating current is 50kHz, and the heating temperature is more than 1500 ℃;

step four, closing a door of the vacuum chamber (1), starting a vacuum pump, pumping the air pressure in the vacuum chamber (1) to be below 1Pa, then reversely filling high-purity argon into the vacuum chamber (1) to 300Pa, repeating the operation for 3-5 times, and finally ensuring that the directional heat treatment experiment is carried out under the protection of the argon gas with the pressure of less than 1 Pa;

step five, closing a power supply, and increasing the loading power of the induction coil (4) in a stepping manner, and simultaneously increasing the temperature of an effective heat treatment area (8) of the heat treatment test bar (6);

step six, when the temperature of the effective heat treatment area (8) reaches the temperature range of the beta single-phase area of the heat treatment test bar (6), stopping adjusting the loading power of the induction coil (4) and keeping the temperature for 5-20 min;

step seven, starting the drawing device, setting the directional drawing speed of the heat treatment test bar (6) to be 0.01mm/min-1.00mm/min through the speed regulator (3), and carrying out directional heat treatment on the heat treatment test bar;

and step eight, after the treatment is finished, reducing the loading power, introducing air into the vacuum chamber (1) after the test bar (6) to be subjected to heat treatment is cooled to room temperature, and taking out the test bar subjected to directional heat treatment to obtain the directionally arranged columnar crystal structure.

4. The method of claim 3, wherein the method comprises the following steps: the heat treatment test bar (6) in the first step is a TiAl-based alloy test sample, and the cross-sectional diameter size of the test bar is 15mm-25 mm.

5. The method for preparing an oriented TiAl-based alloy according to claim 4, wherein: the heat treatment bar (6) was placed In a pool of liquid Ga-18 at.% In alloy (2), the temperature of the liquid Ga-18 at.% In alloy (2) being constantly 25 ℃.

6. The method of claim 5, wherein the method comprises the following steps: the heating mode of the heat treatment test bar (6) in the third step is that the induction coil (4) is heated, the range of the effective heat treatment area (8) is 10mm-15mm in the vertical direction of the heat treatment test bar (6), the heating temperature is more than 1500 ℃, and the temperature of the effective heat treatment area (8) is ensured to be in the range of a beta single-phase area of the beta-solidified TiAl-based alloy in the directional heat treatment process.

7. The method of claim 6, wherein the method comprises the following steps: the induction coil (4) In the third step is made of red copper, the local heating temperature of the heat treatment test bar (6) reaches 1280-1690 ℃, and the cooling temperature of the liquid Ga-In alloy (2) to the heat treatment test bar (6) is 100-600 ℃.

8. The method of claim 7, wherein the method comprises the following steps: the size of the vacuum chamber (1) in the first step is 800mm, 700mm and 1200mm in length, width and height.

9. The method of claim 8, wherein the method comprises the following steps: the argon purity of the high-purity argon in the Ar gas cylinder (7) is 99.9999%.

Technical Field

The invention relates to a device and a method for preparing an oriented TiAl-based alloy, in particular to a device and a method for preparing an oriented TiAl-based alloy by utilizing solid-state phase transition, belonging to the technical field of material processing.

Background

TiAl-based alloy is known as the best material for replacing Ni-based high-temperature alloy at 600-900 ℃ due to the characteristics of small density, high specific strength, excellent high-temperature mechanical property and the like, and is expected to be applied to the preparation of aerospace turbine engine blades, so that the TiAl-based alloy is widely researched.

However, the alloy has the disadvantages of poor room temperature plasticity, easy oxidation of melt in the smelting process due to high chemical activity, coarse casting structure, serious component segregation and the like. The presence of these defects greatly limits the commercial production of this alloy. In order to optimize the microstructure of the TiAl-based alloy and improve the mechanical properties thereof, alloying methods and thermomechanical working methods are generally used. For TiAl-based alloy serving in a high-temperature environment, the directionally arranged columnar crystal or single crystal structure can greatly reduce the length of the transverse grain boundary of the alloy, thereby obviously improving the high-temperature mechanical property of the alloy.

