Achieving grain refinement and ultrahigh yield strength in laser aided additive manufacturing of Ti−6Al−4V alloy by trace Ni addition
Shang Sui, Youxiang Chew, Fei Weng, Chaolin Tan, Zhenglin Du, Guijun Bi
Abstract
Fabricating fine equiaxed grains without undesirable secondary phases is highly challenging for additively manufactured Ti−6Al−4V alloy. The reference amount of Ni addition, which can achieve grain refinement without secondary phase formation, is 0.9 wt. % based on Thermo-Calc calculation. The Ti−6Al−4V−0.9Ni alloy produced by laser-based directed energy deposition demonstrate refined microstructure and an ultrahigh yield strength (1309 MPa). A modified quantitative model is proposed to analyse the strengthening mechanism, and the results demonstrate that the yield strength increment is mainly ascribed to the refined α phase. This work can contribute to the development of customised titanium alloy using additive manufacturing.