A heat treatment method for improving the plasticity and toughness of metastable β titanium alloy

Abstract

The present invention belongs to the field of non-ferrous metal processing, and in particular, relates to a heat treatment method for improving the plasticity and toughness of a metastable β titanium alloy. The steps are as follows: subjecting the metastable β titanium alloy to a solid solution treatment, and then air cooling it to room temperature; loading the sample after the solid solution treatment with a certain pressure for heat preservation and pressure aging treatment, and taking it out and air cooling it to room temperature after a certain period of time; placing the sample after stress aging in an aging furnace again for secondary aging and heat preservation treatment, and then taking it out and air cooling it to room temperature. The present invention obtains a high-strength and toughness titanium alloy with good matching of strength and plasticity by regulating the size, morphology and orientation of the α phase precipitated in the titanium alloy.

Description

Technical Field

[0001] The invention belongs to the field of nonferrous metal processing, and in particular relates to a heat treatment method for improving the plasticity and toughness of a metastable beta titanium alloy. Background Art

[0002] Titanium alloys have become the main structural materials for advanced aircraft and aero-engines due to their excellent comprehensive performance matching, such as high strength, low density and weldability. The development of the new generation of aerospace vehicles towards integration, large-scale and complex structures has prompted the design of structural materials to adopt light metal materials with higher comprehensive performance. Therefore, the research on metastable β titanium alloys with higher strength levels has received more attention. The representative alloys abroad are Ti-5553 (Ti-5Al-5Mo-5V-3Cr) and Ti-55531 (Ti-5Al-5Mo-5V-3Cr-1Zr) alloys, which are improved and designed on the basis of BT22 alloy, and have been widely used in the aerospace field. Many domestic units have also carried out research on metastable β titanium alloys and developed a variety of metastable β titanium alloys, such as TB15, TB17 and Ti-1300 (Ti-4Al-5Mo-5V-6Cr-1Nb) alloys.

[0003] However, with the continuous increase in strength requirements, the plasticity of metastable β titanium alloys is greatly restricted, especially the strength, plasticity and toughness of metastable β titanium alloy forgings are difficult to achieve comprehensive improvement. The matching of strength, plasticity and toughness has become an important issue facing the development of metastable β titanium alloys. Summary of the invention

[0004] 1. Technical issues to be resolved

[0005] The present invention mainly aims at the above problems and proposes a heat treatment method for improving the plasticity and toughness of metastable β titanium alloy, the purpose of which is to solve the problem of poor matching of strength and plasticity of metastable β titanium alloy forging billets / forgings.

[0006] (II) Technical solution

[0007] To achieve the above object, the present invention provides a heat treatment method for improving the plasticity and toughness of a metastable β titanium alloy, comprising:

[0008] The metastable β titanium alloy forged sample is placed in a heating furnace for β single phase solid solution treatment;

[0009] The forged sample of the metastable β titanium alloy after solution treatment is subjected to the first aging treatment by loading stress in an aging furnace;

[0010] The sample after the first aging treatment is put into the aging furnace again for the second aging treatment, and then taken out and cooled to room temperature to obtain a heat-treated metastable β titanium alloy.

[0011] Furthermore, the stress applied to the forged sample of the metastable β titanium alloy after the solid solution treatment is compressive stress.

[0012] Furthermore, the specific steps of performing the solution treatment include: placing the metastable β titanium alloy forged sample at T β Solution treatment is carried out in a heating furnace at +50-100℃ for 1-4h.

[0013] Furthermore, the temperature range T1 of the first aging treatment is 500-550°C, the insulation time is 60-300min, and the compressive stress is 10-120MPa.

[0014] Furthermore, the temperature range T2 for the second aging treatment is T1-40°C to T1+10°C, and the insulation time is 0 to 300 min.

[0015] Furthermore, the alloy phase transition temperature T β It is 790±5℃.

[0016] Furthermore, the temperature of the second aging heat-insulating treatment of the metastable β titanium alloy forged sample is not higher than the aging temperature in the first aging treatment.

[0017] Furthermore, the cooling method in the solution treatment step is air cooling.

[0018] Furthermore, the cooling method in the first aging treatment step is air cooling.

[0019] Furthermore, the cooling method in the second aging treatment step is air cooling.