Generally, the method for preparing the oriented TiAl-based alloy is mainly a directional solidification method. However, during directional solidification, the TiAl-based alloy melt inevitably comes into contact with the crucible or the coating material. For TiAl-based alloy melt with high chemical activity, the TiAl-based alloy melt is easy to chemically react with crucible materials or coating materials in the solidification process, so that the oriented growth of alloy chemical components and surface columnar crystals is influenced.

The invention discloses a directional annealing device and a method for preparing metal columnar crystals, which aim at preparing a TiAl-based alloy with a directionally arranged columnar crystal structure by using a heat treatment method, wherein the publication number is CN112048605A, and the name of the invention is 'a directional annealing device and a method for preparing metal columnar crystals', particularly discloses that Ti-48Al-2Nb-2Cr alloy with 70% of rolling deformation is directionally annealed to finally obtain the columnar crystal structure, but the method has the defects of complex process and high control precision because the TiAl alloy needs to be subjected to thermal deformation treatment, and the directional thermal treatment temperature of the subsequent alloy is between the recrystallization temperature and the melting point of the alloy, which is not explained.

In conclusion, in the existing preparation process of the directional TiAl-based alloy, because an alloy melt is in contact with a crucible wall or a coating material, the components of the directional TiAl-based alloy are influenced, and the lateral heat dissipation of the surface layer of a sample is easy to occur in the traditional directional solidification process, so that the problem of directional growth of columnar crystals on the surface layer is influenced, and meanwhile, the problem of complex process also exists.

Disclosure of Invention

The invention aims to solve the problems that in the existing preparation process of the directional TiAl-based alloy, because an alloy melt is contacted with a crucible wall or a coating material, the components of the directional TiAl-based alloy are influenced, and the directional growth of columnar crystals on the surface layer is influenced because the lateral heat dissipation is easy to occur on the surface layer of a sample in the traditional directional solidification process, and meanwhile, the process is complicated. Further provides a device for preparing the oriented TiAl-based alloy by utilizing solid-state phase transition and a preparation method thereof.

The technical scheme of the invention is as follows: a temperature measuring device in the directional solidification process of a cold crucible comprises a vacuum chamber; the device also comprises a liquid Ga-In alloy, a speed regulator, an induction coil, a temperature measuring instrument, a heat treatment test rod and an Ar gas cylinder, wherein the liquid Ga-In alloy is positioned at the lower part In the vacuum chamber, the heat treatment test rod is vertically arranged In the vacuum chamber, the speed regulator is arranged at the bottom end of the heat treatment test rod In a dovetail groove connection mode and regulates and controls the pull-down speed of the heat treatment test rod In real time, the wire end of the temperature measuring instrument extends into the vacuum chamber and is positioned In an effective heat treatment area, the induction coil is sleeved on the outer side of the upper part of the heat treatment test rod and heats the effective heat treatment area on the heat treatment test rod, and the Ar gas cylinder is connected with the vacuum chamber.

The invention also provides a method for preparing the oriented TiAl-based alloy by utilizing solid-state phase transition, which comprises the following steps:

placing a beta-solidified TiAl-based alloy heat treatment sample In a five-turn induction coil In a vacuum chamber, so that the axis of the heat treatment sample is completely overlapped with the central line of the induction coil, and the bottom of the heat treatment sample is placed In a liquid Ga-In alloy and connected with a drawing rod through a dovetail groove;

adjusting the distance between the induction coil and the liquid level of the liquid Ga-In alloy to ensure that an effective heat treatment area of the heat treatment sample is positioned In the effective heating range of the induction coil;

connecting the induction coil with an electrode, wherein the frequency of alternating current is 50kHz, and the heating temperature is more than 1500 ℃;

step four, closing a vacuum chamber door, starting a vacuum pump, pumping the air pressure in the vacuum chamber to be below 1Pa, then reversely filling high-purity argon into the vacuum chamber to 300Pa, repeating the operation for 3-5 times, and finally ensuring that the directional heat treatment experiment is carried out under the protection of the argon gas with the pressure of less than 1 Pa;

step five, closing a power supply, and increasing the loading power of the induction coil in a stepping manner, and simultaneously increasing the temperature of an effective heat treatment area of the heat treatment test bar;

step six, when the temperature of the effective heat treatment area reaches the temperature range of the beta single-phase area of the heat treatment test bar, stopping adjusting the loading power of the induction coil and keeping the temperature for 5-20 min;

step seven, starting the drawing device, setting the directional drawing speed of the heat treatment test bar to be 0.01mm/min-1.00mm/min through a speed regulator, and carrying out directional heat treatment on the heat treatment test bar;

and step eight, after the treatment is finished, reducing the loading power, introducing air into the vacuum chamber after the heat treatment test bar is cooled to room temperature, and taking out the test bar subjected to the directional heat treatment to obtain the directionally arranged columnar crystal structure.

