Microstructural evolution in the welding zone of laser shock peened 316L stainless steel tube

Typical microstructure morphologies in the near-surface layer of the welding zone of gas tungsten arc welded 316L stainless steel tube with and without laser shock peening (LSP) were characterized by optical microscopy and transmission electron microscopy observations. Experimental results and analysis indicated that massive LSP treatment has an important influence on microstructures in the welding zone and heat-affected zone of the welded stainless steel tube. Special attention has been paid to the grain refinement mechanism induced by massive LSP treatment is proposed in the near-surface layer of the welding zone, consisting of the formation of dislocation tangles and dislocation walls due to the pile up of dislocation lines, the development and formation of subgrain boundaries, and the evolution from subgrain boundaries to new grain boundaries. Meanwhile, under laser shock wave, the coarse grain in the near-surface layer in heat-affected zone of the welded specimen was also divided by dislocation movement.