Preparation and detection method for a plane strain specimen of a medium-hard α inclusion material in a titanium alloy

Abstract

The present invention relates to the field of titanium alloy material preparation, and particularly relates to a method for preparing and detecting a plane strain specimen of a medium-hard α inclusion material in a titanium alloy. The method comprises the following steps: (1) preparing TiN inclusion bulk materials with different nitrogen contents by using hot isostatic pressing technology; (2) machining a cube plane strain specimen by wire cutting; (3) preparing a plane strain specimen with a nitrogen content of less than 12 wt%; (4) performing plane strain performance testing by using a high-temperature hot compression testing machine, wherein the testing temperature is room temperature and the strain rate is 0.01S ‑1 ~10S ‑1 . Thus, the thermal deformation characteristic data of TiN materials with different nitrogen contents can be accurately detected, the key technologies for preparing and detecting plane strain specimens of TiN inclusion materials can be broken through, and the "bottleneck" problem of China's independent airworthiness system can be solved.

Description

Technical Field

[0001] The present invention relates to the field of titanium alloy material preparation, and particularly relates to a method for preparing and detecting a plane strain specimen of a medium-hard α inclusion material in a titanium alloy. Background Art

[0002] Titanium is known as the "third metal" after steel and aluminum. Titanium and its alloys have good properties, such as high specific strength, excellent corrosion resistance, high temperature resistance, non-magnetism, etc., and have been widely used in industries such as aerospace, automotive, and energy. Titanium alloys are usually prepared for components by hot working forming. Titanium is chemically active and will react with nitrogen in the air during alloy melting and hot working forming to form hard α inclusions. During the use of titanium alloy components, hard α inclusions will become crack sources, shortening the service life of the components and causing significant harm and losses to people's lives and property. TiN inclusions are a very harmful type of hard α inclusion defect in titanium alloys. For titanium alloy components, ultrasonic detection is mainly used to detect internal defects. However, due to the elastic anisotropy of the α phase and the high damping characteristics of the β phase in titanium alloys, and at the same time, the density of TiN inclusions is not much different from that of the titanium matrix and the crystal structure is coherent with the titanium matrix, the accuracy of ultrasonic detection of TiN inclusions is very low and there are great limitations. In 1989, a DC10 airliner crashed in Sioux City, Iowa, USA. The crash was due to the fatigue fracture of the disk caused by TiN inclusions in the titanium alloy first-stage fan disk of the engine. In recent years, with the development of China's aviation technology, China is independently developing a number of civil engines, and these engines are all facing the problem of airworthiness certification. However, at present, the airworthiness technical requirements are essentially matched with the development of the industrial systems and technical routes in Europe and the United States, which has led to the "strangling" of the market access of aviation products from other countries by the European and American systems. This means that if China's civil engines cannot pass the existing form of airworthiness certification and win market access, all previous investments will be in vain. It is necessary to establish China's independent airworthiness system. To establish an independent airworthiness system, it is necessary to carry out research work from the source of airworthiness certification. Therefore, combined with the content of Article 33.70 of the airworthiness regulations for aero engines, the first thing is to obtain the hot deformation characteristic data of TiN inclusion materials. However, the domestic accumulation of this data is blank, and it is urgently necessary to carry out TiN material hot deformation characteristic tests. However, since TiN inclusion materials are a kind of substance that is neither metal nor ceramic, and at the same time they have the characteristics of high hardness and high brittleness, traditional specimen processing methods and detection methods are not applicable to TiN materials. Moreover, there are no corresponding preparation standards and detection standards in China for reference. Therefore, how to accurately obtain the hot deformation characteristic data of TiN materials under China's industrial system has become a "bottleneck" problem for establishing China's independent airworthiness system, and the preparation and detection of TiN inclusion material specimens have become a key technology that urgently needs to be broken through. Summary of the Invention

[0003] In order to overcome the above problems, the object of the present invention is to provide a method for preparing and detecting a plane strain specimen of a medium-hard α inclusion material in titanium alloy, which can accurately detect the thermal deformation characteristic data of TiN materials with different nitrogen contents, break through the key technologies for preparing and detecting plane strain specimens of TiN inclusion materials, fill the domestic gap in this data, and solve the "bottleneck" problem of China's independent airworthiness system.

