CN117646137A - Gamma-TiAl alloy and heat treatment method thereof - Google Patents
Gamma-TiAl alloy and heat treatment method thereof Download PDFInfo
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- 239000000956 alloy Substances 0.000 title claims abstract description 219
- 229910045601 alloy Inorganic materials 0.000 title claims abstract description 209
- 229910006281 γ-TiAl Inorganic materials 0.000 title claims abstract description 91
- 238000000034 method Methods 0.000 title claims abstract description 44
- 238000010438 heat treatment Methods 0.000 title claims abstract description 40
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- WPBNNNQJVZRUHP-UHFFFAOYSA-L manganese(2+);methyl n-[[2-(methoxycarbonylcarbamothioylamino)phenyl]carbamothioyl]carbamate;n-[2-(sulfidocarbothioylamino)ethyl]carbamodithioate Chemical compound [Mn+2].[S-]C(=S)NCCNC([S-])=S.COC(=O)NC(=S)NC1=CC=CC=C1NC(=S)NC(=O)OC WPBNNNQJVZRUHP-UHFFFAOYSA-L 0.000 description 2
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Abstract
The invention discloses a gamma-TiAl alloy and a heat treatment method thereof, belonging to the technical field of alloys, wherein the method comprises the following steps: preparing a gamma-TiAl alloy cast ingot, wherein the solidification route of the gamma-TiAl alloy cast ingot passes through a beta single-phase region and an alpha single-phase region; performing thermal deformation treatment on the gamma-TiAl alloy cast ingot to obtain a deformed alloy; performing high-temperature treatment on the deformed alloy in the (alpha+gamma) two-phase region of the gamma-TiAl alloy ingot to obtain a high-temperature alloy; and (3) aging the high-temperature alloy to obtain the gamma-TiAl alloy after heat treatment. The invention realizes the technical effect of improving the mechanical property of the TiAl alloy material in a high-temperature environment by a heat treatment mode of high-temperature treatment and aging treatment in an (alpha+gamma) two-phase region.
Description
Technical Field
The invention relates to the technical field of alloys, in particular to a gamma-TiAl alloy and a heat treatment method thereof.
Background
The gamma-TiAl alloy has low density (3.8-4.2 g/cm) 3 ) The material has the unique advantages of high specific strength, high specific modulus, good creep resistance, good oxidation resistance and the like, and is a lightweight high-temperature-resistant material with great competitiveness for aviation power systems. However, poor room temperature plasticity and difficult high temperature forming due to the intermetallic nature have been key bottlenecks limiting their development and application.
Currently, the main TiAl alloy materials include cast alloys with high Al content (conventional γ -TiAl alloys) and β -solidified γ -TiAl alloys with low Al content. The cast alloy has coarse whole lamellar structure and low high-temperature strength. The beta-solidified gamma-TiAl alloy can retain part of beta phase in the high temperature process, and the beta phase can be orderly converted into beta after being retained at room temperature o The presence of this phase can impair the room temperature plasticity of the alloy, while affecting the high temperature properties of the alloy. Therefore, the existing TiAl alloy material also has the problem of poor mechanical property in a high-temperature environment.
Disclosure of Invention
The invention mainly aims to provide a gamma-TiAl alloy and a heat treatment method thereof, and aims to solve the problem that the existing TiAl alloy material is poor in mechanical property in a high-temperature environment.
In order to achieve the above object, the present invention provides a heat treatment method of a γ -TiAl alloy, comprising:
preparing a gamma-TiAl alloy cast ingot, wherein the solidification route of the gamma-TiAl alloy cast ingot passes through a beta single-phase region and an alpha single-phase region;
performing thermal deformation treatment on the gamma-TiAl alloy cast ingot to obtain a deformed alloy;
performing high-temperature treatment on the deformed alloy in an (alpha+gamma) two-phase region of the gamma-TiAl alloy ingot to obtain a high-temperature alloy;
and (3) aging the high-temperature alloy to obtain the gamma-TiAl alloy after heat treatment.
Optionally, the main system of the gamma-TiAl alloy cast ingot is Ti- (40-45) Al- (1-5) Mn- (0-1.0) Mo in atom percent.
Optionally, the main system of the gamma-TiAl alloy cast ingot is Ti- (43-45) Al- (1-2) Mn- (2-3.5) Nb in atom percent.
Optionally, the step of performing heat deformation treatment on the gamma-TiAl alloy ingot to obtain a deformed alloy is performed in a non-wrapping and non-isothermal atmospheric environment.
