CN113981273B - Multi-orientation lamellar structure TiAl alloy with initial solidification phase as alpha phase and preparation method and application thereof - Google Patents
Multi-orientation lamellar structure TiAl alloy with initial solidification phase as alpha phase and preparation method and application thereof Download PDFInfo
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Abstract
The invention belongs to the technical field of titanium alloy lamellar control, and particularly relates to a multi-orientation lamellar structure TiAl alloy with an initial solidification phase of an alpha phase, and a preparation method and application thereof. The preparation method provided by the invention comprises the following steps: heating the local part of the TiAl alloy base material by using a heating device, heating the temperature of the TiAl alloy base material in an effective hot zone to the temperature of an alpha phase zone for heat preservation treatment, then sequentially carrying out local heat treatment and temperature-controlled cooling, wherein the cooling rate of the temperature-controlled cooling is more than or equal to 5 ℃/s, and the obtained TiAl has a multi-orientation gamma phase lamellar layer and a multi-orientation alpha phase lamellar layer2The TiAl alloy with the multi-orientation lamellar structure is prepared without melting the structure formed by the photo layer.
Description
Technical Field
The invention belongs to the technical field of titanium alloy lamellar control, and particularly relates to a multi-orientation lamellar structure TiAl alloy with an initial solidification phase of an alpha phase, and a preparation method and application thereof.
Background
The development process and the technical means of TiAl alloy directional solidification are systematically summarized in the aerospace material directional solidification written in the scientific published society technical work by the Fu constant Zhi et al in 2015, and the transverse grain boundary is eliminated through the control of the melting and solidification processes. When the solidification primary phase is an alpha phase, the phase change path from high temperature to low temperature of the TiAl alloy is as follows: l (liquid phase) → L + α → α → α + γ/α (high temperature sheet layer) → γ/α2(ordered sheet). At the moment, the gamma/alpha is finally generated under the influence of the preferred alpha solidification orientation and the solid phase transition crystallographic orientation relation2The lamellae were oriented at 90 deg. to the growth direction (perpendicular to the growth direction). Inui et Al prepared single crystals of alpha-solidifying TiAl alloys for the first time, having a single lamellar orientation with a composition of Ti-49.3Al (at.%), and related results were published in "Room-temperature tensile deformation of synthetic twisted (PST) crystals of TiAl. acta Metallurgica et materials.1992, 40(11): 3095-. For Ti-48Al(at.%) alpha solidification oriented alloy, work by G.Wegmann and H.Y.Kim et al, which showed excellent creep performance at 853 ℃, are published in the "formation characteristics of synthetic thermoplastic steel sheet at 1150 K.Intermetals.2000, 8: 165-177" and "Parallel casting steel sheet formation in soft orientation PST crystal of TiAl alloy 2001,49: 2635-2643", respectively.
Controlling the orientation of the alpha-solidified TiAl alloy oriented tissue lamella: chinese patent CN104328501A discloses a TiAl single crystal with fully controllable lamellar orientation and a preparation method thereof, aiming at alpha solidification characteristic Ti-49Al-9Nb (at.%) alloy, based on the preparation of a water-cooled copper crucible master alloy ingot and the directional solidification of a yttria coating high-purity corundum tube, and the final lamellar orientation is parallel to the growth direction through solidification and solid phase change control. Chinese patent CN104651650A discloses a method for preparing TiAl-based alloy oriented fully-lamellar structure, which adopts a seed remelting and oriented solidification method to carry out lamellar orientation control on Ti-48Al-2Cr-2Nb (at.%) alloy with alpha solidification characteristics, and the final lamellar orientation is parallel to the growth direction. Chinese patent CN105821470A discloses a dual-structure TiAl alloy and a preparation method thereof, and a unidirectional solidification means after smelting is adopted to prepare a single-orientation columnar crystal and an equiaxed crystal structure of the TiAl alloy with alpha solidification characteristics.
In the report of the alpha-solidified TiAl alloy oriented structure lamellar orientation control method, the lamellar orientation is controlled singly, the condition that the lamellar orientation is parallel to the growth direction is emphasized too much, and the performance advantages of other lamellar orientations are ignored.
Disclosure of Invention
In view of the above, the invention provides a multi-orientation lamellar structure TiAl alloy with an initial solidification phase of an alpha phase, and a preparation method and application thereof.
