Effect of heat treatment and laser shock peening on the microstructures and properties of electron beam welded Ti-6.5Al-1Mo-1V-2Zr joints

The effect of the heat treatment and LSP on the microstructures and properties of EBWed Ti-6.5Al-1Mo-1V-2Zr joint were investigated. The characteristic of microstructures, micro-hardness, tensile properties and fracture morphology of specimens were analyzed. The results show that the microstructure of original EBWed specimen contains columnar grains in the edge and equiaxed grains in the center of the FZ, and a large amount of acicula martensitic α′ precipitated within the grains. The microstructure in the HAZ contains a mixture of equiaxed β grains with acicula martensitic α′ and fiber α phase in it. The grain boundary α phases and secondary α phase precipitates in the FZ and HAZ, and the fiber α phase coarsen in the HAZ after heat treatment. The hardness of the whole welded joint have a little increasing after heat treatment, and the level of the hardness increases largely after LSP treatment. The LSPed specimens exhibit higher strength than that of the heat treatment specimens, and the strength of the LSPed specimen increases slightly with increase of LSP impacts. The dominant crack location and propagation path of EBWed Ti-6.5Al-1Mo-1V-2Zr joint are changed after LSP treatment.