Optionally, the step of performing heat deformation treatment on the γ -TiAl alloy ingot to obtain a deformed alloy comprises the following steps:
the gamma-TiAl alloy ingot is insulated for 0.5h to 1h at the temperature of 1320 ℃ to 1380 ℃;
and carrying out hot forging or rolling deformation treatment on the gamma-TiAl alloy cast ingot subjected to heat preservation treatment, setting the initial deformation temperature to 1250-1350 ℃, setting the final deformation temperature to 1100-1150 ℃, and cooling in an air cooling mode after the heat deformation treatment to obtain the deformed alloy.
Optionally, the high temperature treatment time is 0.5h-1h.
Optionally, the temperature of the aging treatment is 800-850 ℃, and the time of the aging treatment is 3-6 h.
Optionally, the gamma-TiAl alloy cast ingot is prepared by adopting a vacuum induction and vacuum consumable integrated process, vacuum induction or plasma arc.
Optionally, the gamma-TiAl alloy comprises a first lamellar structure with a peak lamellar spacing of 30nm-60nm and a second lamellar structure with a peak lamellar spacing of 300nm-500 nm.
In addition, in order to achieve the above object, the present invention also provides a γ -TiAl alloy prepared by the heat treatment method of γ -TiAl alloy as described above.
The invention provides a heat treatment method of gamma-TiAl alloy, which is used for preparing gamma-TiAl alloy cast ingots with the characteristics that a solidification route passes through a beta single-phase region and an alpha single-phase region, and carrying out heat deformation treatment by utilizing the plasticity of high-temperature beta phase of the gamma-TiAl alloy cast ingots to prepare the gamma-TiAl alloy cast ingotsAfter the dissolution temperature of gamma phase is determined, the deformation alloy retains a certain proportion of coarse gamma sheet layers when the temperature of an (alpha+gamma) two-phase region is treated at high temperature, the coarse gamma sheet layers can play a role in pinning to a certain extent to prevent alpha phase grains from growing up, and then the fine gamma sheet layers are combined with ageing treatment to induce alpha phase precipitation between high Wenxiang regions or high-temperature coarse gamma sheet layers, so that a double-sheet-layer structure with different peak sheet layer spacing is finally formed, the high-temperature alpha phase is ensured not to be excessively roughened, and no beta exists at room temperature o The phase residue solves the problems of very thick crystal groups and low strong plasticity of the whole lamellar structure obtained by heat treatment of the alpha single-phase region in the traditional sense of the beta solidification gamma-TiAl alloy with the beta solidification characteristic and the alpha single-phase region, and further the prepared gamma-TiAl alloy has good high-temperature mechanical properties.
Drawings
FIG. 1 is a schematic flow chart of an embodiment of a method for heat treating a gamma-TiAl alloy according to the present invention;
FIG. 2 is a phase diagram of the Ti-43Al-1.5Mn-3Nb (at.%) alloy of example 1 of the present invention;
FIG. 3 is a schematic view showing the microstructure of example 1 of the present invention after 1250 ℃/0.5h/WC treatment;
FIG. 4 is a schematic view showing the microstructure of example 1 of the present invention after 1240 ℃ C./0.5 h/WC treatment;
FIG. 5 is a schematic view of the microstructure of the alloy of comparative example 1 of the present invention (1250 ℃/0.5h/AC+850 ℃/3h/FC treatment);
FIG. 6 is a schematic view showing the microstructure of an alloy of example 1 of the present invention (1210 ℃ C./0.5 h/AC+850 ℃ C./3 h/FC treatment);
FIG. 7 is a TEM test chart of the alloy of example 1 of the present invention (1210 ℃/0.5h/AC+850 ℃/3h/FC treatment);
FIG. 8 is a graph showing the tensile properties of hot rolled bars, bars of example 1 and bars of comparative example 1 according to the present invention;
FIG. 9 is a graph showing elongation test results of hot rolled bars, bars of example 1 and bars of comparative example 1 according to the present invention.
The achievement of the objects, functional features and advantages of the present invention will be further described with reference to the accompanying drawings, in conjunction with the embodiments.
Detailed Description
It should be understood that the specific embodiments described herein are for purposes of illustration only and are not intended to limit the scope of the invention.
