Achieving high strength and ductility in selective laser melting Ti-6Al-4V alloy by laser shock peening

In this work, the influences of laser shock peening (LSP) on the residual stress state, microstructures and mechanical properties of Ti-6Al-4V alloy fabricated by selective laser melting (SLM) were researched. Particularly, the microstructural evolution before and after LSP was clarified using electron backscatter diffraction (EBSD) and transmission electron microscopy (TEM) observations. The results showed that the residual stress was adjusted from tensile to compressive state. Furthermore, high-density dislocations and a great number of parallel nano mechanical twins (nano-MTs) were promoted in the coarse lamellar alpha' structures, contributing to the grain refinement. The ultimate tensile strength and elongation of the SLM-manufactured (SLMed) Ti-6Al-4V alloy increased by approximately 14.3% and 18.3% after LSP treatment, respectively. Finally, the dominant mechanism of tensile property enhancement by LSP was revealed. High levels of compressive residual stress and grain refinement of the alpha' structures induced by LSP realized the excellent combination of strength and ductility. (c) 2021 Elsevier B.V. All rights reserved.

Automated summary

This research investigated the influences of laser shock peening (LSP) on the residual stress state, microstructures, and mechanical properties of Ti-6Al-4V alloy fabricated by selective laser melting (SLM). The results showed that LSP treatment adjusted the residual stress from tensile to compressive state and promoted the formation of high-density dislocations and parallel nano mechanical twins (nano-MTs) in the coarse lamellar alpha' structures, resulting in grain refinement. The ultimate tensile strength and elongation of the SLMed Ti-6Al-4V alloy increased by approximately 14.3% and 18.3% after LSP treatment, respectively. The study revealed that the combination of high levels of compressive residual stress and grain refinement achieved by LSP contributed to the enhancement of both strength and ductility in the alloy.