阅读说明：本技术 一种高抗氧化、高塑性的变形TiAl基合金及其制备工艺 (High-oxidation-resistance and high-plasticity deformed TiAl-based alloy and preparation process thereof ) 是由 李小兵 刘奎 高明 张孟殊 舒磊 马颖澈 于 2020-04-16 设计创作，主要内容包括：本发明公开了一种高抗氧化、高塑性的变形TiAl基合金,属于TiAl基合金技术领域。按原子百分含量计,该合金化学成分：Al 42-44％,Mn 2.0-4.0％,W 0.5-1.0％,B 0.1-0.3％,余量为Ti。为保证合金具有在700～750℃具有更高的拉伸强度,热处理制度为：1245-1280℃固溶0.5-1小时,空冷；再经过760-800℃保温3小时时效处理。通过控制合金中O含量,使合金热锻变形后室温拉伸延伸率可达1.72％,通过添加W,控制Al、Mn含量,使合金在800℃具有优异的高温抗氧化性。本发明合金的热变形能力、高温抗氧化性和组织热稳定性均优于国外的Ti-42Al-5Mn合金。(The invention discloses a high-oxidation-resistance and high-plasticity deformed TiAl-based alloy, and belongs to the technical field of TiAl-based alloys. The alloy comprises the following chemical components in percentage by atom: 42 to 44 percent of Al, 2.0 to 4.0 percent of Mn, 0.5 to 1.0 percent of W, 0.1 to 0.3 percent of B and the balance of Ti. In order to ensure that the alloy has higher tensile strength at 700-750 ℃, the heat treatment system is as follows: solid solution is carried out for 0.5-1 hour at the temperature of 1245 and 1280 ℃, and air cooling is carried out; then the mixture is subjected to ageing treatment at 760 and 800 ℃ for 3 hours. The elongation percentage of the alloy after hot forging deformation at room temperature can reach 1.72% by controlling the content of O in the alloy, and the content of Al and Mn is controlled by adding W, so that the alloy has excellent high-temperature oxidation resistance at 800 ℃. The thermal deformation capability, the high-temperature oxidation resistance and the structure thermal stability of the alloy are all superior to those of foreign Ti-42Al-5Mn alloy.)

1. A high oxidation resistance and high plasticity deformation TiAl-based alloy is characterized in that: the alloy comprises the following chemical components in percentage by atom:

42 to 44 percent of Al, 2.0 to 4.0 percent of Mn, 0.5 to 1.0 percent of W, 0.1 to 0.3 percent of B, and the balance of Ti and inevitable impurities.

2. The high oxidation resistance, high plasticity wrought TiAl-based alloy according to claim 1, wherein: in order to improve the plasticity of the deformed alloy, the oxygen content of O in the alloy is strictly controlled, and the oxygen content in the alloy is less than or equal to 0.07 wt.%.

3. The high oxidation resistant, high plasticity wrought TiAl-based alloy according to claim 1 or 2, wherein: in the chemical components of the alloy, Al accounts for 42.1-43.5 at.%, Mn accounts for 2.5-3.8 at.%, and W accounts for 0.5-0.8 at.%.

4. The high oxidation resistant, high plasticity wrought TiAl-based alloy according to claim 1 or 2, wherein: in the chemical composition of the alloy, B is 0.1 to 0.2 at.%.

5. The process for preparing the high oxidation resistance and high plasticity wrought TiAl-based alloy according to claim 1 or 2, wherein the process comprises the following steps: the process comprises the following steps:

(1) proportioning according to alloy components, and directly smelting into an ingot in a vacuum induction smelting furnace by adopting a CaO crucible;

(2) forging the alloy ingot into a bar with the diameter of 30-60 mm, and then carrying out hot rolling to obtain a bar with the diameter of 10-18 mm;

(3) carrying out heat treatment on the bar obtained after forging in the step (2) or the bar obtained after hot rolling, wherein the heat treatment system is as follows: solid solution is carried out for 0.5-1 hour at the temperature of 1245 and 1280 ℃, and air cooling is carried out; then the mixture is subjected to ageing treatment at 760 and 800 ℃ for 3 hours.