The gamma-TiAl alloy has low density (3.8-4.2 g/cm) 3 ) The material has the unique advantages of high specific strength and specific modulus, good creep resistance, oxidation resistance and the like, belongs to a national strategic tip structural material, and is a light high-temperature resistant material with great competitive power for an aviation power system. However, poor room temperature plasticity and difficult high temperature forming due to the intermetallic nature have been key bottlenecks limiting their development and application. Similar to conventional materials, rational design of the TiAl alloy composition, structure is a prerequisite for obtaining high performance.
Since the 70 s of the 20 th century, two types of typical alloys, namely, cast alloys with high Al content (45 to 48 at.%) and beta-solidified γ -TiAl alloys with low Al content (40 to 45 at.%) have been developed by specialists in the TiAl field around whether the alloy solidification process has undergone peritectic reactions.
The solidification route of the cast alloy (also known as the traditional gamma-TiAl alloy) is as follows: the method comprises the steps of carrying out heat treatment on L- & gt beta- & gt alpha- & gt gamma- & gt alpha- & gt alpha+2- & gt gamma in an alpha single-phase region to obtain a full-lamellar tissue with good fracture toughness and creep resistance, wherein the full-lamellar tissue has high Al content and good room-temperature plasticity (2-3%), but the full-lamellar tissue has peritectic reaction in the solidification process, large component segregation, incapability of carrying out heat processing deformation, and coarse high-temperature strength, so that the temperature bearing capacity of the full-lamellar tissue is difficult to break through 650 ℃.
The current common solidification route for beta solidification gamma-TiAl alloys is generally: l- & gt, beta- & gt, alpha- & gamma- & gt o +α2+γ, the β phase (A2, im-3 m) has a sufficient number of independent phases due to the high temperature passing through the β single phase region<111>The {110} slip system makes the alloy show a certain hot working performance at high temperature, and the strength of the alloy is obviously higher than that of the cast alloy, and the temperature bearing capacity of the alloy can reach 720 ℃. However, due to the strong action of the beta phase stabilizing element, the beta phase of the high-temperature part of the alloy cannot be completely converted into alpha phase, so that the full lamellar microstructure with engineering application value cannot be regulated and controlled through conventional heat treatment. On the other hand, high Wenxiang is ensuredAfter being left at room temperature, the mixture is orderly converted into beta o The existence of the phase can damage the room temperature plasticity of the alloy, and simultaneously affect the high temperature performance of the alloy, so that the temperature bearing capacity of the alloy is difficult to break through 750 ℃.
In order to ensure that the gamma-TiAl alloy has good hot workability and higher temperature bearing capacity, a novel beta-solidification gamma-TiAl alloy with beta solidification characteristics and an alpha single-phase region can be designed, namely, an ideal solidification route is as follows: l- & gt, beta- & gt, alpha 2- & gamma+ (beta) o ) The aim is to utilize the plasticity of high Wenxiang to realize good thermal deformation of the alloy, eliminate the residual beta o phase in the alloy by combining the heat treatment in an alpha single-phase region, form a full lamellar structure and ensure that the alloy has good high-temperature strength at 750 ℃ and above. However, similar to the traditional gamma-TiAl alloy, when the alpha single-phase region is subjected to heat treatment to regulate and control the whole lamellar structure, alpha phase grains are obviously coarsened due to the lack of pinning phase, so that the finally obtained whole lamellar structure lamellar crystal group is very coarse (200-1000 mu m), the strength and plasticity of the alloy are still lower, and the alloy deviates from the original purpose of alloy design. For conventional gamma-TiAl alloys, a large amount of refined grain elements, such as Ti-45Al-2Mn-2Nb (45 XD), may be added, often requiring up to 1% B to refine the full lamellar structure. However, for β -solidified γ -TiAl alloys, the amount of refined grain element addition such as B needs to be controlled to be not higher than 0.1%, beyond which the object of refining the α -phase size is not achieved, and even the overall properties of the alloy are adversely affected.
The embodiment of the invention provides a heat treatment method of gamma-TiAl alloy, referring to FIG. 1, FIG. 1 is a schematic flow chart of an embodiment of the heat treatment method of gamma-TiAl alloy.
In this embodiment, the heat treatment method of the γ -TiAl alloy includes:
and S10, preparing a gamma-TiAl alloy cast ingot, wherein the solidification route of the gamma-TiAl alloy cast ingot passes through the beta single-phase region and the alpha single-phase region.
