Preparation and Detection Method for Compression Specimens of Hard α Inclusions in Titanium Alloy

Abstract

The present invention relates to the field of titanium alloy material preparation, and particularly to a method for preparing and detecting a compression 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) machining cylindrical compression specimens by wire cutting; (3) preparing compression specimens with a nitrogen content of less than 12 wt%; (4) performing compression property tests using a high-temperature 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 TiN inclusion material compression specimens, 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 method for preparing and detecting a compression 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, and non-magnetism, and have been widely used in industries such as aerospace, automotive, and energy. Titanium alloys are usually prepared into 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 large limitations. In 1989, a DC10 airliner crashed in Sioux City, Iowa, USA. The crash was caused by 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. 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, first of all, it is necessary to obtain the hot deformation characteristic data of TiN inclusion materials. However, the domestic accumulation of this data is in a blank state, so it is urgent to carry out hot deformation characteristic tests on TiN materials. 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 compression specimen of a medium-hard α inclusion material in a 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 compression 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 compression specimen of a medium-hard α inclusion material in a 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 12 wt%.

[0007] (2) Processing cylindrical compression specimens by wire cutting, with the diameter of the specimen being 4 mm and the height being 6 mm;

[0008] (3) First, use a speed-adjustable grinding machine with a grinding head to polish the surface of the plate-shaped compression specimen to remove the oxide layer, and then perform corrosion treatment with a solution with a volume ratio of hydrofluoric acid, nitric acid, and water of 0.5 - 1.5:3 - 7:6;

[0009] (4) Perform fine grinding treatment with 2000# water sandpaper, and use a vacuum heat treatment furnace to perform dehydrogenation heat treatment on the treated specimen at 500°C ± 20°C for 1 - 2 h, so as to prepare a compression specimen with a nitrogen content below 12 wt%;

[0010] (5) Apply pressure F to the upper and lower surfaces of the cylindrical compression specimen through a fixture, and use a high-temperature compression testing machine to perform compression performance testing, with the testing temperature being 900°C - 1100°C and the strain rate being 0.01S -1 ~1S -1 .

[0011] In the method for preparing and detecting a compression specimen of a medium-hard α inclusion material in a titanium alloy, in step (2), the machining allowance of the specimen is 0.3 - 0.5 mm.

[0012] In the method for preparing and detecting a compression specimen of a medium-hard α inclusion material in a titanium alloy, in step (3), the concentrations of hydrofluoric acid and nitric acid are 35 wt% - 40 wt% and 65 wt% - 68 wt% respectively.

[0013] In the method for preparing and detecting a compression specimen of a medium-hard α inclusion material in a titanium alloy, in step (4), the compressive strength of the cylindrical compression specimen is 180 - 610 MPa.

[0014] The design concept of the present invention is:

[0015] In view of the problem that compression specimens of TiN materials cannot be prepared, the present invention first proposes a method combining wire cutting, chemical etching and manual polishing to prepare compression specimens of TiN materials with different nitrogen contents. Through the above method, the preparation of compression specimens of TiN materials with different nitrogen contents can be realized, solving the problem that compression specimens of TiN materials cannot be prepared at the present stage, thereby obtaining accurate compression 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.

[0016] The advantages and beneficial effects of the present invention are as follows:

[0017] (1) The operation of the present invention is simple, and compression specimens of TiN materials can be prepared quickly and with high quality.

[0018] (2) The present invention has a wide range of applications and can prepare compression specimens of TiN materials with different nitrogen contents.

[0019] (3) The present invention establishes a preparation method for compression specimens of TiN materials with different nitrogen contents for the first time in China.

[0020] (4) The present invention obtains compression 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

[0021] Figure 1 It is a schematic diagram of the compression specimen. Detailed Embodiments

[0022] In the specific implementation process, the preparation and detection method of the compression specimen of the hard α inclusion material in the titanium alloy of 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 cylindrical compression specimens by wire cutting; (3) First, using a speed-adjustable grinding machine with a grinding head to grind the surface of the plate-shaped compression specimen to remove the oxide layer, and then performing corrosion treatment with a solution with a volume ratio of hydrofluoric acid, nitric acid and water of 0.5-1.5:3-7:6; (4) Performing fine grinding treatment with 2000# water sandpaper, and performing dehydrogenation heat treatment on the treated specimen in a vacuum heat treatment furnace at 500°C ± 20°C for 1-2 h to prepare a compression specimen with a nitrogen content of less than 12 wt%; (5) Using a high-temperature compression testing machine to perform compression property testing, the testing temperature is 900°C-1100°C, and the strain rate is 0.01S -1 ~10S -1 .

[0023] As Figure 1 shown, the structure of the compression specimen is cylindrical, the diameter of the specimen is 4 mm, and the height is 6 mm.

[0024] Next, the present invention will be further elaborated in detail through examples.

