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CN-117587295-B - Is rich in large-size alpha2TiAl alloy of phase twinning and preparation method thereof

CN117587295BCN 117587295 BCN117587295 BCN 117587295BCN-117587295-B

Abstract

The invention provides a TiAl alloy rich in large-size alpha 2 phase twins, in particular a second-class twins, which contains 34-36at.% Al, 7-8at.% Nb, and the balance of Ti and unavoidable impurities. The invention also provides a method for preparing the TiAl alloy rich in the large-size alpha 2 phase second twin crystal, which comprises the steps of carrying out homogenization treatment at 1200 ℃ for 9-12 hours after an ingot of the alloy is obtained through vacuum arc furnace smelting, and then carrying out quenching after the temperature is kept at 900-1000 ℃ for 3-6 hours to obtain the TiAl alloy rich in the large-size alpha 2 phase second twin crystal. The alloy can generate a large amount of second-class twin crystals with large size, provides a proper research material for research of deformed twin crystals, solves the problem that the deformed twin crystals are difficult to characterize and research, and provides a foundation for further strengthening of alloy performance.

Inventors

  • SONG LIN
  • LIU WENHAO
  • ZHANG TIEBANG

Assignees

  • 西北工业大学

Dates

Publication Date
20260508
Application Date
20231127

Claims (6)

  1. 1. A process for producing a large-size alpha 2 -phase twinned TiAl alloy, characterized in that the large-size alpha 2 -phase twinned TiAl alloy contains 34 to 36at.% Al, 7 to 8at.% Nb, the balance being Ti and unavoidable impurities, After the alloy ingot is obtained through vacuum arc furnace smelting, carrying out homogenization treatment at 1100-1300 ℃ for 9-12 hours, then quenching after heat preservation at 900-1000 ℃ for 3-6 hours, After the homogenization treatment and the quenching, the TiAl alloy is subjected to a thermal compression deformation having a deformation amount of 10-15%, the thermal compression deformation being performed at a deformation rate of 0.01s -1 at 900-1000 ℃.
  2. 2. The method for producing a large-size α 2 -phase second-twinned TiAl alloy according to claim 1, characterized in that after the ingot of the alloy is obtained by vacuum arc furnace melting, homogenization treatment is carried out at 1200 ℃ for 10 hours, followed by quenching after heat preservation at 900-1000 ℃ for 5 hours.
  3. 3. A method of enriching a large-size alpha 2 phase second-class twinned TiAl alloy according to claim 1 or 2, comprising the steps of: Step (1) batching Taking a zero-order sponge titanium, high-purity aluminum and niobium aluminum alloy smelting cast ingot as raw materials, uniformly mixing according to the component proportion, preparing a standby sample with a certain mass, and additionally adding 3 wt percent of Al during the batching to compensate element loss possibly occurring during smelting in order to prevent a large amount of volatilization of Al during smelting; step (2) smelting cast ingots Melting the raw materials in the step (1) into ingots by adopting a vacuum arc melting furnace (VAR) or a vacuum skull furnace, and repeating the melting process for 5 times; Step (3) Heat treatment Firstly homogenizing the TiAl alloy cast ingot obtained by smelting, and then adjusting the structure into a two-phase structure through heat treatment; Step (4) wire cutting Cutting a cylinder from the central part of the cast ingot by a numerical control linear cutting machine; Step (5) thermal deformation And carrying out thermal compression deformation on the cut compressed sample after the heat treatment, wherein the deformation is 10% -20%.
  4. 4. The method of claim 3, wherein the large-size alpha 2 phase second-class twinning-enriched TiAl alloy, In the step (2), under the condition that the raw materials in the step (1) are melted into ingots by adopting a vacuum arc melting furnace, the melting process is repeated for 5 times, each time of melting from the second time, the ingots are required to be turned over to obtain ingots with uniform components, the melting vacuum degree is controlled to be lower than 0.1Pa, and the melting current is controlled to be in the range of 0.2 kA-0.3 kA.
  5. 5. A method of enriching a large-size α 2 -phase second-kind twin-crystal-rich TiAl alloy according to claim 3, wherein in the step (3) heat treatment, the homogenization treatment is to put the ingot into a heat treatment furnace and furnace-cool after holding at 1200 ℃ for 10 hours.
  6. 6. A method of preparing a large-size alpha 2 phase second-class twinned TiAl alloy according to claim 3, wherein in the heat treatment of step (3), the structure is adjusted to a two-phase structure by the heat treatment, specifically, the homogenized sample is placed in a heat treatment furnace, kept at 1000 ℃ for 5 hours, and then taken out and rapidly quenched in normal temperature water.