Technical Field

The invention relates to the technical field of TiAl-based alloy, in particular to a TiAl-based alloy with high oxidation resistance and high plasticity and a preparation process thereof, and the alloy can be used as a light high-temperature-resistant structural material for key hot-end components of aviation, aerospace and advanced automobile engines.

Background

The TiAl-based alloy has low density, high elastic modulus, comprehensive performance indexes superior to those of the traditional high-temperature alloy and toughness higher than those of common ceramic materials, shows remarkable application prospect in key hot-end component materials of aviation, aerospace and advanced automobiles, becomes one of important representatives of a new-generation light high-temperature material, and is regarded as a preferred material for high thrust-weight ratio advanced aircraft engine high-pressure gas compressors and low-pressure turbine blades. Among a plurality of TiAl alloys, the deformed TiAl alloy has greatly reduced metallurgical defects and peritectic segregation, and has fine, uniform and compact structure and good room temperature and high temperature strength. Meanwhile, the good thermomechanical processing property can ensure that workpieces in various shapes can be processed by the alloy. Therefore, in recent years, wrought TiAl alloys have become a focus and hot spot of research in the field. At present, typical deformed TiAl comprises Ti-43Al-4Nb-1Mo-0.1B (TNM for short) developed by Germany and Austria, Ti-45Al-8.5Nb (high Nb-TiAl for short) developed by China North science, Ti-42Al-5Mn developed by NIMS in Japan, and the like. Among the wrought alloys, Ti-42Al-5Mn has the best hot workability, can realize the non-sheath and non-isothermal forging deformation with large deformation rate under the atmosphere, has low deformation components and wide application prospect. However, researches show that the alloy has the problems of insufficient oxidation resistance, aging precipitation of Laves harmful phases, low room-temperature plasticity (less than 1.0%) of the wrought alloy and the like when the wrought alloy is in service at the temperature of more than 700 ℃, and becomes an important bottleneck problem in industrial application. In order to utilize the strong effects of stable beta phase, low cost, omega brittle phase precipitation inhibition and the like of Mn element, the development of a novel alloy which can break through the problems existing in TiAl-Mn series alloy above 700 ℃ is necessary.

Disclosure of Invention

The invention aims to provide a high-oxidation-resistance and high-plasticity deformation TiAl-based alloy and a preparation process thereof, and compared with the similar alloy, the alloy has lower thermal deformation resistance in the range of 1100-1300 ℃; the high-temperature oxidation resistance is excellent; after forging deformation, the strength at room temperature is moderate, the plasticity is excellent, and the plasticity exceeds deformation alloys such as TNM, high Nb-TiAl, Ti-42Al-5Mn and the like; the material has good tissue stability, and omega and Laves harmful brittle phases are not precipitated after the aging at the temperature of 750 ℃; has excellent thermal deformation capability and can be used for preparing forgings, bars, plates and the like.

In order to achieve the purpose, the technical scheme adopted by the invention is as follows:

a deformation TiAl-based alloy with high oxidation resistance and high plasticity comprises the following chemical components in percentage by atom: 42 to 44 percent of Al, 2.0 to 4.0 percent of Mn, 0.5 to 1.0 percent of W, 0.1 to 0.3 percent of B, and the balance of Ti and inevitable impurities.

In order to improve the plasticity of the deformed alloy, the oxygen content of O in the alloy is strictly controlled, and the oxygen content in the alloy is less than or equal to 0.07 wt.%.

In the chemical composition of the alloy, the Al element is preferably 42.1-43.5 at.%, the Mn element is preferably 2.5-3.8 at.%, the W element is preferably 0.5-0.8 at.%, and the B element is preferably 0.1-0.2 at.%.

The preparation process of the high-oxidation-resistance and high-plasticity deformed TiAl-based alloy comprises the following steps of:

(1) proportioning according to alloy components, and directly smelting into an ingot in a vacuum induction smelting furnace by adopting a CaO crucible;

(2) forging the alloy ingot into a bar with the diameter of 30-60 mm, and then carrying out hot rolling to obtain a bar with the diameter of 10-18 mm;

(3) in order to ensure that the alloy has higher tensile strength at 700-750 ℃, the forged bar or the hot rolled bar obtained in the step (2) is subjected to heat treatment, wherein the heat treatment system is as follows: solid solution is carried out for 0.5-1 hour at the temperature of 1245 and 1280 ℃, and air cooling is carried out; then the mixture is subjected to ageing treatment at 760 and 800 ℃ for 3 hours.