Compared with the prior art, the invention has the following effects:

1. the invention can be suitable for common cast TiAl-based alloy without thermal deformation treatment, the tensile strength of the prepared Ti44Al6Nb1Cr alloy with oriented columnar crystal structure is 636MPa, the total strain is 2.28%, and the tensile strength is improved by 22% compared with the mechanical property of the alloy after directional solidification (523MPa, 3.03%).

2. The invention utilizes a heat treatment mode, leads beta crystal grains to grow directionally under the action of directional heat flow through solid-state phase transition, leads the transverse crystal boundary to migrate spontaneously, avoids the lateral heat dissipation of the surface layer of the sample, finally obtains the columnar crystal structure in directional arrangement, effectively avoids the TiAl-based alloy melt from contacting with a crucible or a coating material to influence the directional growth of alloy chemical components and crystal grains, and reduces the energy consumption.

3. After the directional heat treatment is adopted, as the temperature of the effective heat treatment area of the TiAl-based alloy test bar is ensured to be within the temperature range of a beta single-phase area in the sixth step and the seventh step, and the proper drawing rate is set at the same time, the grain directional growth can be ensured, therefore, the directional arrangement of columnar crystal structures is obtained, the lamellar clusters are changed into columns from ellipsoids, the B2 phase is changed into strips from meshes, the directionality of the microstructure of the TiAl-based alloy is obviously improved, and the specific performance improvement is shown as follows: the lamellar clusters in the alloy microstructure are changed into columnar shape after the directional heat treatment from the original ellipsoid shape, the B2 phase is changed into strip shape from net shape, compared with the common cast alloy, the tensile strength of the alloy after the directional heat treatment is greatly improved, and the total strain is also improved, namely the performance in the table 1.

4. Compared with the directionally solidified Ti44Al6Nb1Cr alloy, the tensile strength of the alloy after the directional heat treatment reaches 636MPa, and the total strain is 2.28%. Compared with the Ti44Al6Nb1Cr alloy prepared by directional solidification, the tensile strength is improved by 22 percent.

Drawings

FIG. 1 is a schematic view of a directional heat treatment device for a beta-solidified TiAl-based alloy, which is used for obtaining a directionally arranged columnar crystal structure by adjusting the loading power of an induction coil, the distance between the induction coil and a Ga-In liquid alloy, the movement rate of a drawing rod, and controlling the temperature, the directional heat flow, the temperature gradient and the interface continuous migration of an effective heat treatment area of a test bar.

FIG. 2 is a macroscopic structure view of the Ti44Al6Nb1Cr alloy of the example before and after directional heat treatment in (a) an as-cast state, (b) a directionally solidified state, and (c) a directionally heat treated state.

FIG. 3 is a microstructure of the Ti44Al6Nb1Cr alloy of the examples before and after the directional heat treatment, wherein (a) is in an as-cast state, (b) is in a directionally solidified state, and (c) is in a directionally heat-treated state.