In order to achieve the above object, the present invention provides the following technical solutions:
the invention provides a preparation method of alloy multi-orientation lamellar structure TiAl with an initial solidification phase of alpha phase, which comprises the following steps:
heating a local part of a TiAl alloy base material by using a heating device, heating the temperature of the TiAl alloy base material in an effective hot zone to the temperature of an alpha phase zone, and carrying out heat preservation treatment to obtain a TiAl alloy heat preservation thermal part with a temperature gradient, wherein the TiAl alloy base material is an alpha phase solidified TiAl alloy;
the TiAl alloy heat-preservation hot piece and the heating device move relatively to carry out local heat treatment on the TiAl alloy heat-preservation hot piece to obtain a heat-treated alpha-phase TiAl alloy hot piece;
and carrying out temperature control cooling on the heat-treated alpha-phase TiAl alloy hot piece, wherein in the process of temperature control cooling, the TiAl alloy is changed into a multi-oriented gamma phase and a multi-oriented alpha phase from an alpha phase2Photographic layer structure, the termination temperature of the temperature-controlled cooling is lower than the alpha phase alpha of the TiAl alloy2The phase transition temperature of the phase, and the cooling rate of the temperature-controlled cooling is less than or equal to 15 ℃/s.
Preferably, the volume ratio of the TiAl alloy base metal positioned in the effective hot zone to the TiAl alloy base metal is (4-10): 100.
Preferably, when the local part of the TiAl alloy base material is heated, the temperature of the alpha phase region is 1370-1480 ℃.
Preferably, the temperature raising process for raising the temperature from room temperature to the temperature in the α -phase region when locally heating the TiAl alloy base material is: raising the temperature from room temperature to a first temperature according to a first temperature raising rate, and raising the temperature from the first temperature to the temperature of the alpha phase region according to a second temperature raising rate; the first temperature rise rate is 10-30 ℃/s, the second temperature rise rate is 2-5 ℃/s, and the first temperature is 1150-1250 ℃.
Preferably, the time of the heat preservation treatment is 5-15 min, the temperature of the TiAl alloy base metal in the effective hot zone during the heat preservation treatment is alpha phase zone temperature, and the alpha phase zone temperature is 1370-1480 ℃.
Preferably, the relative speed of the relative motion is 2-10 μm/s.
Preferably, during the local heat treatment, the volume ratio of the TiAl alloy base metal in the effective hot zone to the TiAl alloy base metal is (4-10): 100, the temperature of the TiAl alloy base metal in the effective hot zone is alpha phase zone temperature, and the alpha phase zone temperature is 1370-1480 ℃.
Preferably, the termination temperature of the temperature-controlled cooling is less than or equal to 800 ℃.
The invention provides the multi-orientation lamellar structure TiAl alloy with the initial solidification phase of alpha phase obtained by the preparation method in the technical scheme, the atomic percent of Al element of the multi-orientation lamellar structure TiAl alloy is more than or equal to 47.5 at.%, and the multi-orientation lamellar structure is multi-orientation gamma phase and alpha phase2The volume percentage of the gamma-ray film structure is more than or equal to 90 percent.
The invention provides application of the multi-orientation lamellar structure TiAl alloy with the initial solidification phase of the alpha phase in aerospace.
The invention provides a preparation method of a multi-orientation lamellar structure TiAl alloy with an initial solidification phase of an alpha phase, which comprises the following steps: heating a local part of a TiAl alloy base material by using a heating device, heating the temperature of the TiAl alloy base material in an effective hot area to the temperature of an alpha phase area to obtain a TiAl alloy hot piece with a temperature gradient, and carrying out heat preservation treatment on the TiAl alloy hot piece to obtain a TiAl alloy heat preservation hot piece with the temperature gradient, wherein the TiAl alloy base material is an alpha-phase solidified TiAl alloy; the TiAl alloy heat-preservation hot piece and the heating device move relatively to carry out local heat treatment on the TiAl alloy heat-preservation hot piece to obtain a heat-treated alpha-phase TiAl alloy hot piece; and carrying out temperature control cooling on the heat-treated alpha-phase TiAl alloy hot piece, wherein during the temperature control cooling, the TiAl alloy is changed into a multi-oriented gamma phase and a multi-oriented alpha phase from an alpha phase2Photo layer structure, the termination temperature of the temperature-controlled cooling is lower than the alpha phase alpha of TiAl alloy2The phase transition temperature of the phase, and the cooling rate of the temperature-controlled cooling is less than or equal to 15 ℃/s. According to the invention, the TiAl alloy base metal with alpha-phase solidification characteristic is locally heated until the temperature of the TiAl alloy base metal in the effective hot zone is the alpha-phase zone temperature, so that the element atoms in the TiAl alloy base metal in the effective hot zone have high migration rate, and meanwhile, the heat preservation treatment is carried out on the obtained TiAl alloy hot piece with temperature gradient, so that the primitiveness of