The alloy of the invention has the following design mechanism:

the W is added into the alloy, the contents of Al and Mn are cooperatively controlled, so that the thermal deformation, oxidation resistance and structural stability of the alloy are ensured, and the Laves brittle phase precipitation in the aging process is inhibited.

The alloy of the invention requires strict control of the O content in the alloy, and the O content is required to be less than or equal to 0.07 wt.%, so as to improve the plasticity of the deformed alloy.

The alloy of the invention requires adding a proper amount of B, the content of B is required to be 0.1-0.3 at.%, and the B is matched with other elements in a proper amount so as to improve the room temperature and high temperature strength of the alloy.

In order to ensure that the alloy has higher tensile strength at 700-750 ℃, the heat treatment system of the deformed alloy is as follows: solid solution is carried out for 0.5-1 h at the temperature of 1245 and 1280 ℃, air cooling is carried out, and then aging treatment is carried out for 3 h at the temperature of 760 and 800 ℃.

The invention has the following advantages and beneficial effects:

1. according to the invention, TiAl alloy components are optimized, the ingot prepared by vacuum induction melting can be subjected to thermal deformation treatment under conventional conditions, Hot Isostatic Pressing (HIP) is not required before the alloy ingot is subjected to thermal deformation, and the processes of forging and rolling are also not required to be sheathed and subjected to isothermal treatment, so that the deformation cost is low, and the material utilization rate is high. The production process has strong practicability, and the material can be produced in large batch.

2. The alloy disclosed by the invention has excellent high-temperature oxidation resistance and tissue thermal stability at 700-750 ℃, the high-temperature oxidation resistance is superior to that of Ti-42Al-5Mn, and no Laves brittle phase is precipitated in the tissue in the long-term aging process.

3. The forging deformation alloy prepared by the invention has moderate strength and excellent plasticity at room temperature and high temperature; the strength and plasticity of the hot-rolled bar alloy at room temperature and 750 ℃ exceed those of deformation alloys such as TNM, high Nb-TiAl, Ti-42Al-5Mn and the like.

Drawings

FIG. 1 shows the surface macroscopic morphology of the alloy of the present invention and the existing Ti-42Al-5Mn alloy after cyclic oxidation at 800 ℃/1h for 100 h; wherein: (a) ti-42Al-5Mn alloy; (b) the alloy of the present invention.

FIG. 2 is an oxidation kinetics curve of the alloy of the present invention and Ti-42Al-5Mn alloy after 100h of cyclic oxidation at 800 deg.C/1 h.

Detailed Description

The present invention will be described in further detail with reference to the accompanying drawings and examples.

The invention provides a high-oxidation-resistance and high-plasticity wrought TiAl alloy, which is alloyed by a vacuum induction melting method in the following embodiments, wherein the alloy components are mixed according to the alloy components in the table 1, and a CaO crucible is adopted in a vacuum induction melting furnaceDirectly smelting into cast ingots. Sampling from an alloy ingot casting to test the temperature of 1100-1300 ℃ and the strain rate of 10s^-1And 0.1s^-1A thermal compression stress-strain curve under conditions; performing 100-cycle oxidation resistance experiments under the oxidation condition of 800 ℃/heat preservation time of 1h to judge the high-temperature oxidation performance of the alloy; forging the alloy cast ingot into a bar with the diameter of 30-60 mm, and hot rolling the bar to obtain a bar with the diameter of about 10-18 mm; sampling from a forged rod and a hot rolled rod, detecting the alloy structure by using SEM, EPMA, EBSD and TEM, and performing a room-temperature and high-temperature tensile test on a stretcher to evaluate the comprehensive mechanical properties of the alloy;

after heat treatment is carried out on the wrought alloy (forged bars and hot rolled bars), the precipitation condition of Laves harmful phases is observed in the long-term aging process of the alloy within the temperature range of 750-800 ℃, and the thermal stability of the service structure of the alloy is evaluated.

