The T-joints of Ti?6Al?4V alloy were manufactured by double-sided synchronized laser beam welding with the homologous filler wire. The formation, microstructure and mechanical properties of welded joints as well as th...The T-joints of Ti?6Al?4V alloy were manufactured by double-sided synchronized laser beam welding with the homologous filler wire. The formation, microstructure and mechanical properties of welded joints as well as the correlations of each other were investigated. The results indicate that the quality of weld seams is good without defects such as discontinuity, beading, visible cracks or porosity, which is linked to the steady molten pool behavior and droplet transition. The morphologies of the heat affected zone (HAZ) located on the skin and stringer are disparate. The microstructure of the HAZ and fusion zone (FZ) is mainly comprised of acicular martensiticα′ phases. The microhardness of the HAZ and FZ is higher than that of the base metal (BM) and reaches a maximum value at the HAZ near FZ on the stringer. The tensile specimens along the skin and stringer fractured at the BM with ductile fracture surfaces.展开更多
The superplastic forming of Ti alloy welds has great application prospects in producing integrated components. However, the nugget zone（NZ） of the Ti alloy welds,produced by fusion welding or conventional friction s...The superplastic forming of Ti alloy welds has great application prospects in producing integrated components. However, the nugget zone（NZ） of the Ti alloy welds,produced by fusion welding or conventional friction stir welding（FSW）, consists of lamellar micro structure, which exhibits either low superplasticity or high superplastic temperautre and low strain rate. As a result, the NZ plays a leading role in hindering the superplastic forming of the whole welds.In this study, submerged friction stir welding（SFSW） was conducted in Ti-6Al-4 V alloy for the first time, and a defectfree weld with the NZ consisting of a strip microstructure was obtained. The NZ exhibited a low-temperature superplasticity at 600℃, which was the lowest superplastic temperature ever reported in the Ti alloy welds. Besides, at 800℃, the NZ showed high strain rate（3×10^（-2） s^（-1）） superplasticity and a largest elongation of 615% at 1×10^（-3） s^（-1）. Compared to conventional FSW joints, the NZ of SFSW joint exhibited a much lower flow stress and a decrease in optimal superplastic temperature by 100℃. This is mainly attributed to the easy globularization of the strip microstructure, enhancing the ability of grain/phase boundary sliding.展开更多
基金Project supported by Science and Technology on Power Beam Processes Laboratory at Beijing Aeronautical Manufacturing Technology Research Institute,China
文摘The T-joints of Ti?6Al?4V alloy were manufactured by double-sided synchronized laser beam welding with the homologous filler wire. The formation, microstructure and mechanical properties of welded joints as well as the correlations of each other were investigated. The results indicate that the quality of weld seams is good without defects such as discontinuity, beading, visible cracks or porosity, which is linked to the steady molten pool behavior and droplet transition. The morphologies of the heat affected zone (HAZ) located on the skin and stringer are disparate. The microstructure of the HAZ and fusion zone (FZ) is mainly comprised of acicular martensiticα′ phases. The microhardness of the HAZ and FZ is higher than that of the base metal (BM) and reaches a maximum value at the HAZ near FZ on the stringer. The tensile specimens along the skin and stringer fractured at the BM with ductile fracture surfaces.
基金supported by the National Natural Science Foundation of China under Grant(51471171,51601194,and 51331008)
文摘The superplastic forming of Ti alloy welds has great application prospects in producing integrated components. However, the nugget zone（NZ） of the Ti alloy welds,produced by fusion welding or conventional friction stir welding（FSW）, consists of lamellar micro structure, which exhibits either low superplasticity or high superplastic temperautre and low strain rate. As a result, the NZ plays a leading role in hindering the superplastic forming of the whole welds.In this study, submerged friction stir welding（SFSW） was conducted in Ti-6Al-4 V alloy for the first time, and a defectfree weld with the NZ consisting of a strip microstructure was obtained. The NZ exhibited a low-temperature superplasticity at 600℃, which was the lowest superplastic temperature ever reported in the Ti alloy welds. Besides, at 800℃, the NZ showed high strain rate（3×10^（-2） s^（-1）） superplasticity and a largest elongation of 615% at 1×10^（-3） s^（-1）. Compared to conventional FSW joints, the NZ of SFSW joint exhibited a much lower flow stress and a decrease in optimal superplastic temperature by 100℃. This is mainly attributed to the easy globularization of the strip microstructure, enhancing the ability of grain/phase boundary sliding.
