Preparation and Detection Method for Indirect Tensile Specimens of Hard α Inclusions in Titanium Alloys

Abstract

The present invention relates to the field of titanium alloy material preparation, and specifically relates to a method for preparing and detecting an indirect tensile 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 hot isostatic pressing technology; (2) processing disc-shaped indirect tensile specimens by wire cutting; (3) preparing tensile specimens with a nitrogen content of less than 12 wt%; (4) performing indirect tensile property tests using a high-temperature hot compression testing machine, where the test temperature is 900°C to 1100°C and the strain rate is 0.01S ‑1 ~10S ‑1 . Thus, it is possible to accurately detect the hot deformation characteristic data of TiN materials with different nitrogen contents, break through the key technologies for the preparation and detection of indirect tensile specimens of TiN inclusion materials, and solve the "bottleneck" problem of China's independent airworthiness system.

Description

Technical Field

[0001] The present invention relates to the field of titanium alloy material preparation, and particularly relates to a preparation and detection method for an indirect tensile 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 caused by the fatigue fracture of the disk due to 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, in combination with the content of Article 33.70 of the airworthiness regulations for aero-engines, the first thing is to obtain the thermal deformation characteristic data of TiN inclusion materials. However, the domestic accumulation of this data is blank, so it is urgent to carry out TiN material thermal 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 thermal deformation characteristic data of TiN materials under China's industrial system has become a "stuck neck" problem in 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 an indirect tensile 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 indirect tensile 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 an indirect tensile specimen of a medium-hard α inclusion material in titanium alloy, comprising the following steps:

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

[0007] (2) Processing a disc-shaped indirect tensile specimen by wire cutting, with the diameter of the specimen being 9.5mm and the thickness being 3.2mm.

[0008] (3) First, use a speed-adjustable grinding machine with a grinding head to grind the surface of the indirect tensile specimen to remove the oxide layer, then perform corrosion treatment with a solution of hydrofluoric acid, nitric acid, hydrochloric acid and water in a volume ratio of 1-2:5-7:≤1:7, then perform fine grinding treatment with 2000# water sandpaper, and finally perform dehydrogenation heat treatment on the treated specimen in a vacuum heat treatment furnace at 450°C ± 20°C for 2-4h, so as to prepare an indirect tensile specimen with a nitrogen content below 12wt%.

[0009] (4) Vertically arrange a disc-shaped indirect tensile specimen between the fixtures of the indirect tensile test device, apply a pressure F to the indirect tensile specimen through the fixtures, and use a high-temperature hot compression testing machine to perform indirect tensile property testing, with the test temperature being 900°C - 1100°C and the strain rate being 1S -1 ~10S -1 .

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

[0011] In the method for preparing and detecting an indirect tensile specimen of a medium-hard α inclusion material in titanium alloy, in step (3), the concentrations of hydrofluoric acid, nitric acid and hydrochloric acid are 35wt% - 40wt%, 65wt% - 68wt% and 33wt% - 39wt% respectively.

[0012] In the method for preparing and detecting an indirect tensile specimen of a medium-hard α inclusion material in titanium alloy, in step (4), the compressive strength of the indirect tensile specimen is 60 - 100MPa.

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

[0014] In view of the problem that indirect tensile specimens of TiN materials cannot be prepared, the present invention first proposes a method of combining wire cutting, chemical etching and manual polishing to prepare indirect tensile specimens of TiN materials with different nitrogen contents. Through the above method, the preparation of indirect tensile specimens of TiN materials with different nitrogen contents can be realized, solving the problem that indirect tensile specimens of TiN materials cannot be prepared at the present stage, thereby obtaining accurate indirect tensile property data of TiN materials, filling the domestic technical blank in this regard, 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 as follows:

[0016] (1) The operation of the present invention is simple, and indirect tensile specimens of TiN materials can be prepared quickly and with high quality.

