Microstructure and Properties of Laser Additive Repaired Electron Beam Welds in Ti-6Al-4V Alloy

Laser additive repair offers a favourable solution for effectively repairing weld defects owing to its high level of automation and precise control over heat input. Additionally, the inherent local heat treatment provides enhanced flexibility in reducing stress levels for larger components. This work describes the use of laser additive repair technology to correct defects in electron beam welded Ti-6Al-4V alloy. The microstructural evolution and mechanical properties of the base metal (BM), heat affected zone (HAZ) and repaired zone induced by local heat treatment were analysed. The results revealed the formation of a dense metallurgical bond between the repaired zone and the BM. It was observed that the grain growth direction underwent a transition from alternating growth to vertical growth following the repair. After local annealing treatment, the structure underwent coarsening and the crystallographic orientation was uniformly distributed across the BM area, heat affected area and repair area. The grain size increased while the proportion of low angle grain boundaries decreased. A strong texture appeared in the {0001} crystal plane and polar density decreased. The residual stress of the sample was reduced by 21.0% in the sigma(x)-direction and 25.8% in the sigma(y)-direction following annealing treatment, leading to a decrease in microhardness. Both tensile strength and elongation surpassed the forging standards for Ti-6Al-4V alloy.