Detailed Description

The first embodiment is as follows: the present embodiment will be described with reference to fig. 1, and an apparatus for producing an oriented TiAl-based alloy using solid-state phase transition according to the present embodiment includes a vacuum chamber 1; the device also comprises a liquid Ga-In alloy 2, a speed regulator 3, an induction coil 4, a thermodetector 5, a heat treatment test rod 6 and an Ar gas cylinder 7, wherein the liquid Ga-In alloy 2 is positioned at the lower part In the vacuum chamber 1, the heat treatment test rod 6 is vertically arranged In the vacuum chamber 1, the speed regulator 3 is arranged at the bottom end of the heat treatment test rod 6 In a dovetail groove connection mode and regulates and controls the pull-down speed of the heat treatment test rod 6 In real time, the wire end of the thermodetector 5 extends into the vacuum chamber 1 and is positioned In an effective heat treatment area 8, wherein a wire of the thermodetector is separately led out from the furnace, and an external power supply is constant-pressure 220V; the induction coil is provided with an independent power supply, the power supply is 380V, the induction coil 4 is sleeved on the outer side of the upper part of the heat treatment test bar 6 and heats an effective heat treatment area 8 on the heat treatment test bar 6, and the Ar gas cylinder 7 is connected with the vacuum chamber 1.

The heat treatment test bar 6 and the speed regulator 3 are connected in a dovetail groove mode, the speed regulator can be guaranteed to regulate and control the lower drawing speed of the heat treatment test bar 6 in real time, and the regulating range of the speed regulator 3 is 0.01mm/min-1.0 mm/min.

The second embodiment is as follows: the present embodiment will be described with reference to fig. 1, and the adjustment range of the speed governor 3 of the present embodiment is 0.01mm/min to 1.0 mm/min. So set up, adjust the precision height. Other components and connections are the same as in the first embodiment.

The heat treatment test bar 6 and the speed regulator 3 are connected in a dovetail groove mode, so that the speed regulator can regulate and control the lower drawing speed of the heat treatment test bar 6 in real time, and the regulating range of the speed regulator 3 is 0.01mm/min-1.0 mm/min; the induction coil 4 is made of red copper, the heat treatment test bar 6 can be heated to 1280-1690 ℃ locally, the liquid Ga-In alloy 2 can cool the heat treatment test bar 6 to 100-600 ℃, and thus the heat treatment test bar 6 can be ensured to form the required temperature gradient; the temperature measuring instrument 5 can monitor the temperature change of the heat treatment test bar 6 heated by the induction coil 4 in real time, and the temperature measuring precision is +/-10 ℃; the length, the width and the height of the vacuum chamber 1 are 800mm, 700mm and 1200mm, so that the TiAl alloy directional preparation method can be realized; the purity of the argon in the Ar gas bottle 7 is 99.9999 percent, the oxygen content in the vacuum chamber 1 can be ensured to be lower, and the whole preparation process is carried out under the protection of inert gas argon.

The third concrete implementation mode: the present embodiment will be described with reference to fig. 1, and the method for preparing an oriented TiAl-based alloy by solid-state phase transition according to the present embodiment includes the steps of:

step one, In a vacuum chamber 1, placing a beta-solidified TiAl-based alloy heat treatment sample 6 In a five-turn induction coil 4, so that the axis of the heat treatment sample 6 is completely overlapped with the central line of the induction coil 4, and the bottom of the heat treatment sample 6 is placed In a liquid Ga-In alloy 2 and connected with a drawing rod through a dovetail groove;

step two, adjusting the distance between the induction coil 4 and the liquid level of the liquid Ga-In alloy 2 to ensure that an effective heat treatment area 8 of the heat treatment sample 6 is positioned In the effective heating range of the induction coil 4;

connecting the induction coil 4 with an electrode, wherein the frequency of alternating current is 50kHz, and the heating temperature is more than 1500 ℃;

step four, closing a door of the vacuum chamber 1, starting a vacuum pump, pumping the air pressure in the vacuum chamber 1 to be below 1Pa, then reversely filling high-purity argon into the vacuum chamber 1 to 300Pa, repeating the operation for 3-5 times, and finally ensuring that the directional heat treatment experiment is carried out under the protection of the argon gas with the pressure of less than 1 Pa;

step five, closing a power supply, and increasing the loading power of the induction coil 4 in a stepping manner, and simultaneously increasing the temperature of the effective heat treatment area 8 of the heat treatment test bar 6;

step six, when the temperature of the effective heat treatment area 8 reaches the temperature range of the beta single-phase area of the heat treatment test bar 6, stopping adjusting the loading power of the induction coil 4 and keeping the temperature for 5-20 min;

step seven, starting the drawing device, setting the directional drawing speed of the heat treatment test bar 6 to be 0.01mm/min-1.00mm/min through the speed regulator 3, and carrying out directional heat treatment on the heat treatment test bar;

and step eight, after the treatment is finished, reducing the loading power, introducing air into the vacuum chamber 1 after the heat-treated test bar 6 is cooled to room temperature, and taking out the test bar subjected to the directional heat treatment to obtain the directionally arranged columnar crystal structure.