The gamma-TiAl alloy is an alloy material with two elements of Ti and Al as main components. The microstructure of the gamma-TiAl alloy is mainly gamma-phase, and the content of Al element is generally a main factor for determining the solidification route under the conventional cooling speed, and different room temperature tissues can be obtained by different solidification routes. The beta-solidification gamma-TiAl alloy refers to a gamma-TiAl alloy with a solidification route passing through a beta single-phase region, and the content of Al element is generally low through the regulation and control of alloy components, so that certain hot processing performance is shown at high temperature, and the strength is also improved. The embodiment further regulates and controls alloy components on the basis of the beta-solidification gamma-TiAl alloy, so that the beta-solidification gamma-TiAl alloy also has the characteristic of an alpha single-phase region.
Alternatively, the solidification route of the γ -TiAl alloy ingot of this embodiment is: l- & gt L- & gtbeta- & gt beta- & ltalpha- & gtalpha 2 +γ, wherein L represents Lquid liquid phase, α, β, γ, α, passing through the β single phase region and the α single phase region 2 All are solid phases, L+beta represents coexistence of L phase and beta phase, beta+alpha represents coexistence of beta phase and alpha phase, and alpha represents 2 The phases and gamma phase coexist. In the solidification route, alpha-alpha 2 The eutectoid transformation of +gamma occurs.
Optionally, a gamma-TiAl alloy ingot is prepared by smelting in a mode of a vacuum induction and vacuum consumable integrated process, vacuum induction or plasma arc. Vacuum induction refers to a process of melting metal in a vacuum environment using eddy currents generated by electromagnetic induction. Vacuum consumable refers to a method that under vacuum, a material to be melted is used as one electrode, a water-cooled copper crucible is used as the other electrode, an arc is generated between the two electrodes, the material to be melted is melted by the electric arc at high temperature, and then is dripped into the crucible, and the melted material is gradually melted and gradually condensed into an ingot. The vacuum consumable can be combined with vacuum induction, namely, the raw materials are smelted by adopting a comprehensive process of vacuum induction and vacuum consumable, and the gamma-TiAl alloy cast ingot is obtained. The smelting mode can be selected according to actual needs.
Alternatively, the main system of the gamma-TiAl alloy cast ingot is Ti- (40-45) Al- (1-5) Mn- (0-1.0) Mo, for example, ti-44.8Al-3.6Mn-0.6Mo, ti-42Al-2.5Mn-0.3Mo. Mo is added into Ti-Al-Mn series alloy, the alloy can be subjected to thermal deformation treatment under the conditions of no sheath and non-isothermal, the content range of Al element is large, and the alloy has good tissue stability and oxidation resistance.
Alternatively, the main system of the gamma-TiAl alloy cast ingot is Ti- (43-45) Al- (1-2) Mn- (2-3.5) Nb, for example, ti-43Al-1.5Mn-3Nb, ti-44Al-1.8Mn-3.2Nb, in atomic percent. A small amount of Mn and Nb are added into the TiAl alloy, the alloy can be subjected to heat deformation treatment under the conditions of no sheath and non-isothermal temperature, the content of Nb element is low, and the high-temperature oxidation resistance is good.
And S20, performing thermal deformation treatment on the gamma-TiAl alloy cast ingot to obtain a deformed alloy.
The heat deformation treatment is a method of processing an ingot into a material piece having a predetermined shape at a predetermined temperature. The deformation alloy is an alloy material obtained by heat deformation treatment of a gamma-TiAl alloy cast ingot. The heat deformation treatment in the present embodiment may include hot forging and rolling deformation.
Alternatively, the heat deformation treatment process of the gamma-TiAl alloy ingot can be performed in a non-jacketed and non-isothermal atmospheric environment. Through the regulation and control of alloy components, the solidification route of the gamma-TiAl alloy passes through the beta single-phase region and the alpha single-phase region, has good oxidation resistance in the high-temperature processing process, can be suitable for environment conditions without a sheath and non-isothermal, and reduces the difficulty and cost of thermal deformation processing.
In a possible embodiment, step S20 includes:
s21, preserving heat of the gamma-TiAl alloy ingot for 0.5-1 h at the temperature of 1320-1380 ℃;
the heat preservation treatment is carried out before the hot forging or rolling deformation treatment, so that the microstructure of the cast ingot can be regulated and controlled. The temperature of the heat-insulating treatment is 1320-1380 ℃, for example 1320 ℃, 1330 ℃, 1340 ℃, 1350 ℃, 1360 ℃, 1370 ℃ and 1380 ℃. The heat preservation treatment time is 0.5h-1h, for example, 0.5h, 0.6h, 0.7h, 0.8h, 0.9h, 1h.