[0004] The technical solution of the present invention is as follows:

[0005] A method for preparing and detecting a plane strain specimen of a medium-hard α inclusion material in titanium alloy, comprising the following steps:

[0006] (1) Use hot isostatic pressing technology to prepare TiN inclusion bulk materials with different nitrogen contents, and the nitrogen content is below 12wt%.

[0007] (2) Use wire cutting to process a cube plane strain specimen, and the specimen is a cube with a side length of 6.35 mm.

[0008] (3) First, use an automatic grinding and polishing machine to polish the surface of the plane strain specimen to remove the oxide layer, and then use a solution with a volume ratio of hydrofluoric acid, nitric acid and water of 1-2:4-8:10 for corrosion treatment, so as to prepare a plane strain specimen with a nitrogen content below 12wt%.

[0009] (4) The plane strain fixture used includes a pressure head, a base, a first gasket, a second gasket, and a specimen. The base is formed by butt-jointing two symmetrical halves into a columnar groove-shaped structure. A first gasket and a second gasket are arranged up and down in the groove cavity of the base. The first gasket is a cylindrical sheet structure, and the second gasket is formed by two symmetrical halves corresponding to form a strip-shaped gap structure. Clamping blocks are arranged at both ends of the strip-shaped gap structure. The outside of the second gasket matches the groove cavity of the base, and the second gasket is fixed through the clamping blocks and the groove cavity of the base. The specimen is arranged in the strip-shaped gap structure. The pressure head is located above the base and corresponds to the specimen. Use a high-temperature hot compression testing machine to apply a pressure F to the specimen through the lower end of the pressure head; use a high-temperature hot compression testing machine to perform plane strain performance testing, the testing temperature is room temperature, and the strain rate is 0.01S -1 ~3S -1 .

[0010] In the method for preparing and detecting a plane strain specimen of the medium-hard α inclusion material in titanium alloy, in step (2), the machining allowance of the specimen is 0.3-0.5 mm.

[0011] In the method for preparing and detecting a plane strain specimen of the medium-hard α inclusion material in titanium alloy, in step (3), the concentrations of hydrofluoric acid and nitric acid are 35wt%-40wt% and 65wt%-68wt% respectively.

[0012] For the preparation and detection method of the plane strain specimen of the medium-hard α inclusion material in the titanium alloy, in step (4), the compressive strength of the cube specimen is 350-1150 MPa.

[0013] The design concept of the present invention is:

[0014] Aiming at the problem that the plane strain specimen of TiN material cannot be prepared, the present invention first proposes a method combining wire cutting, chemical corrosion and manual polishing to prepare plane strain specimens of TiN materials with different nitrogen contents. Through the above method, the preparation of plane strain specimens of TiN materials with different nitrogen contents can be realized, solving the problem that the plane strain specimens of TiN materials cannot be prepared at the present stage, so as to obtain accurate plane strain performance data of TiN materials, filling the domestic technical gap in this item, and providing reliable data and technical support for the establishment of China's independent airworthiness system.

[0015] The advantages and beneficial effects of the present invention are:

[0016] (1) The operation of the present invention is simple, and the plane strain specimen of TiN material can be prepared quickly and with high quality.

[0017] (2) The present invention has a wide range of applications and can prepare plane strain specimens of TiN materials with different nitrogen contents.

[0018] (3) The present invention establishes for the first time in China a preparation method for plane strain specimens of TiN materials with different nitrogen contents.

[0019] (4) The present invention obtains for the first time in China the plane strain performance data of TiN materials with different nitrogen contents, filling the domestic data gap in this item. Description of the Drawings

[0020] Figure 1 Schematic diagram of the plane strain fixture. In the figure, 1 is the indenter, 2 is the base, 3 is the first gasket, 4 is the second gasket, 5 is the specimen, and 6 is the fixture block.

[0021] Figure 2 Exploded view of the plane strain fixture. Detailed Embodiments

[0022] In the specific implementation process, the preparation and detection method of the plane strain specimen of the hard α inclusion material in the titanium alloy of the present invention comprises the following steps: (1) using hot isostatic pressing technology to prepare TiN inclusion block materials with different nitrogen contents; (2) using wire cutting to process the cubic plane strain specimen; (3) first using an automatic grinding and polishing machine to grind the surface of the plane strain specimen to remove the oxide layer, and then using a solution of hydrofluoric acid, nitric acid and water with a volume ratio of 1 to 2: 4 to 8: 10 for corrosion treatment, thereby preparing a plane strain specimen with a nitrogen content of less than 12wt%; (4) using a high temperature hot compression testing machine to test the plane strain performance, the test temperature is room temperature, and the strain rate is 0.01S -1 ~10S -1 .