the TiAl alloy hot piece can be effectively reducedChemical composition segregation and uniform temperature distribution of the TiAl alloy base metal in the effective hot zone are ensured; then, when the local heat treatment is carried out on the TiAl alloy heat-insulating hot piece with the temperature gradient, under the combined action of the temperature gradient, the orientation difference of adjacent crystal grains and the curvature of the crystal boundary, the crystal boundary of the original crystal phase of the TiAl alloy base material is transferred into columnar distribution from axial distribution along with relative motion, and after competitive growth elimination, the isometric crystal structure of the original crystal phase gradually evolves into an alpha-phase columnar crystal structure and presents a state of coexistence of multiple orientations; finally, the invention reduces the cooling rate to be less than or equal to 15 ℃/s through temperature control cooling until the termination temperature is lower than the alpha phase alpha of TiAl alloy2In the phase transition temperature process of the phases, when the temperature is reduced to an alpha + gamma two-phase region, a gamma phase sheet layer is separated out from a high-temperature alpha mother phase, and because the high-temperature alpha mother phase has a multi-orientation characteristic, the formed gamma/alpha high-temperature two-phase sheet layer tissue is influenced by the solid phase transition phase relation and tissue inheritance, and also has the multi-orientation characteristic, and as the temperature is continuously reduced, the gamma photo layer is continuously separated out; when the temperature is reduced to be lower than the alpha phase alpha of the TiAl alloy2At the phase transition temperature of the phase, the high-temperature alpha phase is orderly converted into alpha2Phase to finally form multi-oriented gamma/alpha2The lamellar structure and the state of the oriented columnar crystal are maintained.
The method provided by the invention has no melting and solidification processes, can obtain the multi-orientation lamellar organized TiAl alloy under the solid phase, is simple to operate and is suitable for industrial production.
Drawings
FIG. 1 is an electron micrograph of an as-cast structure of a raw material in example 1 of the present invention;
FIG. 2 is an electron micrograph of an as-cast structure of a product according to example 1 of the present invention;
FIG. 3 is a comparison of the mechanical property test results of the raw material and the product of example 1 of the present invention;
FIG. 4 is an electron micrograph of an as-cast structure of a raw material in example 2 of the present invention;
FIG. 5 is an electron micrograph of an as-cast structure of a product obtained in example 2 of the present invention;
FIG. 6 is a comparison of the mechanical property test results of the raw materials and the products of example 2 of the present invention;
FIG. 7 is a schematic view of a multi-oriented lamellar oriented tissue and a lamellar oriented tissue parallel to the growth direction prepared by the method provided by the invention.
Detailed Description
The invention provides a preparation method of a multi-orientation lamellar structure TiAl alloy with an initial solidification phase of an alpha phase, which comprises the following steps:
heating a local part of a TiAl alloy base material by using a heating device, heating the temperature of the TiAl alloy base material in an effective hot area to the temperature of an alpha phase area to obtain a TiAl alloy hot piece with a temperature gradient, and carrying out heat preservation treatment on the TiAl alloy hot piece to obtain a TiAl alloy heat preservation hot piece with the temperature gradient, wherein the TiAl alloy base material is an alpha-phase solidified TiAl alloy;
the TiAl alloy heat-preservation hot piece and the heating device move relatively to carry out local heat treatment on the TiAl alloy heat-preservation hot piece to obtain a heat-treated alpha-phase TiAl alloy hot piece;
and carrying out temperature control cooling on the heat-treated alpha-phase TiAl alloy hot piece, wherein during the temperature control cooling, the TiAl alloy is changed into a multi-oriented gamma phase and a multi-oriented alpha phase from an alpha phase2Photo layer structure, the termination temperature of the temperature-controlled cooling is lower than the alpha phase alpha of TiAl alloy2The phase transition temperature of the phase, and the cooling rate of the temperature-controlled cooling is less than or equal to 15 ℃/s.
The method uses a heating device to heat the local part of the TiAl alloy base metal, and heats the temperature of the TiAl alloy base metal in an effective hot zone to the temperature of an alpha phase zone to obtain the TiAl alloy hot piece with a temperature gradient.
In the present invention, the TiAl alloy base material is an α -phase solidified TiAl alloy, that is, the primary phase of the TiAl alloy base material is an α -phase. In the present invention, the atomic percentage of the Al element in the TiAl alloy base material is preferably not less than 47.5 at.%, and more preferably 47.5 to 49.8 at.%. In a specific embodiment of the present invention, the TiAl alloy base material is Ti-48% Al (at.%) or Ti-48Al-2Cr-2Nb (at.%). In a specific implementation of the invention, the TiAl alloy base material is of an isometric crystal structure, the primary phase of the TiAl alloy base material is an alpha phase, the TiAl alloy base material is rod-shaped, and the length of the TiAl alloy base material is 30-100 mm.