And S22, performing hot forging or rolling deformation treatment on the gamma-TiAl alloy cast ingot subjected to heat preservation treatment, setting the initial deformation temperature to 1250-1350 ℃, the final deformation temperature to 1100-1150 ℃, and performing cooling after heat deformation treatment in an air cooling mode to obtain the deformed alloy.
The gamma-TiAl alloy cast ingot can be subjected to multiple upsetting and drawing in the hot forging treatment process. The rolling deformation treatment reduces the section of the gamma-TiAl alloy cast ingot through the compression of the roller, and the length is increased. The specific process of the heat deformation treatment can be selected according to actual needs. The initial deformation temperature of the heat deformation treatment is set to 1250 ℃ to 1350 ℃, for example, 1250 ℃, 1270 ℃, 1290 ℃, 1310 ℃, 1330 ℃, 1350 ℃. The final deformation temperature of the heat deformation treatment is set to 1100-1150 ℃, for example, 1100 ℃, 1110 ℃, 1120 ℃, 1130 ℃, 1140 ℃, 1150 ℃. And performing air cooling after the thermal deformation treatment to obtain the deformed alloy with a certain shape. The shape of the wrought alloy can be set according to the needs, and comprises shapes such as bars, plates and the like.
And S30, performing high-temperature treatment on the deformed alloy in an (alpha+gamma) two-phase region of the gamma-TiAl alloy ingot to obtain a high-temperature alloy.
The (α+γ) two-phase region refers to a temperature interval in which an α phase and a γ phase coexist during solidification of the γ -TiAl alloy. Gamma phase dissolution temperature (using T γ,solv Representation) is related to the alloy composition ratio in the gamma-TiAl alloy cast ingot. The gamma-phase dissolution temperature of the gamma-TiAl alloy ingot can be calculated by thermodynamic calculation software, and then the calculated gamma-phase dissolution temperature is verified to determine the actual gamma-phase dissolution temperature.
In a possible implementation manner, the component proportion of the gamma-TiAl alloy cast ingot is input into thermodynamic calculation software to obtain an initial gamma-phase dissolution temperature t1, a plurality of samples are cut from the prepared gamma-TiAl alloy cast ingot, the samples are respectively insulated for 1h in a temperature range of t1+/-20 ℃, then water cooling is carried out to room temperature, the samples are polished and then are placed under an electronic probe for observation, and the gamma-phase dissolution temperature is determined through the observed tissue morphology. Above the gamma-phase dissolution temperature, the microstructure is substantially pure alpha 2 A phase, below the gamma phase dissolution temperature, the microstructure comprising alpha 2 +γ two phases. The (alpha+gamma) two-phase region is below the gamma-phase dissolution temperature, alpha 2 Above the phase dissolution temperature.
Optionally, in the step of subjecting the wrought alloy to a high temperature treatment in the (α+γ) two-phase region to obtain a high temperature alloy, the time of the high temperature treatment is 0.5h to 1h, for example, 0.5h, 0.6h, 0.7h, 0.8h, 0.9h, 1h. And a certain proportion of coarse gamma sheet layers are reserved during high-temperature treatment of the (alpha+gamma) two-phase region, and the part of coarse gamma sheet layers can play a role in pinning alpha phase grain growth to a certain extent.
And step S40, aging treatment is carried out on the high-temperature alloy, and the gamma-TiAl alloy after heat treatment is obtained.
Aging treatment refers to a heat treatment process that a metal or alloy workpiece is subjected to cold working deformation to a certain extent, then is placed at a higher temperature or room temperature to keep the shape and the size, and the performance changes with time. Alternatively, the temperature of the aging treatment is set at 800-850 ℃, e.g., 800 ℃, 810 ℃, 820 ℃, 830 ℃, 840 ℃, 850 ℃, and the time of the aging treatment is set at 3-6 h, e.g., 3h, 3.5h, 4h, 4.5h, 5h, 5.5h, 6h. Aging treatment induces alpha phase precipitation of fine gamma sheets between high Wenxiang areas or high-temperature coarse gamma sheets, and the coarse gamma sheets reserved in (alpha+gamma) two-phase areas by high-temperature treatment are finally formed into double-sheet tissues with different peak sheet spacing sizes. The fine gamma lamellae may be distributed individually in a certain area or may be distributed among the coarse gamma lamellae.
