Friction stir welding process and superplastic forming process to achieve uniform superplastic forming of titanium alloy welded joints

A technology of friction stir and welded joints, which is applied in welding equipment, metal processing equipment, manufacturing tools, etc., can solve the problems of inability to show uniform deformation, low superplasticity, and deformation of the base material, and achieve high superplasticity and high elongation rate, reducing the effect of flow stress

Active Publication Date: 2022-08-02
INST OF METAL RESEARCH - CHINESE ACAD OF SCI
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  • Abstract
  • Description
  • Claims
  • Application Information

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Problems solved by technology

Unfortunately, the superplasticity of the lamellar structure is still lower than that of the base material, especially the flow stress of the lamellar structure is higher than that of the base material during deformation, which is about 10-30% higher (Wu et al, Achieving superior low-temperature superplasticity for lamellar microstructure in nugget of afriction stir welded Ti-6Al-4V joint, Scripta Mater.122(2016) 26-30), resulting in little deformation of the weld nugget when superplastic forming of the overall joint , the main deformation occurs in the local area of ​​the base metal, resulting in local severe deformation of the base metal to fracture
Therefore, controlling the conventional parameters of FSW can usually only obtain these two common structures, neither of which can show signs of uniform deformation during the overall superplastic forming of the joint

Method used

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  • Friction stir welding process and superplastic forming process to achieve uniform superplastic forming of titanium alloy welded joints
  • Friction stir welding process and superplastic forming process to achieve uniform superplastic forming of titanium alloy welded joints
  • Friction stir welding process and superplastic forming process to achieve uniform superplastic forming of titanium alloy welded joints

Examples

Experimental program
Comparison scheme
Effect test

Embodiment 1

[0028] FSW welding of 2 mm thick as-rolled annealed Ti-6Al-4V alloy was performed using a tool shoulder diameter of 10 mm and a frustoconical W-15 wt% Re tip. During the welding process, the joint is protected with argon gas and the weld is rapidly cooled, and a water-cooled nickel-based superalloy backing plate is used to obtain high-quality welded joints under the welding parameters of tool speed of 400 rpm and travel speed of 100 mm / min . The joint structure is 20% of the initial α equiaxed grains + the secondary α structure of fine lamellae. The average sheet thickness and aspect ratio of the lamellar secondary α structure were 80 nm and 6:1, respectively. The high-temperature superplastic tensile test shows that when the superplastic temperature is 900 °C, the strain rate is 3 × 10 -4 s -1 When , the maximum elongation of the weld nugget is about 600%, and the elongation and flow stress of the weld nugget and the base metal are equivalent. The entire joint is at 900°C...

Embodiment 2

[0033] FSW was performed on a 2 mm thick as-rolled annealed Ti-6Al-4V alloy. Welding was performed with a W-25wt% Re alloy stirring head with a shoulder diameter of 11 mm, the joint was shielded with argon gas during welding and the weld was rapidly cooled, and the welding was performed at a tool speed of 500 rpm and a travel speed of 150 mm / min Under the parameters, WC-Co backing plate is used to obtain high-quality welded joints. The high-temperature superplastic tensile test shows that when the superplastic temperature is 900 °C, the strain rate is 1 × 10 -4 ~1×10 -3 s -1 When the weld nugget has an elongation of 400% or more, it is almost the same as the flow stress of the base metal, and the flow stress when the strain is 0.1% is 15MPa. The entire joint exhibits uniform superplastic deformation, and the joint organization tends to be consistent after the entire joint is uniformly deformed.

[0034] The tensile curve of the TC4 titanium alloy FSW weld nugget and base m...

Embodiment 3

[0038]FSW was performed using a 2 mm thick as-roll annealed Ti-6Al-4V alloy. Welding was performed with a W-25wt% Re alloy stirring tip with a shoulder diameter of 11 mm, the joint was shielded with argon gas during welding and the weld was rapidly cooled, and the welding was performed at a tool speed of 300 rpm and a travel speed of 50 mm / min Under the parameters, a nickel-based superalloy backing plate is used, and a circulating water-cooling backing plate is used to control the temperature of the welding seam to obtain a high-quality welded joint. . The average sheet thickness and aspect ratio of the lamellar secondary α structure were 100 nm and 6:1, respectively. The integral joint with a weld length of 500mm*width of 500mm is used for high temperature superplastic forming with Ar gas. The superplastic temperature used is 900°C, and the gas pressure is 5-20MPa. After forming, a hemispherical component with a diameter of 400mm is obtained. The wall thickness of the comp...

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Abstract

The invention discloses a friction stir welding process and a superplastic forming process for realizing the overall uniform superplastic forming of a titanium alloy welded joint, and belongs to the technical field of welding and superplastic forming of metal materials. The invention adopts the tool shoulder with smaller diameter, adopts the backing plate with faster thermal conductivity, and performs friction stir welding on Ti-6Al-4V titanium alloy under lower heat input, and the welding nugget is obtained by initial equiaxed α phase + two A mixed structure composed of sub-lamellar α-phase. Under a certain temperature and tensile strain rate, the weld nugget exhibits good superplasticity, and the flow stress is almost the same as that of the base metal; the overall joint has superplasticity, and all areas in the entire joint are uniformly deformed, showing uniform thinning characteristics. After molding, the structure of each area of ​​the joint becomes uniform and similar. The invention can remarkably improve the superplastic performance of the titanium alloy integral welded joint, realize the uniform superplastic forming of the integral joint, and improve the uniformity of the structure and the mechanical properties of the superplastic forming component.

Description

Technical field: [0001] The invention relates to the technical field of welding and superplastic forming of metal materials, in particular to a friction stir welding process and a superplastic forming process for realizing the overall uniform superplastic forming of a titanium alloy welded joint. Background technique: [0002] Large-scale and complex structural parts of titanium alloys for aerospace, such as aircraft wall panels, aero-engine air intake lip, etc., are usually prepared by superplastic forming / diffusion joining technology. However, as the structural parts become larger and larger and the demand for high performance becomes more and more urgent, it is more and more difficult to adapt to the diffusion connection due to the problems of long molding time, low production efficiency, coarse structure of components, and difficulty in determining the welding rate. Requirements for the production of high-performance large structural parts. At present, the combination o...

Claims

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Application Information

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Patent Type & Authority Patents(China)
IPC IPC(8): B23K20/12B23K20/26
CPCB23K20/12B23K20/26
Inventor 吴利辉倪丁瑞马宗义薛鹏肖伯律
Owner INST OF METAL RESEARCH - CHINESE ACAD OF SCI
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