[0023] like Figure 1 and Figure 2 As shown, the plane strain fixture mainly includes a pressure head 1, a base 2, a gasket 3, a gasket 4, and a sample 5. The base 2 is a columnar groove structure formed by two symmetrical halves connected together. Gaskets 3 and 4 are arranged in the inner cavity of the groove of the base 2. Gasket 1 3 is a cylindrical sheet structure. Gasket 2 4 is a strip-shaped gap structure formed by two symmetrical halves. Blocks 6 are arranged at both ends of the strip-shaped gap structure. The outer side of gasket 2 4 matches the inner cavity of the groove of the base 2. Gasket 2 4 is fixed by the block 6 and the inner cavity of the groove of the base 2. Sample 5 is arranged in the strip-shaped gap structure. The pressure head 1 is located above the base 2 and corresponds to the sample 5. A high-temperature hot compression testing machine is used to apply pressure F to the sample 5 through the lower end of the pressure head 1.

[0024] Below, the present invention is further described in detail by examples.

[0025] Embodiment 1:

[0026] In this embodiment, the preparation and detection method of the plane strain specimen of TiN material with a nitrogen content of 2wt% includes the following steps:

[0027] (1) TiN inclusion block materials with different nitrogen contents were prepared by hot isostatic pressing technology, with the nitrogen content being 2wt%;

[0028] (2) The plane strain specimen is processed by wire cutting. The specimen is a cube with a side length of 6.35 mm and a machining allowance of 0.5 mm.

[0029] (3) Use an automatic grinding and polishing machine to polish the surface of the plane strain specimen to remove the oxide layer;

[0030] (4) using a solution of hydrofluoric acid, nitric acid and water in a volume ratio of 1:4:10 for corrosion treatment, with the concentrations of hydrofluoric acid and nitric acid being 36wt% and 67wt%, respectively, to prepare a plane strain specimen with a nitrogen content of 2wt%;

[0031] (5) The plane strain performance test was carried out using a high-temperature hot compression testing machine. The test temperature was room temperature and the strain rate was 0.27S -1 , and the compressive strength was 352 MPa.

[0032] In this embodiment, the thermal deformation characteristic data of TiN materials with a nitrogen content of 2 wt% can be accurately detected, the key technologies for the preparation and detection of plane strain specimens of TiN inclusion materials are broken through, the domestic blank of this data is filled, and the "stuck neck" problem of China's independent airworthiness system is solved.

[0033] Example 2:

[0034] In this embodiment, a method for preparing and detecting a plane strain specimen of a TiN material with a nitrogen content of 6 wt% includes the following steps:

[0035] (1) Hot isostatic pressing technology was used to prepare TiN inclusion bulk materials with different nitrogen contents, and the nitrogen content was 6 wt%;

[0036] (2) The plane strain specimen was machined by wire cutting. The specimen was a cube with a side length of 6.35 mm and the machining allowance was 0.3 mm;

[0037] (3) An automatic polishing machine was used to polish the surface of the plane strain specimen to remove the oxide layer;

[0038] (4) Subsequently, corrosion treatment was carried out using a solution with a volume ratio of hydrofluoric acid, nitric acid and water of 2:8:10. The concentrations of hydrofluoric acid and nitric acid were 38 wt% and 66 wt% respectively, so as to prepare a plane strain specimen with a nitrogen content of 6 wt%;

[0039] (5) The plane strain performance test was carried out using a high-temperature hot compression testing machine. The test temperature was room temperature and the strain rate was 0.86S -1 , and the compressive strength was 1116 MPa.

[0040] In this embodiment, the thermal deformation characteristic data of TiN materials with a nitrogen content of 6 wt% can be accurately detected, the key technologies for the preparation and detection of plane strain specimens of TiN inclusion materials are broken through, the domestic blank of this data is filled, and the "stuck neck" problem of China's independent airworthiness system is solved.