In the embodiment, preparing a gamma-TiAl alloy cast ingot with a solidification route passing through a beta single-phase region and an alpha single-phase region, performing thermal deformation treatment by utilizing the plasticity of a high-temperature beta phase of the gamma-TiAl alloy cast ingot to prepare a deformed alloy with a certain shape, after determining the dissolution temperature of the gamma phase, retaining a certain proportion of coarse gamma sheets when the deformed alloy is subjected to high-temperature treatment at the temperature of an (alpha+gamma) two-phase region, wherein the coarse gamma sheets can play a role of pinning to a certain extent to prevent the growth of alpha phase grains, and combining with aging treatment to induce alpha phase precipitation of fine gamma sheets between the high Wenxiang region or the high-temperature coarse gamma sheets to finally form a double-sheet structure with different peak sheet spacing, so that the high-temperature alpha phase is ensured not to be coarsened excessively at room temperature without beta o The phase residue solves the problems of very thick crystal groups and low strong plasticity of the whole lamellar structure obtained by heat treatment of the alpha single-phase region in the traditional sense of the beta solidification gamma-TiAl alloy with the beta solidification characteristic and the alpha single-phase region, and further the prepared gamma-TiAl alloy has good high-temperature mechanical properties.
The embodiment of the invention also provides a gamma-TiAl alloy, which is prepared by adopting the heat treatment method of the gamma-TiAl alloy. The prepared gamma-TiAl alloy comprises a first lamellar structure with a peak lamellar spacing of 30-60 nm and a second lamellar structure with a peak lamellar spacing of 300-500 nm, and the lamellar size can be controlled to be 30-60 mu m. The fine gamma sheets can be distributed in a certain area alone or among the coarse gamma sheets, and a first sheet structure with relatively smaller peak sheet spacing and a second sheet structure with relatively larger peak sheet spacing are formed due to the difference of the distribution areas of the fine gamma sheets.
After the thermal deformation treatment, a small and full-lamellar structure can be regulated and controlled by a simpler two-step heat treatment process without adding a large amount of refined grain elements, namely high-temperature treatment and aging treatment at 800-850 ℃ in an (alpha+gamma) two-phase region, so that the alloy has good room temperature, high-temperature strength and plasticity. The gamma-TiAl alloy of the embodiment of the invention has the beta solidification characteristic and the alpha single-phase region, belongs to novel beta solidification gamma-TiAl alloy, can realize low-cost thermal deformation under non-isothermal conditions without a sheath, and can regulate and control the whole lamellar structure with lamellar group size within 30-60 mu m. The double-lamellar structure with two peak lamellar spacing can ensure not only that the high-temperature alpha phase is not excessively coarsened, but also that the room temperature beta-free o The residue of the phase and the double-lamellar structure of the two proportions can effectively ensure that the alloy has good strength and plasticity.
Example 1
The alloy selected in this example 1 had the main composition: ti-43Al-1.5Mn-3Nb (at%).
The preparation method of the alloy in the embodiment 1 comprises the following steps: the main raw materials for preparing the alloy are sponge titanium, industrial pure aluminum, purified manganese, aluminum and niobium intermediate alloy. Smelting 20kg of alloy material by adopting a vacuum induction smelting furnace, and casting into 4 alloy materials with the size ofIs a cast alloy ingot. The alloy ingot is directly rolled into bars with the diameter of 12mm by adopting a Y-type rolling machine for one-time multi-pass rolling, and the initial heating temperature of rolling is 1380 ℃.
T of example 1 alloy γ,solv And (3) determining: (1) The phase transition route of the alloy was calculated using pandatm (2023) thermodynamic calculation software to obtain a phase diagram of the Ti-43Al-1.5Mn-3Nb (at.%) alloy as shown in fig. 2, where the abscissa represents temperature in degrees celsius and the ordinate represents phase composition in%. As can be seen from fig. 2, the solidification route of the example alloy is: l- & gt L- & gtbeta- & gt beta- & ltalpha- & gtalpha 2 +gamma, simultaneously satisfying the characteristic of beta solidification and having an alpha single-phase region, belongs to the research object of the invention. By analysis of the phase diagram of the alloy shown in FIG. 2, the gamma-phase dissolution temperature (T γ,solv ) Equal to about 1240 c.