[0025] Example 1:

[0026] In this example, a method for preparing and detecting a compression specimen of a TiN material with a nitrogen content of 2 wt% includes the following steps:

[0027] (1) Use hot isostatic pressing technology to prepare TiN inclusion bulk materials with different nitrogen contents, and the nitrogen content is 2 wt%;

[0028] (2) Process cylindrical compression specimens by wire cutting. The diameter of the specimen is 4 mm and the height is 6 mm (the machining allowance is 0.5 mm);

[0029] (3) First, use a speed-controlled grinding machine with a grinding head to grind the surface of the plate-shaped compression specimen to remove the oxide layer. Subsequently, perform etching treatment with a solution with a volume ratio of hydrofluoric acid, nitric acid, and water of 0.5:5:6. The concentrations of hydrofluoric acid and nitric acid are 39 wt% and 66 wt% respectively;

[0030] (4) Perform fine grinding treatment with 2000# water sandpaper, and use a vacuum heat treatment furnace to perform dehydrogenation heat treatment on the treated specimen at 500 °C for 1 h, thereby preparing a compression specimen with a nitrogen content of 2 wt%;

[0031] (5) Use a high-temperature compression testing machine to perform compression performance testing. The testing temperature is 976 °C, the strain rate is 0.32S -1 , and the compressive strength is 189 MPa.

[0032] In this example, 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 TiN inclusion material compression specimen are broken through, the domestic blank of this data is filled, and the "bottleneck" problem of China's independent airworthiness system is solved.

[0033] Example 2:

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

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

[0036] (2) Process plate-shaped compression specimens by wire cutting. The diameter of the specimen is 4 mm and the height is 6 mm (the machining allowance is 0.45 mm);

[0037] (3) First, use a speed-adjustable grinding machine with a grinding head to grind the surface of the plate-shaped compression specimen to remove the oxide layer. Subsequently, perform corrosion treatment with a solution of hydrofluoric acid, nitric acid, and water in a volume ratio of 1:3:6. The concentrations of hydrofluoric acid and nitric acid are 37wt% and 68wt% respectively;

[0038] (4) Use 2000# water sandpaper for fine grinding, and use a vacuum heat treatment furnace to perform dehydrogenation heat treatment on the treated specimen at 500 °C for 2 h, thereby preparing a compression specimen with a nitrogen content of 6wt%;

[0039] (5) Use a high-temperature compression testing machine to conduct compression performance tests. The test temperature is 965 °C, and the strain rate is 0.02S -1 , and the compressive strength is 195 MPa.

[0040] In this embodiment, the thermal deformation characteristic data of TiN materials with a nitrogen content of 6wt% can be accurately detected, the key technologies for the preparation and detection of compression 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 the preparation and detection of compression specimens of TiN materials with a nitrogen content of 12wt% includes the following steps:

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

[0044] (2) Use wire cutting to process plate-shaped compression specimens. The diameter of the specimen is 4 mm, and the height is 6 mm (the machining allowance is 0.35 mm);

[0045] (3) First, use a speed-adjustable grinding machine with a grinding head to grind the surface of the plate-shaped compression specimen to remove the oxide layer. Subsequently, perform corrosion treatment with a solution of hydrofluoric acid, nitric acid, and water in a volume ratio of 1.5:7:6. The concentrations of hydrofluoric acid and nitric acid are 40wt% and 66wt% respectively;

[0046] (4) Use 2000# water sandpaper for fine grinding, and use a vacuum heat treatment furnace to perform dehydrogenation heat treatment on the treated specimen at 500 °C for 2 h, thereby preparing a compression specimen with a nitrogen content of 12wt%;

[0047] (5) Use a high-temperature compression testing machine to conduct compression performance tests. The test temperature is 950 °C, and the strain rate is 0.78S -1 , and the compressive strength is 603 MPa.

[0048] In this embodiment, it is possible to accurately detect the thermal deformation characteristic data of the TiN material with a nitrogen content of 12 wt%, break through the key technologies for the preparation and detection of the TiN inclusion material compression specimen, fill the domestic gap in this data, and solve the "bottleneck" problem of China's independent airworthiness system.

[0049] 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, and water can be adjusted accordingly according to the surface state of the specimen (surface roughness) and the TiN material composition (nitrogen content), and an appropriate amount of corrosion inhibitor, surfactant, etc. can be added to achieve the best surface state of the specimen. 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 a compression 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 cylindrical compression specimens by wire cutting, with the specimen diameter being 4 mm and the height being 6 mm; (3) First, use a speed-adjustable grinding machine with a grinding head to grind the surface of the plate-shaped compression specimen to remove the oxide layer, and then perform etching treatment with a solution having a volume ratio of hydrofluoric acid, nitric acid, and water of 0.5 - 1.5:3 - 7:6; (4) Perform fine grinding with 2000# water sandpaper, and perform dehydrogenation heat treatment on the treated specimen in a vacuum heat treatment furnace at 500 °C ± 20 °C for 1 - 2 h to prepare a compression specimen with a nitrogen content below 12 wt%; (5) Apply pressure F to the upper and lower surfaces of the cylindrical compression specimen through a fixture, and use a high-temperature compression testing machine to conduct compression performance tests. The test temperature is 900°C to 1100°C, and the strain rate is 0.01S -1 ~1S -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 titanium alloy medium-hard α inclusion material compression specimen 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 titanium alloy medium-hard α inclusion material compression specimen according to claim 1, characterized in that In step (4), the compressive strength of the cylindrical compression specimen is 180 - 610 MPa.

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