In the specific implementation of the invention, the heating device is preferably an induction heating coil, and the width of the thermal effect zone of the heating device is preferably less than or equal to 6 mm. The TiAl alloy base metal is locally heated by a heating device.
In the present invention, the heating is preferably performed in a directional heat treatment furnace.
In the present invention, when locally heating the TiAl alloy base material, the heating atmosphere is preferably an inert gas atmosphere, more preferably an Ar gas atmosphere; the pressure of the heating atmosphere is preferably 250-550 Pa, and more preferably 500 Pa. In a particular embodiment of the invention, the heated atmosphere is preferably obtained by: and vacuumizing the heating area, and then introducing inert gas. In the present invention, the evacuation is performed to a degree of vacuum of preferably 1 × 10-3～5×10-3Pa, more preferably 2X 10-3～3×10-3Pa; the inert gas is introduced until the pressure of the heated atmosphere is preferably 250-550 Pa, and more preferably 300-500 Pa; the operation of introducing the inert gas after vacuumizing is preferably repeated for 3-5 times.
In the present invention, when locally heating the TiAl alloy base material, the volume ratio of the TiAl alloy base material located in the effective hot zone to the TiAl alloy base material is preferably (4-10): 100, and more preferably (6-8): 100.
In the invention, when the local part of the TiAl alloy base material is heated, the temperature of the TiAl alloy base material in the effective hot zone is the temperature of an alpha phase zone, and in the invention, when the temperature of the TiAl alloy is the temperature of the alpha phase zone, the TiAl alloy is in an alpha single-phase state; in the invention, the temperature of the alpha phase region is preferably 1370-1480 ℃, and more preferably 1400-1450 ℃.
In the present invention, when locally heating the TiAl alloy base material, the temperature raising process from room temperature to the α -phase zone temperature is preferably: heating from room temperature to a first temperature at a first heating speed, and heating from the first temperature to the alpha-phase region temperature at a second heating speed; the first heating rate is preferably 10-30 ℃/s, and more preferably 15-25 ℃/s; the second heating rate is preferably 2-5 ℃/s, and more preferably 2.5-4 ℃/s; the first temperature is preferably 1150-1250 ℃, and more preferably 1200 ℃.
When the temperature is increased from room temperature to the first temperature, the storage energy release caused by long-time heating of the TiAl alloy can be effectively avoided by adopting the first temperature-increasing rate; when the temperature is increased from the second temperature to the temperature of the alpha phase region, the TiAl alloy can be further prevented from melting by adopting the second temperature increasing rate.
After the TiAl alloy hot piece with the temperature gradient is obtained, the invention carries out heat preservation treatment on the TiAl alloy hot piece to obtain the TiAl alloy heat preservation hot piece with the temperature gradient.
In the invention, the time of the heat preservation treatment is preferably 5-15 min, and more preferably 6-12 min; the temperature of the TiAl alloy base metal in the effective hot zone during heat preservation treatment is preferably alpha phase zone temperature, and the alpha phase zone temperature is preferably 1370-1480 ℃, and more preferably 1400-1450 ℃.
The heat preservation treatment can effectively reduce the chemical composition segregation of the original structure of the TiAl alloy and ensure that the temperature distribution of the TiAl alloy base metal in the effective hot zone is uniform.
The invention carries out heat preservation treatment on the TiAl alloy hot piece with the temperature gradient by the heat device.
After the TiAl alloy heat-preservation thermal piece with the temperature gradient is obtained, the TiAl alloy heat-preservation thermal piece and a heating device are moved relatively, and the TiAl alloy heat-preservation thermal piece is subjected to local heat treatment to obtain a heat-treated alpha-phase TiAl alloy thermal piece.
In the invention, during the local heat treatment, the volume ratio of the TiAl alloy base metal positioned in the effective hot zone to the TiAl alloy base metal is preferably (4-10): 100, and more preferably (6-8): 100; the temperature of the TiAl alloy base material in the effective hot zone is preferably alpha phase zone temperature, and the alpha phase zone temperature is preferably 1370-1480 ℃, and more preferably 1400-1450 ℃.
The invention realizes the relative movement of the TiAl alloy heat-insulating thermal piece and the heating device by fixing the TiAl alloy by moving the heating device, fixing the heating device by moving the TiAl alloy or simultaneously moving the TiAl alloy and the heating device.
