Effects of rare earth Nd on microstructure and mechanical properties of laser rapid formed TC4 titanium alloy

The effects of rare earth element Nd on the microstructure and mechanical properties were studied for the TC4 titanium alloy by Laser Rapid Forming (LRF). The results showed that with the increasing of Nd content, the macrostructure of laser formed TC4 changed from prior β columnar crystal to complete β equiaxed crystal, and the primary Widmanstaten α structure was transformed to basket weave α structure. The coarse α laths were gradually increased and tended to gather. At the same time, the volume fraction of α cluster on the grain boundary was increased obviously. With the content of element Nd increasing, the elongation of laser formed TC4 was increased significantly at first, then decreased sharply, while the strength changed a little. The tensile strength was up to 975 MPa and the elongation was enhanced to 9.5% for the laser formed TC4 by HDH with the addition of 0.1%-0.2wt.% Nd and the oxygen content as high as 0.26%, while, achieving the specifications of mechanical properties for forged products.