[0041] Example 3:

[0042] In this embodiment, a method for preparing and detecting a plane strain specimen of a TiN material with a nitrogen content of 12 wt% includes the following steps:

[0043] (1) Hot isostatic pressing technology was used to prepare TiN inclusion bulk materials with different nitrogen contents, and the nitrogen content was 12 wt%;

[0044] (2) The plane strain specimen is processed by wire cutting. The specimen is a cube with a side length of 6.35 mm, and the machining allowance is 0.4 mm;

[0045] (3) The surface of the plane strain specimen is polished by an automatic grinding and polishing machine to remove the oxide layer;

[0046] (4) The plane strain specimen is corroded with a solution with a volume ratio of hydrofluoric acid, nitric acid and water of 1:7:10. The concentrations of hydrofluoric acid and nitric acid are 37 wt% and 65 wt% respectively, so as to prepare a plane strain specimen with a nitrogen content of 12 wt%;

[0047] (5) The plane strain performance is tested by a high-temperature hot compression testing machine. The test temperature is room temperature, and the strain rate is 0.03S -1 , and the compressive strength is 697 MPa.

[0048] In this embodiment, the thermal deformation characteristic data of the TiN material with a nitrogen content of 12 wt% can be accurately detected, the key technologies for the preparation and detection of the plane strain specimen of the TiN inclusion material are broken through, the blank of this data in China is filled, and the "stuck-neck" problem of China's independent airworthiness system is solved.

[0049] In addition, as mentioned above, only some representatives of the embodiments in the present invention are given, and the scope of the rights of the present invention cannot be limited by this. For researchers in this field, the grit size of the sandpaper, the ratio of hydrofluoric acid, nitric acid and water can be adjusted accordingly according to the surface state of the specimen (surface roughness) and the composition of the TiN material (nitrogen content), and an appropriate amount of corrosion inhibitor, surfactant, etc. can be added to achieve the best surface state of the specimen. Therefore, various other corresponding changes and deformations made according to the technical solutions and technical ideas of the present invention still fall within the protection scope covered by the present invention.

Claims

1. A preparation and detection method for a plane strain specimen of a medium-hard α inclusion material in a titanium alloy, characterized in that, Including the following steps: (1) Using hot isostatic pressing technology to prepare TiN inclusion bulk materials with different nitrogen contents, where the nitrogen content is below 12 wt%; (2) Processing cube plane strain specimens by wire cutting, and the specimens are cubes with a side length of 6.35 mm; (3) First, use an automatic polishing machine to polish the surface of the plane strain specimens to remove the oxide layer, and then use a solution with a volume ratio of hydrofluoric acid, nitric acid, and water of 1 - 2:4 - 8:10 for etching treatment to prepare plane strain specimens with a nitrogen content below 12 wt%; (4) The plane strain fixture adopted includes a pressure head, a base, gasket one, gasket two, and a specimen. The base is formed by butt-jointing two symmetric halves into a columnar groove-shaped structure. Gasket one and gasket two are arranged vertically in the groove cavity of the base. Gasket one is a cylindrical sheet structure, and gasket two is formed by two symmetric halves corresponding to form a strip-shaped gap structure. Clamping blocks are arranged at both ends of the strip-shaped gap structure. The outer side of gasket two matches the groove cavity of the base, and gasket two is fixed through the clamping blocks and the groove cavity of the base. The specimen is arranged in the strip-shaped gap structure. The pressure head is located above the base and corresponds to the specimen. A high-temperature hot compression testing machine is used to apply a pressure F to the specimen through the lower end of the pressure head; a high-temperature hot compression testing machine is used to conduct a plane strain performance test. The test temperature is room temperature, and the strain rate is 0.01S -1 ~3S -1 ; In step (3), the concentrations of hydrofluoric acid and nitric acid are 35 wt% - 40 wt% and 65 wt% - 68 wt% respectively.

2. The preparation and detection method of the plane strain specimen of the titanium alloy medium-hard α inclusion material according to claim 1, characterized in that, In step (2), the machining allowance of the specimen is 0.3 - 0.5 mm.

3. The preparation and detection method of the plane strain specimen of the medium-hard α inclusion material in titanium alloy according to claim 1, characterized in that, In step (4), the compressive strength of the cube specimen is 350 - 1150 MPa.

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