In the invention, the relative speed of the relative movement is preferably 2-10 μm/s, and more preferably 3-8 μm/s. In the specific embodiment of the invention, when the relative motion is carried out, the heating device is fixed, the TiAl alloy is moved by moving the loading device of the TiAl alloy, and the heating device and the TiAl alloy are enabled to carry out the relative motion.
The invention can further ensure that the temperature of the TiAl alloy base metal in the effective hot zone is the temperature of the alpha phase zone by controlling the relative speed of the relative motion, and realize the uniform temperature of the TiAl alloy base metal in the effective hot zone.
When the local heat treatment is carried out on the TiAl alloy heat-insulating hot piece with the temperature gradient, under the combined action of the temperature gradient, the phase difference of adjacent crystal grains and the curvature of the crystal grain boundary, the crystal grain boundary of the original crystal phase of the TiAl alloy base material is relatively moved from axial distribution to columnar distribution, and after competitive growth elimination, the isometric crystal structure of the original crystal phase gradually evolves into an alpha-phase columnar crystal structure and presents a state of coexistence of multiple orientations.
The invention transforms the TiAl alloy base material into alpha-phase TiAl alloy through local heat treatment.
In the present invention, the TiAl alloy base material is always in a solid state during the local heat treatment.
After the heat-treated alpha-phase TiAl alloy hot piece is obtained, the heat-treated alpha-phase TiAl alloy hot piece is subjected to temperature control cooling, and during the temperature control cooling, the TiAl alloy is changed into a multi-oriented gamma phase and a multi-oriented alpha phase from an alpha phase2Photo layer structure, the termination temperature of the temperature-controlled cooling is lower than the alpha phase alpha of TiAl alloy2Phase transition temperature of the phase.
The heating device is stopped to heat the TiAl alloy after the relative movement is stopped, and then the heat treatment alpha-phase TiAl alloy hot piece is cooled at controlled temperature.
In the invention, the termination temperature of the temperature-controlled cooling is lower than the alpha phase alpha of the TiAl alloy2Phase transition temperature of the phase, said temperature-controlled coolingThe time cooling rate is less than or equal to 15 ℃/s, more preferably 5-15 ℃/s, the TiAl alloy is changed from alpha phase into multi-oriented gamma-ray photo layer structure and multi-oriented alpha2The photo layer is organized. The invention reduces the temperature to a stopping temperature lower than the alpha phase alpha of TiAl alloy by temperature-controlled cooling2In the phase transition temperature process of the phases, when the temperature is reduced to an alpha + gamma two-phase region, a gamma phase sheet layer is separated out from a high-temperature alpha mother phase, and because the high-temperature alpha mother phase has a multi-orientation characteristic, the formed gamma/alpha high-temperature two-phase sheet layer tissue is influenced by the solid phase transition phase relation and tissue inheritance, and also has the multi-orientation characteristic, and as the temperature is continuously reduced, the gamma photo layer is continuously separated out; when the temperature is reduced to be lower than the alpha phase alpha of TiAl alloy2At the phase transition temperature of the phase, the high-temperature alpha phase is orderly converted into alpha2Phase to finally form multi-oriented gamma/alpha2The lamellar structure and the state of the oriented columnar crystal are maintained.
In the invention, the termination temperature of the temperature-controlled cooling is preferably less than or equal to 800 ℃, and more preferably 600-750 ℃.
In the invention, the temperature-controlled cooling is preferably constant-speed cooling, and the cooling rate of the temperature-controlled cooling is 5-15 ℃/s, preferably 6-12 ℃/s.
The invention can not only realize the technical effect of thinning lamellar tissue, but also effectively inhibit the formation of non-equilibrium block phase by controlling the cooling rate.
After the temperature-controlled cooling is finished, the invention preferably selects the gamma-ray picture layer structure with multiple orientations and multiple orientations of alpha obtained by the temperature-controlled cooling2And cooling the TiAl alloy of the photo layer structure along with the furnace, and taking materials by introducing air.
The method provided by the invention has no melting and solidification processes, the process flow can be realized under a solid phase, the operation is simple, and the method is suitable for industrial production.
The invention provides the multi-orientation lamellar structure TiAl alloy with the initial solidification phase of the alpha phase, which is obtained by the preparation method in the technical scheme, wherein the atomic percent of Al element of the multi-orientation lamellar structure TiAl alloy is more than or equal to 47.5 at.%, and the multi-orientation lamellar structure is multi-orientation gamma phase and alpha phase2The volume percentage of the gamma-ray film structure is not less than90％。
The invention provides application of the multi-orientation lamellar structure TiAl alloy with the initial solidification phase of the alpha phase in aerospace. In the present invention, the multi-oriented lamellar-structure TiAl alloy is preferably used as the material for the aircraft engine.