(2) Series of samples with the diameter of 8mm and the thickness of 8mm are cut from alloy cast ingots, the series of samples are respectively insulated for 1h at 1260-1220 ℃, and then Water Cooling (WC) is carried out to room temperature. The polished tissues of the above series of treated samples were observed under the condition of a back scattered electron mode (BSE) mode using a JXA-8530F Electron Probe (EPMA). FIG. 3 shows the microstructure after 1250℃treatment, and as can be seen from FIG. 3, the corresponding microstructure after 1250℃C/0.5 h/WC treatment is essentially pure α 2 A phase; FIG. 4 shows the microstructure after 1240℃treatment, and from FIG. 4 it can be seen that the corresponding microstructure after 1240℃C/0.5 h/WC treatment is α 2 Sheet and alpha of gamma 2 The phase being alpha 2 +γ two-phase constitution. FIGS. 3 and 4 show that the alloy has a T γ,solv About 1250 c with a deviation of approximately 10 c from thermodynamic calculations.
Heat treatment of the alloy of example 1: carrying out high-temperature treatment on the rolled bar at 1210 ℃ (alpha+gamma) two-phase region for 0.5h, and air-cooling (AC) to room temperature after the treatment is finished; then aging treatment is carried out for 3 hours at 850 ℃, and the cooling mode after aging is Furnace Cooling (FC).
Comparative example 1
The alloy selected in this comparative example 1 had the main composition: ti-43Al-1.5Mn-3Nb (at%).
The preparation method of the alloy of the comparative example 1 comprises the following steps: the main raw materials for preparing the alloy are sponge titanium, industrial pure aluminum, purified manganese, aluminum and niobium intermediate alloy. Smelting 20kg of alloy material by adopting a vacuum induction smelting furnace, and casting into 4 alloy materials with the size ofThe alloy ingot is directly rolled into bars with the diameter of 12mm by adopting a Y-type rolling machine for one-time multi-pass rolling, and the initial heating temperature of rolling is 1380 ℃.
Comparative example 1 alloy T γ,solv And (3) determining: the main component of the comparative alloy is the same as that of the example, see the alloy T of the above example γ,solv Procedure for determination, determination of T of comparative example alloy γ,solv About 1250 c.
Heat treatment of the alloy of comparative example 1: carrying out high-temperature treatment on the rolled bar at 1250 ℃ (alpha single-phase area) for 0.5h, and air-cooling (AC) to room temperature after the treatment is finished; then aging treatment is carried out for 3 hours at 850 ℃, and the cooling mode after aging is Furnace Cooling (FC).
Test results and analysis
Tissue analysis: the polished tissues of the above series of treated samples were observed under the condition of a back scattered electron mode (BSE) mode using a JXA-8530F Electron Probe (EPMA), and lamellar structure features in the microstructure were analyzed by Talos F200X field emission transmission electron microscopy.
FIG. 5 is a microstructure of the alloy of comparative example 1 (1250 ℃ C./0.5 h/AC+850 ℃ C./3 h/FC treatment), and it can be seen that a full lamellar structure is obtained at the alpha single phase zone treatment, with an average lamellar grain size of about 300 μm.
FIG. 6 shows the microstructure of the alloy of example 1 (1210 ℃ C./0.5 h/AC+850 ℃ C./3 h/FC treatment), and it can be seen that the whole lamellar structure is obtained in the (α+γ) two-phase region treatment, with an average lamellar colony size of about 50. Mu.m. However, this full lamellar structure differs from the result of FIG. 5 in that the lamellar structure comprises two lamellar structures with peak lamellar spacing, i.e. a biplate structure, the fine and coarse lamellar layers being defined as Iα respectively 2 "gamma" (first sheet of girald) and "IIalpha 2 Gamma lamellar (second lamellar structure). FIG. 7 is a TEM test chart of the alloy of example 1 (1210 ℃ C./0.5 h/AC+850 ℃ C./3 h/FC treatment), based on TEM analysis of the double lamellar structure of FIG. 7, the double lamellar spacing of 50nm and 500nm, respectively.
Tensile property analysis: standard tensile test pieces were sampled from the hot rolled bars after heat deformation treatment, the rolled bars of example 1 and comparative example 1 after final heat treatment, and tensile test tests at room temperature, 750 ℃,800 ℃ and 850 ℃ were performed on a stretcher to evaluate their comprehensive mechanical properties (room temperature and high temperature tensile properties were respectively subjected to GB/T228.1-2010 and GB/T228.2-2015 standards).