[0020] (III) Beneficial effects

[0021] The above technical scheme of the present invention has the following advantages: through the heat treatment process of β single-phase region solid solution, primary stress loading aging treatment and secondary ordinary aging treatment, the size and precipitation morphology of the secondary α phase and α cluster are regulated by the β single-phase region solid solution and stress aging process, thereby ensuring that the alloy has good strength; the thickness of the secondary α phase layer is adjusted by the secondary aging process, while the existence of α cluster is still guaranteed, thereby improving the plasticity and toughness of the alloy, while ensuring that the strength is not significantly reduced, and the three work together to effectively improve the comprehensive strength, plasticity and toughness of the metastable β alloy. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 This is a microstructure photograph of the Ti-1300 alloy after stress loading aging heat treatment in the first specific embodiment of the present invention.

[0023] Figure 2 This is a microstructure photograph of the Ti-1300 alloy after secondary aging heat treatment in the first specific embodiment of the present invention.

[0024] Figure 3 This is a microstructure photograph of the Ti-1300 alloy after ordinary solution aging heat treatment in the first specific embodiment of the present invention. DETAILED DESCRIPTION

[0025] In order to enable those skilled in the art to better understand the scheme of the present invention, the technical scheme in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work should fall within the scope of protection of the present invention.

[0026] It should be noted that the terms "first", "second", etc. in the specification and claims of the present invention and the above-mentioned drawings are used to distinguish similar objects, and are not necessarily used to describe a specific order or sequence. It should be understood that the data used in this way can be interchanged where appropriate, so that the embodiments of the present invention described herein can be implemented in an order other than those illustrated or described herein. In addition, the terms "including" and "having" and any variations thereof are intended to cover non-exclusive inclusions, for example, a process, method, system, product or device that includes a series of steps or units is not necessarily limited to those steps or units that are clearly listed, but may include other steps or units that are not clearly listed or inherent to these processes, methods, products or devices.

[0027] Solution treatment refers to a heat treatment process in which the alloy is heated to a high temperature single-phase region and maintained at a constant temperature so that the excess phase is fully dissolved into the solid solution and then rapidly cooled to obtain a supersaturated solid solution.

[0028] Aging treatment refers to the heat treatment process in which metal or alloy workpieces (such as low carbon steel, etc.) are subjected to solution treatment, high temperature quenching or a certain degree of cold working deformation, and then placed at a higher temperature or room temperature to maintain their shape and size, and the properties change over time. Generally speaking, after aging, the hardness and strength increase, while the plastic toughness and internal stress decrease.

[0029] The present invention is further described in detail below in conjunction with the accompanying drawings:

[0030] The method for improving the metastable β titanium alloy forging in this embodiment comprises the following steps:

[0031] Step 1: placing the metastable β titanium alloy forging sample in a heating furnace for β single phase solid solution treatment;

[0032] Step 2: Loading stress on the forged sample of the metastable β titanium alloy after the solid solution treatment in an aging furnace for the first aging treatment;

[0033] Step 3: Place the sample after the first aging treatment into the aging furnace again for a second aging treatment, then take it out and cool it to room temperature to obtain a heat-treated metastable β titanium alloy.

[0034] Specifically, fine secondary a phase and a cluster are obtained through a primary stress aging process, ensuring that the alloy has good strength; the secondary aging process regulates the thickness of the secondary a phase layer on the basis of the primary aging process, which improves the plasticity and toughness of the alloy while ensuring the strength. The two together improve the comprehensive strength, plasticity and toughness of the metastable β titanium alloy.

[0035] In the embodiment of the present invention, the stress applied to the forged sample of the metastable β titanium alloy after solid solution treatment is compressive stress.

[0036] Preferably, the specific steps of performing the solution treatment, the first aging treatment, and the second aging treatment include: placing a Ti-1300 (Ti-4Al-5Mo-5V-6Cr-1Nb) alloy forged sample at T β The Ti-1300 alloy is subjected to single-phase solution treatment in a +50-100℃ heating furnace for 1-4h and then air-cooled; the Ti-1300 alloy after solution treatment is kept at T1 temperature (500-550℃) for 60-300min, and a compressive stress of 10-120MPa is applied simultaneously; after aging treatment, it is air-cooled to room temperature to obtain a secondary α phase lamella with small size and certain orientation; the Ti-1300 alloy after aging treatment is kept at T2 temperature (T1-40℃~T1+10℃) for 0-300min and air-cooled to room temperature, so that the secondary α phase lamella is relatively coarsened, but still retains a certain orientation, and obtains better strength, plasticity and toughness.