The temperature measuring instrument 5 of the present embodiment can monitor the temperature change of the heat treatment test bar 6 heated by the induction coil 4 in real time, and the temperature measuring precision is ± 10 ℃.

The fourth concrete implementation mode: the present embodiment will be described with reference to FIG. 1. the heat-treated test bar 6 in the first step of the present embodiment is a TiAl-based alloy sample, preferably a Ti44Al6Nb1Cr alloy, having a cross-sectional diameter of 15mm to 25mm, preferably 20 mm. Other compositions and connection relationships are the same as in the first, second or third embodiment.

The fifth concrete implementation mode: referring to fig. 1, the heat treatment bar 6 of the present embodiment is placed In a pool of the liquid Ga-18 at.% In alloy 2, and the temperature of the liquid Ga-18 at.% In alloy 2 is constantly set to 25 ℃. This ensures that the test bar 6 is subjected to downward heat conduction during the directional heat treatment. Other compositions and connection relationships are the same as those in the first, second, third or fourth embodiment.

The sixth specific implementation mode: referring to FIG. 1, the heat treatment test bar 6 in the third step of the present embodiment is heated by the induction coil 4, the effective heat treatment zone 8 is within the range of 10mm-15mm in the vertical direction of the heat treatment test bar 6, and the heating temperature can reach 1500 ℃ or higher, so that the temperature of the effective heat treatment zone 8 is within the range of the beta single-phase zone of the beta-solidified TiAl-based alloy during the directional heat treatment. By the arrangement, grains in the effective heat treatment area of the test bar grow spontaneously, and grain boundaries continuously migrate under the action of directional heat flow. Other compositions and connection relations are the same as those of the first, second, third, fourth or fifth embodiment modes.

The seventh embodiment: referring to FIG. 1, the present embodiment will be described, wherein the induction coil 4 In the third step of the present embodiment is a red copper material, the temperature of locally heating the heat-treated test bar 6 is 1280 to 1690 ℃, and the temperature of cooling the heat-treated test bar 6 with the liquid Ga-In alloy 2 is 100 to 600 ℃. So set up, can guarantee that heat treatment test bar 6 forms required temperature gradient. Other compositions and connection relationships are the same as in the first, second, third, fourth, fifth or sixth embodiment.

The specific implementation mode is eight: the present embodiment will be described with reference to fig. 1, and the dimension length × width × height of the vacuum chamber 1 in the first step of the present embodiment is 800mm × 700mm × 1200 mm. By the arrangement, the method for directionally preparing the TiAl alloy can be realized. Other compositions and connection relationships are the same as in the first, second, third, fourth, fifth or sixth embodiment.

The specific implementation method nine: in the present embodiment, the argon purity of the high-purity argon gas in the Ar gas cylinder 7 of the present embodiment is 99.9999% as described with reference to fig. 1. By such arrangement, the oxygen content in the vacuum chamber 1 can be ensured to be lower, and the whole preparation process is carried out under the protection of inert gas argon. Other compositions and connections are the same as for embodiments one, two, three, four, five or six.

Example (b):

the invention relates to a device for preparing oriented TiAl-based alloy by utilizing solid phase transition, which structurally comprises a vacuum chamber 1, a liquid Ga-In alloy 2, a speed regulator 3, an induction coil 4, a temperature measuring instrument 5, a heat treatment test rod 6, an Ar gas cylinder 7 and an effective heat treatment area 8; the heat treatment test bar 6 is connected with the speed regulator 3 in a dovetail groove mode, the speed regulator can regulate and control the lower drawing speed of the heat treatment test bar 6 in real time, and the regulating range of the speed regulator 3 is 0.01mm/min-1.0 mm/min; the induction coil 4 is made of red copper, the heat treatment test bar 6 can be heated to 1280-1690 ℃ locally, the liquid Ga-In alloy 2 can cool the heat treatment test bar 6 to 100-600 ℃, and thus the heat treatment test bar 6 can be ensured to form the required temperature gradient; the temperature detector 5 can monitor the temperature change of the heat treatment test bar 6 heated by the induction coil 4 in real time, and the temperature measurement precision is +/-10 ℃; the length, the width and the height of the vacuum chamber 1 are 800mm, 700mm and 1200mm, so that the method for directionally preparing the TiAl alloy can be realized; the purity of argon in the Ar gas bottle 7 is 99.9999 percent, the oxygen content in the vacuum chamber 1 can be ensured to be lower, and the whole preparation process is carried out under the protection of inert gas argon.