The technical solution of the present invention will be clearly and completely described below with reference to the embodiments of the present invention. It is to be understood that the described embodiments are merely exemplary of the invention, and not restrictive of the full scope of the invention. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.
Example 1
Firstly, a master alloy bar (isometric crystal structure, length of 100mm) with the component of Ti-48Al (at.%) alloy is put into a directional heat treatment furnace, then the furnace is vacuumized, and the vacuum degree is 5 multiplied by 10-3Introducing argon gas to 500Pa while Pa, and repeating for 4 times.
And starting an induction heating power supply, heating the local part of the Ti-48Al master alloy bar by using a heating coil (the width of a thermal effect zone is 6mm), heating the TiAl alloy base metal in the effective hot zone from room temperature to 1200 ℃ at a heating rate of 20 ℃/s, heating the TiAl alloy base metal at 1200 ℃ to 1410 ℃ at a heating rate of 5 ℃/s, and preserving heat for 5min after heating to 1410 ℃.
Controlling the heating coil to move upwards relative to the Ti-48Al alloy bar at a moving speed of 5 mu m/s, controlling the temperature of the Ti-48Al alloy bar in the effective hot zone to be 1410 ℃ all the time in the moving process, and controlling the alloy bar to be in a solid phase state all the time in the relative directional movement process.
Stopping the relative directional movement, controlling the temperature and cooling, wherein the cooling rate is 10 ℃/s, when the temperature is cooled to be below 750 ℃, closing the heating power supply, carrying out furnace cooling on the Ti-48Al alloy bar, introducing air after the temperature is cooled to be below 100 ℃, opening the furnace door, and taking out the material.
FIG. 1 is an electron micrograph of the as-cast structure of a bar of a Ti-48Al (at.%) alloy of this example, and FIG. 2 is a multi-oriented bar prepared in this exampleGamma phase and alpha2As a result of analyzing fig. 1, 2 and 7, the cast structure of the Ti-48Al alloy is transformed from the equiaxed crystal structure to the columnar crystal structure of the lamellar structure by the method of this embodiment, and the columnar crystal structures of the lamellar structure coexist in a multi-orientation distribution.
Example 2
Firstly, a master alloy bar (isometric crystal structure, length of 100mm) with the component of Ti-48Al-2Cr-2Nb (at.%) alloy is put into a directional heat treatment furnace, then the furnace is vacuumized, and the vacuum degree is 1 multiplied by 10-3Introducing argon gas to 300Pa when Pa is needed, and repeating the steps for 3 times.
And starting an induction heating power supply, heating the local part of the Ti-48Al master alloy bar by using a heating coil (the width of a thermal effect region is 6mm), heating the Ti-48Al-2Cr-2Nb alloy master metal in the effective hot region from room temperature to 1200 ℃, at a heating rate of 10 ℃/s, heating the Ti-48Al-2Cr-2Nb alloy master metal to 1430 ℃ at a heating rate of 2 ℃/s, and keeping the temperature for 15min after heating to 1430 ℃.
Controlling the heating coil to move upwards relative to the Ti-48Al-2Cr-2Nb alloy bar at the moving speed of 2 mu m/s, controlling the temperature of the Ti-48Al alloy bar in the effective hot zone to be 1410 ℃ all the time in the moving process, and controlling the alloy bar to be in a solid phase state all the time in the relative directional movement process.
Stopping the relative directional movement, controlling the temperature and cooling, wherein the cooling rate is 5 ℃/s, when the temperature is cooled to be below 750 ℃, closing the heating power supply to cool the Ti-48Al-2Cr-2Nb alloy bar along with the furnace, introducing air after the temperature is cooled to be below 100 ℃, opening the furnace door, and taking out the material.
FIG. 4 is an as-cast structure electron micrograph of a bar of a master alloy of the Ti-48Al-2Cr-2Nb (at.%) alloy of this example, and FIG. 5 is an as-cast structure electron micrograph of a multi-oriented γ -phase and α -phase of the alloy of this example2As a result of analyzing FIG. 4, FIG. 5 and FIG. 7, the cast structure of Ti-48Al-2Cr-2Nb alloy is transformed from equiaxed crystal structure to lamellar columnar crystal structure by the method of this example, and the lamellar columnar crystal structure coexists in multi-orientation distribution.