[0037] It can be understood that the above embodiment clarifies the relationship between the first aging and second aging process parameters. The first aging heat treatment temperature is selected at T1 temperature (500-550°C), mainly to regulate the size and precipitation morphology of the secondary a phase and a cluster, so that the secondary a phase and a cluster can be well precipitated, and the thickness of the sheet is adjusted to ensure the strength. When the aging temperature is too high or too low, it will cause the secondary a and a cluster to coarsen or precipitate insufficiently, affecting the mechanical properties such as alloy strength; the secondary aging temperature is selected at T2 temperature (T1-40°C~T1+10°C), that is, the temperature of the second aging heat treatment is not higher than the aging temperature in the first aging treatment, in order to regulate the size and precipitation morphology of the secondary a phase region a cluster to improve the plasticity of the alloy.

[0038] Preferably, the alloy phase transition temperature T of the metastable β titanium alloy forged sample is β It is 790±5℃.

[0039] To further reveal the nature of the present invention, the following examples are described in detail. It should be understood that, except for the limitations specifically indicated in the appended claims, the present invention is not limited to the specific conditions or details set forth in these examples.

[0040] Embodiment 1:

[0041] First, the Ti-1300 alloy bar sample was solution treated at a solution temperature of 870°C, and then placed in a warm charging furnace, kept warm for 120 minutes, and air-cooled to room temperature after being taken out of the furnace; then the solution treated sample was placed in a heating furnace at 530-540°C, and simultaneously loaded with a pressure of 70-90MPa, kept warm for 240min, and air-cooled to room temperature after being taken out of the furnace; then the stress aging sample was subjected to a second aging treatment at an aging temperature of 520-530°C, kept warm for 120min, and air-cooled to room temperature after being taken out of the furnace, to obtain a relatively coarsened lamellar α phase with a certain orientation.

[0042]

[0043]

[0044] In summary, and from Figure 1-Figure 3 As shown in the experimental photos, the Ti-1300 alloy obtained in this embodiment has a room temperature tensile strength of 1393 MPa, an elongation of 6%, a cross-sectional shrinkage of 12.73%, and an impact toughness of 29.20 J / cm 2 Compared with the unstressed aging specimen, the present embodiment significantly improves the plasticity and toughness of the alloy.

[0045] Any process or method description described in other ways herein may be understood to represent a module, segment or portion of code that includes one or more executable instructions for implementing the steps of a specific logical function or process, and the scope of the preferred embodiments of the present invention includes additional implementations in which functions may not be performed in the order shown or discussed, including performing functions in a substantially simultaneous manner or in the reverse order depending on the functions involved, which should be understood by technicians in the technical field to which the embodiments of the present invention belong.

[0046] The above is only a preferred embodiment of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the technical principles of the present invention. These improvements and modifications should also be regarded as the scope of protection of the present invention.

Claims

1. A heat treatment method for improving the plasticity and toughness of a metastable β titanium alloy, characterized in that: The following steps are involved: The metastable β titanium alloy forging sample is placed in a heating furnace for β single phase solid solution treatment, and the metastable β titanium alloy is Ti-1300 alloy; The forged sample of the metastable β titanium alloy after solution treatment is subjected to the first aging treatment by loading stress in an aging furnace; The sample after the first aging treatment is put into the aging furnace again for the second aging treatment, and then taken out and cooled to room temperature to obtain a heat-treated metastable β titanium alloy; The stress applied to the forged sample of the metastable β titanium alloy after the solid solution treatment is compressive stress; The specific steps of solution treatment include: placing the metastable β titanium alloy forged sample at T β Solution treatment is carried out in a heating furnace at +50-100℃ for 1-4h; The temperature range T1 for the first aging treatment is 500-550°C, the insulation time is 60-300min, and the compressive stress is 10-120Mpa; The temperature range T2 for the second aging treatment is T1-40°C to T1+10°C, and the insulation time is 0 to 300 minutes.

2. The heat treatment method for improving the plasticity and toughness of metastable β titanium alloy according to claim 1, characterized in that: The alloy phase transition temperature T of the metastable β titanium alloy forging sample β It is 790±5℃.

3. The heat treatment method for improving the plasticity and toughness of a metastable β titanium alloy according to claim 1, characterized in that: The temperature of the second aging heat preservation treatment of the metastable β titanium alloy forged sample is not higher than the aging temperature in the first aging treatment.

4. The heat treatment method for improving the plasticity and toughness of a metastable β titanium alloy according to claim 1, characterized in that: The cooling method in the solution treatment step is air cooling.

5. The heat treatment method for improving the plasticity and toughness of metastable β titanium alloy according to claim 1, characterized in that: The cooling method in the first aging treatment step is air cooling.

6. The heat treatment method for improving the plasticity and toughness of a metastable β titanium alloy according to claim 1, characterized in that: The cooling method in the second aging treatment step is air cooling.

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