The invention relates to a preparation method for preparing oriented TiAl-based alloy by utilizing solid-state phase transition, which comprises the following process steps:

step one, In a vacuum chamber 1, placing a beta-solidified TiAl-based alloy heat treatment sample 6 In a five-turn induction coil 4, so that the axis of the treatment sample 6 is completely overlapped with the central line of the induction coil 4, and the bottom of the treatment sample 6 is placed In a liquid Ga-In alloy 2 and connected with a drawing rod through a dovetail groove;

step two, adjusting the distance between the induction coil 4 and the liquid level of the Ga-In alloy 2 to ensure that the effective heat treatment area of the heat treatment sample 6 is positioned In the effective heating range of the induction coil 4;

connecting the induction coil 4 with an electrode, wherein the frequency of alternating current is 50kHz, the range of the effective heating treatment area 8 for heating is 10-15 mm, and the heating temperature can reach more than 1500 ℃;

step four, closing a door 1 of the vacuum chamber, starting a vacuum pump, pumping the air pressure in the vacuum chamber to be below 1Pa, then reversely filling high-purity argon gas into the vacuum chamber for 7-300 Pa, repeating the operation for 3-5 times, and finally ensuring that the directional heat treatment experiment is carried out under the protection of the argon gas with the pressure of less than 1 Pa;

step five, closing a power supply, increasing the loading power of the induction coil 4 in a stepping mode, and measuring the temperature of an effective heating area of the sample 6;

step six, when the temperature of the effective heat treatment area of the sample reaches the temperature range of the beta single-phase area of the TiAl-based alloy 6, stopping adjusting the loading power of the induction coil 4 and keeping the temperature for 5-20 min;

step seven, starting the drawing device, setting the directional drawing speed of the test bar to be 0.01mm/min-1.00mm/min, preferably 0.25mm/min through the speed regulator 3, and carrying out directional heat treatment on the TiAl-based alloy test bar 6;

and step eight, after the treatment is finished, quickly reducing the loading power, introducing air into the vacuum chamber 1 after the test bar 6 is cooled to room temperature, and taking out the test bar 6 subjected to the directional heat treatment to obtain the directionally arranged columnar crystal structure.

The macroscopic structure is shown in figure 2, the as-cast TiAl alloy is in the shape of equiaxed crystals as shown in figure 2a, the directionally solidified microstructure shown in figure 2b has columnar crystals but has poor directional effect and discontinuous columnar crystal growth, and figure 2c is the large-size continuously grown columnar crystal microstructure obtained by the invention patent, and the columnar crystals which are obviously directionally arranged can be seen. The microstructure is shown in fig. 3, the orientation of the microstructure of the Ti44Al6Nb1Cr alloy is obviously improved, and the microstructure under the back scattering condition of fig. 3 shows that the growth direction of the tissue lamellar cluster obtained by the invention patent is basically parallel to the direction of the temperature gradient, and the orientation of the lamellar cluster is consistent. The room temperature tensile property of the alloy is shown in table 1, and the mechanical property of the alloy obtained by the preparation method and the device for preparing the oriented TiAl-based alloy by utilizing solid-state phase transition is greatly improved, the room temperature tensile strength of the oriented TiAl-based alloy obtained by the invention is 636MPa, the total strain is 2.28 percent, and the tensile strength is improved by 22 percent compared with the mechanical property of the alloy after oriented solidification (523MPa,3.03 percent).

TABLE 1 mechanical Properties of Ti44Al6Nb1Cr alloy in different states