Example 3
Firstly, a master alloy bar (isometric crystal structure, length of 100mm) with the component of Ti-48Al (at.%) alloy is put into a directional heat treatment furnace, then the furnace is vacuumized, and the vacuum degree is 5 multiplied by 10-3Introducing argon gas to 500Pa while Pa, and repeating for 4 times.
And starting an induction heating power supply, heating the local part of the Ti-48Al master alloy bar by using a heating coil (the width of a thermal effect zone is 6mm), heating the TiAl alloy base metal in the effective hot zone from room temperature to 1200 ℃ at a heating rate of 30 ℃/s, heating the TiAl alloy base metal at 1200 ℃ to 1410 ℃ at a heating rate of 3 ℃/s, and preserving heat for 10min after heating to 1410 ℃.
Controlling the heating coil to move upwards relative to the Ti-48Al alloy bar at a moving speed of 8 mu m/s, controlling the temperature of the Ti-48Al alloy bar in the effective hot zone to be 1410 ℃ all the time in the moving process, and keeping the alloy bar in a solid phase state all the time in the relative directional movement process.
Stopping the relative directional movement, carrying out temperature control cooling, wherein the cooling rate is 8 ℃/s, when the temperature is cooled to be below 750 ℃, closing a heating power supply, carrying out furnace cooling on the Ti-48Al alloy bar, introducing air after the temperature is cooled to be below 100 ℃, opening a furnace door, taking out the material, converting the cast structure of the Ti-48Al alloy from the isometric crystal structure into the columnar crystal structure of the lamellar structure, and enabling the columnar crystal structures of the lamellar structure to be in multi-orientation distribution and coexist.
Example 4
Firstly, a master alloy bar (isometric crystal structure, length of 100mm) with the component of Ti-48Al-2Cr-2Nb (at.%) alloy is put into a directional heat treatment furnace, then the furnace is vacuumized, and the vacuum degree is 1 multiplied by 10-3Introducing argon gas to 300Pa when Pa is needed, and repeating the steps for 3 times.
And starting an induction heating power supply, heating the local part of the Ti-48Al master alloy bar by using a heating coil (the width of a thermal effect region is 6mm), heating the Ti-48Al-2Cr-2Nb alloy master metal in the effective hot region from room temperature to 1200 ℃, wherein the heating rate is 15 ℃/s, the heating rate is 2.5 ℃/s when the temperature of the Ti-48Al-2Cr-2Nb alloy master metal in the effective hot region is increased to 1430 ℃, and then, preserving the heat for 15min after the temperature is increased to 1430 ℃.
Controlling the heating coil to move upwards relative to the Ti-48Al-2Cr-2Nb alloy bar with the moving speed of 5 mu m/s, controlling the temperature of the Ti-48Al alloy bar in the effective hot zone to be 1410 ℃ all the time in the moving process, and keeping the alloy bar in a solid phase state all the time in the relative directional movement process.
Stopping the relative directional movement, carrying out temperature control cooling, wherein the cooling rate is 6 ℃/s, when the temperature is cooled to be below 750 ℃, closing a heating power supply, carrying out furnace cooling on the Ti-48Al-2Cr-2Nb alloy bar, introducing air after the temperature is cooled to be below 100 ℃, opening a furnace door, taking out the material, converting the cast structure of the Ti-48Al-2Cr-2Nb alloy from the equiaxial crystal structure into the columnar crystal structure of the lamellar structure, and enabling the columnar crystal structures of the lamellar structure to be in multi-orientation distribution and coexist.
Test example 1
Mechanical property tests are performed on the products prepared in the embodiments 1 and 2, and the test results are shown in table 1 and fig. 3 to 4, and it can be obtained from table 1 and fig. 1 to 2 that the tensile stress is obviously reduced compared with that of the TiAl alloy with the multi-orientation lamellar structure prepared from the TiAl alloy raw material by the method provided by the invention under the same tensile strain, and the tensile strain of the product prepared by the method provided by the embodiment 1 of the invention can reach 1.5%, while the tensile strain of the raw material can only reach 0.4%; the tensile strain of the product prepared by the method provided by the embodiment 2 of the invention can reach 1.6%, while the tensile strain of the raw material can only reach 0.8%.
Tensile strain and tensile stress.
TABLE 1 test results for tensile stress of products and raw materials prepared in examples 1-2
The foregoing is only a preferred embodiment of the present invention, and it should be noted that, for those skilled in the art, various modifications and decorations can be made without departing from the principle of the present invention, and these modifications and decorations should also be regarded as the protection scope of the present invention.
