Laser powder bed fusion of crack-free 6061Al alloy using nano-sized TiO2 modified powders

Abstract

Growth of coarse columnar grains during solidification easily leads to hot cracking during laser powder bed fusion (LPBF) of Al alloys. This work offers an alternative route to inhibit the formation of coarse columnar grains during LPBF process. The crack-free 6061Al alloy with a refined microstructure was obtained using nano-sized TiO2 modified feedstock powders. After HIPPing, a nearly defect-free sample was obtained with a fracture elongation of 19.5 ± 0.14%. After artificially peak ageing treatment, the TiO2 modified 6061Al alloy fabricated by LPBF exhibits a tensile strength of 336.1 ± 3.5 MPa and the fracture elongation is still 8.1 ± 0.92%. It is believed that the approaches used in this work are also effective for other LPBF fabrication of low-printability Al alloys.