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

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

[0019] (4) The present invention obtains indirect tensile property data of TiN materials with different nitrogen contents for the first time in China, filling the domestic data blank in this regard. Description of the Drawings

[0020] Figure 1 It is a schematic diagram of an indirect tensile test device. In the figure, 1 is a fixture and 2 is an indirect tensile specimen. Specific Embodiments

[0021] In the specific implementation process, the preparation and detection method of the indirect tensile specimen of the titanium alloy medium-hard α inclusion material in the present invention includes the following steps: (1) Using hot isostatic pressing technology to prepare TiN inclusion bulk materials with different nitrogen contents; (2) Processing disc-shaped indirect tensile specimens by wire cutting; (3) First, use a speed-controlled grinding machine with a grinding head to grind the surface of the indirect tensile specimen to remove the oxide layer, and then use a solution with a volume ratio of hydrofluoric acid, nitric acid, hydrochloric acid and water of 1-2:5-7:≤1:7 for corrosion treatment, then use 2000# water sandpaper for fine grinding treatment, and finally use a vacuum heat treatment furnace to perform dehydrogenation heat treatment on the treated specimen at 450°C ± 20°C for 2-4 h, thereby preparing an indirect tensile specimen with a nitrogen content of less than 12 wt%; (4) Using a high-temperature hot compression testing machine ( Figure 1 ) to conduct indirect tensile property tests, the test temperature is 900°C to 1100°C, and the strain rate is 0.01S -1 ~10S -1 .

[0022] Such asFigure 1 As shown, a disk-shaped indirect tensile specimen 2 is vertically arranged between the fixtures 1 of the indirect tensile test device, and pressure is applied to the indirect tensile specimen 2 through the fixtures 1.

[0023] Next, the present invention will be further elaborated in detail through embodiments.

[0024] Embodiment 1:

[0025] In this embodiment, a method for preparing and detecting an indirect tensile specimen of a TiN material with a nitrogen content of 2 wt% includes the following steps:

[0026] (1) Using hot isostatic pressing technology to prepare TiN inclusion bulk materials with different nitrogen contents, and the nitrogen content is 2 wt%;

[0027] (2) Processing the indirect tensile specimen by wire cutting. The diameter of the specimen is 9.5 mm, the thickness is 3.2 mm, and the machining allowance is 0.5 mm;

[0028] (3) Using a speed-controlled grinding machine with a grinding head to polish the surface of the indirect tensile specimen to remove the oxide layer;

[0029] (4) Performing corrosion treatment with a solution having a volume ratio of hydrofluoric acid, nitric acid, and water of 1:5:7, and the concentrations of hydrofluoric acid and nitric acid are 35 wt% and 68 wt% respectively;

[0030] (5) Performing fine grinding treatment with 2000# water sandpaper, and then performing dehydrogenation heat treatment on the treated specimen in a vacuum heat treatment furnace at 450 °C for 2 h to prepare an indirect tensile specimen with a nitrogen content of 2 wt%;

[0031] (6) Using a high-temperature hot compression testing machine to perform indirect tensile property testing. The testing temperature is 967 °C, the strain rate is 1S -1 , and the compressive strength is 61 MPa.

[0032] In this embodiment, the thermal deformation characteristic data of the TiN material with a nitrogen content of 2 wt% can be accurately detected, the key technologies for the preparation and detection of the indirect tensile specimen of the TiN inclusion material 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] Embodiment 2:

[0034] In this embodiment, a method for preparing and detecting an indirect tensile specimen of a TiN material with a nitrogen content of 5 wt% includes the following steps:

[0035] (1) Using hot isostatic pressing technology to prepare TiN inclusion bulk materials with different nitrogen contents, and the nitrogen content is 5 wt%;

[0036] (2) The indirect tensile specimens are processed by wire cutting. The diameter of the specimens is 9.5 mm, the thickness is 3.2 mm, and the machining allowance is 0.4 mm;

[0037] (3) First, use a speed-controlled grinding machine with a grinding head to grind the surface of the indirect tensile specimens to remove the oxide layer;

[0038] (4) Subsequently, perform corrosion treatment on the indirect tensile specimens with a solution of hydrofluoric acid, nitric acid, hydrochloric acid, and water in a volume ratio of 2:6:1:7. The concentrations of hydrofluoric acid, nitric acid, and hydrochloric acid are 40 wt%, 65 wt%, and 35 wt% respectively;

[0039] (5) Perform fine grinding with 2000# water sandpaper, and then use a vacuum heat treatment furnace to perform dehydrogenation heat treatment on the treated specimens at 460 °C for 3 h, so as to prepare indirect tensile specimens with a nitrogen content of 5 wt%;

[0040] (6) Use a high-temperature hot compression testing machine to perform indirect tensile property testing. The testing temperature is 948 °C, the strain rate is 3S -1 , and the compressive strength is 65 MPa.