Claims (9)
1. A preparation method of a multi-orientation lamellar structure TiAl alloy with an initial solidification phase of alpha phase comprises the following steps:
heating a local part of a TiAl alloy base material by using a heating device, heating the temperature of the TiAl alloy base material in an effective hot zone to the temperature of an alpha phase zone for heat preservation treatment to obtain a TiAl alloy heat preservation thermal part with a temperature gradient, wherein the TiAl alloy base material is an alpha phase solidified TiAl alloy; the volume ratio of the TiAl alloy base metal positioned in the effective hot zone to the TiAl alloy base metal is (4-10): 100;
the TiAl alloy heat-preservation hot piece and the heating device move relatively to carry out local heat treatment on the TiAl alloy heat-preservation hot piece to obtain a heat-treated alpha-phase TiAl alloy hot piece;
carrying out temperature control cooling on the heat-treated alpha-phase TiAl alloy hot piece, wherein in the process of temperature control cooling, the TiAl alloy is changed into a multi-oriented gamma phase and a multi-oriented alpha phase from an alpha phase2Photo layer structure, the termination temperature of the temperature-controlled cooling is lower than the alpha phase alpha of TiAl alloy2The phase transition temperature of the phase, and the cooling rate of the temperature-controlled cooling is less than or equal to 15 ℃/s.
2. The method according to claim 1, wherein the temperature of the α -phase region is 1370 to 1480 ℃ when the local portion of the TiAl alloy base material is heated.
3. The production method according to claim 1 or 2, wherein a temperature raising procedure of raising the temperature from room temperature to the temperature in the α -phase region when locally heating the TiAl alloy base material is: raising the temperature from room temperature to a first temperature according to a first temperature raising rate, and raising the temperature from the first temperature to the temperature of the alpha phase region according to a second temperature raising rate; the first temperature rise rate is 10-30 ℃/s, the second temperature rise rate is 2-5 ℃/s, and the first temperature is 1150-1250 ℃.
4. The preparation method according to claim 1, wherein the time of the heat preservation treatment is 5-15 min, the temperature of the TiAl alloy base material in the effective hot zone during the heat preservation treatment is alpha phase zone temperature, and the alpha phase zone temperature is 1370-1480 ℃.
5. The method according to claim 1, wherein the relative velocity of the relative movement is 2 to 10 μm/s.
6. The method according to claim 1, wherein during the local heat treatment, a volume ratio of the TiAl alloy base material to the TiAl alloy base material in the effective hot zone is (4-10): 100, a temperature of the TiAl alloy base material in the effective hot zone is an alpha phase zone temperature, and the alpha phase zone temperature is 1370-1480 ℃.
7. The method of claim 1, wherein the controlled temperature cooling has an end temperature of 800 ℃ or less.
8. The preparation method of any one of claims 1 to 7, wherein the initial solidification phase of the TiAl alloy is an alpha phase, the atomic percent of Al element in the TiAl alloy is not less than 47.5 at.%, and the multi-orientation lamellar structure is a multi-orientation gamma phase and alpha phase2The volume percentage of the gamma-ray film structure is more than or equal to 90 percent.
9. Use of the multi-oriented lamellar TiAl alloy with initial solidification phase of alpha phase as claimed in claim 8 in aerospace.
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| US5540792A (en) * | 1992-05-12 | 1996-07-30 | Forschungszentrum Julich Gmbh | Components based on intermetallic phases of the system titanium-aluminum and process for producing such components |
| FR2799335A1 (en) * | 1999-10-04 | 2001-04-06 | Centre Nat Rech Scient | Method for melting and solidification without contact of electrically conducting sample, notably containing meta-stable phase |
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| CN113481444A (en) * | 2021-07-05 | 2021-10-08 | 四川大学 | Method for regulating and controlling fine grain structure of peritectic solidification cast TiAl alloy |
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| DE10024343A1 (en) * | 2000-05-17 | 2001-11-22 | Gfe Met & Mat Gmbh | One-piece component used e.g. for valves in combustion engines has a lamella cast structure |
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| US5540792A (en) * | 1992-05-12 | 1996-07-30 | Forschungszentrum Julich Gmbh | Components based on intermetallic phases of the system titanium-aluminum and process for producing such components |
| FR2799335A1 (en) * | 1999-10-04 | 2001-04-06 | Centre Nat Rech Scient | Method for melting and solidification without contact of electrically conducting sample, notably containing meta-stable phase |
| JP2005097671A (en) * | 2003-09-24 | 2005-04-14 | Hitachi Cable Ltd | Ti-Al INTERMETALLIC COMPOUND AND MANUFACTURING METHOD THEREFOR |
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