Examples 1 to 4:

four batches of alloy ingots were melted in a vacuum induction furnace according to the alloy chemical compositions in table 1, namely, example 1 (first batch, No.1), example 2 (second batch, No.2), example 3 (third batch, No.3) and example 4 (fourth batch, No. 4). Wherein the first and second batches of cast ingots are 20-50 kg centrifugal ingots subjected to vacuum induction and centrifugal casting and used for compression, oxidation experiments and forging deformation; the third and fourth batches of cast ingots are vacuum induction and gravity casting, and are 20-50 kgAnd (5) casting ingots for forging and rolling deformation. The chemical compositions of the two batches of material are shown in table 1.

Cutting series from first batch centrifugal cast ingotThe samples were tested in a Gleeble-3800 thermal simulation tester at 1100 deg.C, 1150 deg.C, 1200 deg.C, 1250 deg.C, 1300 deg.C and a strain rate of 10s^-1And 0.1s^-1The thermal compression stress-strain curves under the conditions and the maximum rheological resistance data of the samples are shown in table 2.

A series of 10mm 5mm experimental samples were taken from the first batch of centrifugal ingots, and were subjected to cyclic oxidation at 800 ℃ and cycled once every 1h, according to the aviation industry standard-test method for oxidation resistance of steel and high temperature alloys (HB52580-2000), the total cycle of oxidation was 100 times (100h), and the oxidation weight gain and the oxide film shedding weight were measured using an electronic balance with an accuracy of 0.1 mg. The macroscopic morphology and the oxidation kinetics of the alloys of the invention after oxidation are shown in FIGS. 1-2. As can be seen from the figure, the oxide film formed on the surface of the new alloy does not fall off at the temperature of 800 ℃, the adhesiveness is good, and the oxidation resistance is excellent.

And forging and deforming the first and second batches of centrifugal cast ingots. The initial deformation temperature of forging is 1300-1350 ℃, and the final deformation temperature is more than 1100 ℃. Adopts a two-upsetting and two-drawing process, and the dimension before forging is as followsThe diameter of the section after forging is 30-50 mm, and the deformation is more than 60%. Samples were taken from the forgings for room, high temperature tensile properties and microhardness testing, and the data are shown in tables 3 and 4.

The third and fourth batchesForging the cast ingot into the section diameter by a primary drawing processThe forging ingot has the forging initial deformation temperature of 1300-1350 ℃ and the final deformation temperature of more than 1100 ℃. Rolling the mixture into a bar with the diameter of 10-18 mm by a Y-shaped rolling mill with one fire and multiple apertures, wherein the rolling initial deformation temperature is 1300-1350 ℃. Samples were taken from the rods and tested for room, high temperature tensile testing and the data are given in Table 5.

The heat treatment system of the alloy is solid solution at the temperature of 1245 plus 1280 ℃ for 0.5-1 hour, air cooling and then aging treatment at the temperature of 760 plus 800 ℃ for 3 hours. Table 6 lists the room, high temperature tensile properties data for the new alloys after heat treatment in the as-forged and as-rolled state.

Table 7 sets forth the corresponding instantaneous tensile strength data for the alloys of the invention and the Ti-42Al-5Mn alloy after 30 days aging at 800 ℃. As can be seen from the data in the table, the alloy of the invention has good performance stability, which is obviously superior to Ti-42Al-5Mn alloy.

TABLE 1 four batches of the alloy chemistry of the invention (at.%) smelted in a vacuum induction furnace

TABLE 2 maximum rheological stress (MPa) at different temperatures (DEG C) for the alloy of the invention and Ti-42Al-5Mn alloy

TABLE 3 wrought alloy of the present invention and Ti-42Al-5Mn instantaneous tensile Properties at Room temperature and high temperature

TABLE 4 wrought alloy of the present invention and Ti-42Al-5Mn microhardness

TABLE 5 instantaneous tensile Properties at Room temperature and elevated temperature of the alloys according to the invention for different sizes of rolled bars

TABLE 6 instantaneous tensile Properties at Room temperature and high temperature of the alloys according to the invention after Heat treatment

TABLE 7 instantaneous tensile Properties at room temperature of the alloys of the invention and of the Ti-42Al-5Mn alloy after long term aging