[0041] In this embodiment, the thermal deformation characteristic data of TiN materials with a nitrogen content of 5 wt% can be accurately detected, the key technologies for the preparation and detection of indirect tensile specimens of TiN inclusion materials 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.

[0042] Example 3:

[0043] In this embodiment, a method for preparing and detecting tensile specimens of TiN materials with a nitrogen content of 12 wt% includes the following steps:

[0044] (1) Use hot isostatic pressing technology to prepare TiN inclusion bulk materials with different nitrogen contents, and the nitrogen content is 12 wt%;

[0045] (2) The indirect tensile specimens are processed by wire cutting. The diameter of the specimens is 9.5 mm, the thickness is 3.2 mm, and the machining allowance is 0.3 mm;

[0046] (3) First, use a speed-controlled grinding machine with a grinding head to grind the surface of the indirect tensile specimens to remove the oxide layer;

[0047] (4) Subsequently, perform corrosion treatment on the indirect tensile specimens with a solution of hydrofluoric acid, nitric acid, hydrochloric acid, and water in a volume ratio of 2:7:0.5:7. The concentrations of hydrofluoric acid, nitric acid, and hydrochloric acid are 38 wt%, 67 wt%, and 34 wt% respectively;

[0048] (5) Finish the fine grinding process with 2000# water sandpaper, and then perform dehydrogenation heat treatment on the treated sample in a vacuum heat treatment furnace at 450 °C for 4 h to prepare an indirect tensile sample with a nitrogen content of 12 wt%.

[0049] (6) Use a high-temperature hot compression testing machine to conduct indirect tensile property tests. The test temperature is 971 °C, and the strain rate is 10S -1 , and the compressive strength is 93 MPa.

[0050] In this embodiment, the thermal deformation characteristic data of TiN materials with a nitrogen content of 12 wt% can be accurately detected, breaking through the key technologies for the preparation and detection of indirect tensile samples of TiN inclusion materials, filling the domestic gap in this data, and solving the "bottleneck" problem of China's independent airworthiness system.

[0051] In addition, as described above, it is only a partial representation of the embodiments in the present invention and cannot limit the scope of the rights of the present invention. For researchers in the field, the ratio of the sandpaper grit size, hydrofluoric acid, nitric acid, hydrochloric acid, and water can be adjusted accordingly according to the surface state (surface roughness) of the sample 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 sample. Therefore, making various other corresponding changes and deformations according to the technical solutions and ideas of the present invention still fall within the protection scope covered by the present invention.

Claims

1. A preparation and detection method for an indirect tensile specimen of a medium-hard α inclusion material in a titanium alloy, characterized in that, It includes the following steps: (1) Prepare TiN inclusion bulk materials with different nitrogen contents by hot isostatic pressing technology, where the nitrogen content is below 12 wt%. (2) Process disc-shaped indirect tensile specimens by wire cutting. The diameter of the specimen is 9.5 mm and the thickness is 3.2 mm. (3) First, use a speed-controlled grinding machine with a grinding head to grind the surface of the indirect tensile specimen to remove the oxide layer. Subsequently, perform corrosion treatment with a solution with a volume ratio of hydrofluoric acid, nitric acid, hydrochloric acid, and water of 1 - 2:5 - 7:0.5 - 1:

7. Then, perform fine grinding with 2000# water sandpaper. Finally, perform dehydrogenation heat treatment on the treated specimen in a vacuum heat treatment furnace at 450 °C ± 20 °C for 2 - 4 h to prepare an indirect tensile specimen with a nitrogen content below 12 wt%. (4) A disc-shaped indirect tensile specimen is vertically arranged between the fixtures of the indirect tensile test device, and a pressure F is applied to the indirect tensile specimen through the fixtures. The indirect tensile property test is carried out by using a high-temperature hot compression testing machine. The test temperature is 900°C to 1100°C, and the strain rate is 1S -1 ~10S -1 . The compressive strength of the indirect tensile specimen is 60 to 100 MPa.

2. The preparation and detection method of the indirect tensile 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 indirect tensile specimen of the medium-hard α inclusion material in the titanium alloy according to claim 1, characterized in that, In step (3), the concentrations of hydrofluoric acid, nitric acid, and hydrochloric acid are 35 wt% - 40 wt%, 65 wt% - 68 wt%, and 33 wt% - 39 wt% respectively.

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