Description

TiAl alloy rich in large-size alpha 2 phase twin crystals and preparation method thereof Technical Field The invention relates to a novel TiAl alloy and a preparation method thereof, in particular to a TiAl alloy rich in large-size alpha 2 phase twin crystals and a preparation method thereof, and especially relates to a TiAl alloy rich in large-size alpha 2 phase second-class twin crystals and a preparation method thereof. Background The TiAl alloy has a series of advantages of low density, high specific strength, high specific stiffness, good oxidation resistance, good high-temperature creep property and the like, has wide application prospect in the aerospace field, and particularly has a weight reduction effect in a 600-800 ℃ range, so that the TiAl alloy is expected to replace high-temperature titanium alloy to be used as a material of a low-pressure turbine blade, and becomes a next-generation light high-temperature structural material. Therefore, the scholars have conducted research on improvement of the mechanical properties of the TiAl alloy from various angles. Among them, deformation behavior has been the focus of research because of significant impact on mechanical properties of alloys, where slip and twinning are two major plastic deformation mechanisms of metallic materials. For TiAl alloys, the α 2 phase is one of its main constituent phases, and particularly for the hexagonal α 2 phase, the deformed twins appear more important in plastic deformation due to the less slip system. It is generally considered that the generation of deformed twins is very difficult due to the ordered structure of the α 2 phase, which is also considered as one of the reasons for poor plasticity of the α 2 phase. Previous studies considered that in the Ti 3 Al alloy having an Al content in accordance with the stoichiometric ratio (Al content is 25 at%), no deformation twinning was generated in the α 2 phase. In recent years, {202 (-) 1} α 2 compression twins have been found in γ -TiAl alloys having a high Al content (44 at%) after deformation under specific conditions. However, the twin crystal has small size and only has nano-scale, the difficulty of the characterization and research of the nano-scale structure is high, and the method can be generally carried out only by using a Transmission Electron Microscope (TEM), has high cost and great difficulty, so that the prior academy still has little knowledge about the related mechanism of alpha 2 deformation twin crystal. Therefore, to deepen understanding the mechanism related to the deformation twinning of the alpha 2 needs to reduce the difficulty of characterization and increase the size of twinning. However, in the γ -TiAl alloy, α 2 exists as a lamellar structure, and the size itself is small, limiting the size of the twin. Thus, to obtain a twin crystal of a large size for a related study, it is necessary to redesign the alloy composition. 20 years ago, kishida et Al have found that, in non-stoichiometric Ti 3 Al single crystals, when deformed at temperatures above 1000 ℃, the second twin species will appear in Ti 3 Al as a result of the formation of '{2 (-) 121 (-) 0 (-) 3 }'. The twin crystal has high content and large size, is beneficial to reducing the characterization difficulty, and deepens the understanding of the related mechanism of alpha 2 deformation twin crystal. However, the preparation of the single crystal is difficult, the cost is high, the mechanical property is poor, and the single crystal cannot be really put into practice. In view of this, the inventors of the present invention have desired to devise a novel alloy which is easy to generate α 2 deformed twin, particularly a second-type twin, which can be prepared by a melting method, is simple and easy to obtain relative to single crystals, and generates a large amount of large-size second-type twin in the deformed alloy, so as to provide a suitable research material for research of deformed twin, solve the problem that deformed twin is difficult to characterize research, and provide a foundation for further strengthening of alloy performance. Disclosure of Invention Therefore, in order to deeply study the effect of alpha 2 phase-change twin crystals in the plastic deformation of Ti 3 Al alloy, the problems of difficult preparation, high cost, poor mechanical property and lack of application value of the second-class twin crystal single crystal of the existing Ti 3 Al '{2 (-) 12 (-) 1 (-) 0 (-) 3}' are overcome. Compared with alpha 2 phase in the traditional TiAl alloy which is difficult to generate deformation twin crystals, the novel alloy designed by the invention can generate a large number of micron-sized '{2 (-) 12 (-) 0 (-) 3}' second-class alpha 2 twin crystals after deformation, provides a basis for the research of alpha 2 phase-change twin crystals and the improvement of alloy performance, provides a proper research material for the research of deformation twin crystals, solves the p