Research On The Microstructure And Property Of Ti600 High-temperature Titanium Alloy Electron Beam Welded Joints

As a important tool of human deep space exploration and spacial resource exploitation, launch vehicle’s level of development depends largely on the development of rocket propulsion technology. Reduce the weight of thrust chamber can increase engine’s thrust-weight ratio, and then improve the performance of the engine. Titanium and titanium alloy have superior properties of high specific strength, anti-corrosion and safety, excellent resistance to high and low temperature, non-magnetic, small linear expansion, etc. Especially with the research development of high temperature titanium alloy, its high temperature service performance had reached above 600℃, so high temperature titanium alloy became advanced rocket engine material of first choice. Compared with other type high temperature titanium alloy, the high temperature tensile properties, creep resistance and durable performance of Ti600 titanium alloy is very excellent. At home and abroad, there were more researches on welding and connection process of normal titanium alloy than Ti600 titanium alloy.The microstructure and properties of Ti600 alloy joints welded by electron beam and the factors of buckling deformation of thin plate were investigated in this paper. The results showed that the microstructure of the weld seam was ɑ′ acicular martensite. The microstructure of the heat affected zone was the mixture of fine acicular martensite and the primary ɑ phase. The results of property tests indicated that the hardness distribution of weld joint changed smoothly. The roomtemperature tensile strength of the weld seam is equal to the parent metal. Average bending strength of joints had reached 94% of the parent metal’s bending strength.Average impact toughness had reached 74% of the parent metal’s impact toughness.The performance degradation was main caused by coarse columnar crystal in the weld seam. The joints which had been undergone high temperature loading simulating tests exhibited excellent thermostability, the microstructure and properties of the joints didn’t changed obviously. Welding joints in600℃/150Mpa/50 h, creep resistance was poor, creep elongation is 0.766%,speculating it was related with the massive ɑ phase in the parent metal. The finite element simulation of residual stress distribution showed that high temperature service environment is helpful to decrease peak tensile stress in joints. The buckling deformation of thin plate is sensitive to the boundary condition, if initial transverse bending angle was different, the deformation would different. The welding reinforcement should be considered in the numerical modeling, because it contributed a lot to the deformation.