FIG. 8 is a tensile property test result of a hot rolled bar, a bar of example 1 and a bar of comparative example 1 (at room temperature, 750 ℃,800 ℃, 850 ℃), wherein As-rolled represents a hot rolled bar, 1250 ℃/0.5h/AC+850 ℃/3h/FC represents a bar prepared in comparative example 1, and 1210 ℃/0.5h/AC+850 ℃/3h/FC represents a bar prepared in example 1. FIG. 9 shows elongation test results at room temperature, 750 ℃,800 ℃, 850 ℃ and 850 ℃ for hot rolled bars, example 1 bars and comparative example 1 bars (at room temperature, 750 ℃,800 ℃, 850 ℃) wherein As-rolled represents a hot rolled bar, 1250 ℃/0.5h/AC+850 ℃/3h/FC represents a comparative example bar, 1210 ℃/0.5h/AC+850 ℃/3h/FC represents an example bar. As can be seen from fig. 8 and 9, the double lamellar structure obtained by the (α+γ) two-phase region treatment has an optimal strength, plastic fit, which is significantly better than the conventional meaning of the full lamellar structure obtained by the hot rolled state and α single-phase region treatment. Specifically, the intensity of the coarse whole lamellar layer in the traditional sense is even lower than that of the hot rolled state, and the intensity and plasticity of the double lamellar layer structure at 800 ℃ and 850 ℃ provided by the embodiment of the invention reach 791MPa and 3.5%,683MPa and 4.0%, which are obviously better than 653MPa and 1.0%,579MPa and 1.5% of the intensity and plasticity at 800 ℃ and 850 ℃ in the hot rolled state.
The foregoing embodiment numbers of the present invention are merely for the purpose of description, and do not represent the advantages or disadvantages of the embodiments.
The foregoing description is only of the preferred embodiments of the present invention, and is not intended to limit the scope of the invention, but rather is intended to cover any equivalents of the structures or equivalent processes disclosed herein or in the alternative, which may be employed directly or indirectly in other related arts.
Claims (10)
1. A method for heat treatment of a γ -TiAl alloy, characterized in that the method for heat treatment of a γ -TiAl alloy comprises the steps of:
preparing a gamma-TiAl alloy cast ingot, wherein the solidification route of the gamma-TiAl alloy cast ingot passes through a beta single-phase region and an alpha single-phase region;
performing thermal deformation treatment on the gamma-TiAl alloy cast ingot to obtain a deformed alloy;
performing high-temperature treatment on the deformed alloy in an (alpha+gamma) two-phase region of the gamma-TiAl alloy ingot to obtain a high-temperature alloy;
and (3) aging the high-temperature alloy to obtain the gamma-TiAl alloy after heat treatment.
2. The method for heat treatment of gamma-TiAl alloy according to claim 1, wherein the main system of the gamma-TiAl alloy ingot is Ti- (40-45) Al- (1-5) Mn- (0-1.0) Mo in atom percent.
3. The method for heat treatment of gamma-TiAl alloy according to claim 1, wherein the main system of the gamma-TiAl alloy ingot is Ti- (43-45) Al- (1-2) Mn- (2-3.5) Nb in atom percent.
4. The method of claim 1, wherein the step of heat deforming the gamma-TiAl alloy ingot to obtain a wrought alloy is performed in a non-jacketed and non-isothermal atmospheric environment.
5. The method for heat treatment of γ -TiAl alloy according to claim 4, wherein the step of heat-deforming the γ -TiAl alloy ingot to obtain a deformed alloy comprises:
the gamma-TiAl alloy ingot is insulated for 0.5h to 1h at the temperature of 1320 ℃ to 1380 ℃;
and carrying out hot forging or rolling deformation treatment on the gamma-TiAl alloy cast ingot subjected to heat preservation treatment, setting the initial deformation temperature to 1250-1350 ℃, setting the final deformation temperature to 1100-1150 ℃, and cooling in an air cooling mode after the heat deformation treatment to obtain the deformed alloy.
6. The method for heat treatment of γ -TiAl alloy according to claim 1, wherein the time of the high temperature treatment is 0.5h to 1h.
7. The method for heat treatment of gamma-TiAl alloy according to claim 1, wherein the temperature of the aging treatment is 800-850 ℃, and the time of the aging treatment is 3-6 h.
8. The method for heat treatment of gamma-TiAl alloy according to claim 1, wherein the gamma-TiAl alloy ingot is prepared by adopting a vacuum induction and vacuum consumable integrated process, vacuum induction or plasma arc.
9. The method of heat treatment of a γ -TiAl alloy according to any of claims 1-8, wherein the γ -TiAl alloy comprises a first lamellar structure having a peak lamellar spacing of 30nm-60nm and a second lamellar structure having a peak lamellar spacing of 300nm-500 nm.
10. A gamma-TiAl alloy prepared by a heat treatment process according to any one of claims 1 to 9.
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