Microstructures and properties of laser welded TC4 sheet alloy by superplastic forming

The laser welding process of 1 mm thick TC4 titanium alloy sheet was conducted.The results showed that the uniform and good-quality joints were obtained by laser welding with modification welding,and there were no pores and cracks in the joint.The microstructures of fusion zone were mainly consisted ofα'acicular martensite.The microstructures in heat affected zone were divided into coarse grain zone and fine grain zone.The fine grain zone contains more acicularα'martensite,and coarse grain zone was composed of lath-shaped α + acicular α'martensite phases.The microhardness of the joint was gradually increased from base metal to fusion zone which presented the highest microhardness,about 371 HV.The laser welded joints had the equivalent strength to that of the base metal.But the elongation of the joint was slightly lower than that of the base metal.The bending angle of the joints was slightly lower than that of the base metal and the fracture occured in the base metal side.