Research On Diffusion Bonding Technology Of Titanium Alloy And Titanium-aluminum Alloy

As structural materials, Titanium alloy is widely used in aerospace, shipbuilding, chemical and other industries, because of it’s high specific strength, excellent heat resistance, corrosion resistance and fracture toughness properties, etc. In the practical applications of alloy, it’s inevitable to encounter problems of connecting the same or different materials, so obtaining a good connection process is of a great importance.In this paper, heat treatment process of duplex microstructure of Ti-45Al-8.5Nb alloy was studied. Superplastic uniaxial tensile properties of TA15 titanium alloy were also researched. On this basis, we carried out the diffusion bonding of TA15/ TA15 and TC4/Ti-45Al-8.5Nb, to obtain the best process of difusion bonding. And the research results have certain reference value for engineering applications of titanium alloy and titanium-aluminum alloy.As we could see from heat treatment of high-Nb titanium-aluminum alloy, it could improve the inhomogeneity of the alloy raw tissue after homogenization treatment under 1300 ℃ for 2h. Ideal duplex microstructure could be obtained on the condition of 1330 ℃ for 45min, and lamellar tissue distributs uniformly, with equiaxed y tissue ratio close to 1:1. The average size of colonies diameter approximately was 8 u m. From superplastic uniaxial tensile experiments of titanium alloy, it could be seen that the unidirectional superplastic tensile elongation was biggest under 900 ℃. Perpendicular to the rolling direction was 480%, parallel to the rolling direction was 620%. And the superplastic deformation of parallel to the rolling direction was better than that of perpendicular to the rolling direction. The yield strength of TA15 titanium alloy decreased with increasing temperature. However, the yield strength of perpendicular to the rolling direction was slightly greater than that of parallel to the rolling direction. Temperature had significant effect on the superplastic forming process. When the temperature was about 900 ℃, its overall performance was best.Tensile strengths of each group diffusion bonded joints of TA15/TA15 at room temperature and high temperature were close, and didn’t change proportionally with pressure and time. We got a good connection effect, which achieved the same strength of the base materials. The joints could obtain the best mechanical properties under the conditions of 920℃/1.5MPa/2h, whose tensile strength was 925.33MPa and elongation was 14.33% at room temperature, tensile strength was 616.5MPa and elongation was 24.25% at 500℃. Diffusion bonded joints of TC4/Ti-45Al-8.5Nb using Fe-based amorphous intermediate layer or not all obtained uniform and dense joint organization, achieving metallurgical bonding. At the conditions of 940℃ /120MPa/4h, the joint which connected directly was of tensile strength to 651.33MPa and microhardness to 320Hv, and weld width was small. However, at the same conditions, the joint which used Fe-based amorphous intermediate layer was of tensile strength to 640.67MPa and microhardness to 360Hv, and weld width increased.