Abstract:Single-layer and multilayer laser additive manufacturing (LAM) for TC11 alloy with different Nd additions was conducted and the effect of Nd addition on microstructure and properties was studied. With the addition of Nd, the aspect ratio of melting pools of single-layer specimens increases and the columnar-to-equiaxed transition occurs. The original β grain size and α plate width of TC11-1.0Nd are significantly reduced compared with those of pure TC11 specimens. It is proposed that the evenly distributed fine Nd₂O₃ precipitates of about 1.51 μm are formed preferentially during rapid solidification of melting pool, and they serve as heterogeneous nucleation particles to refine the microstructure in the subsequent solidification and solid-state phase transformation. Due to the multiple effects of Nd on the microstructure, the ultimate tensile strength of TC11-1.0Nd increases, while the yield strength, ductility and microhardness decrease compared with those of pure TC11.

Key words: laser additive manufacturing; titanium alloy; rare-earth element; microstructure; grain refinement; mechanical properties