Porosity formation mechanisms, microstructure evolution and mechanical performance of AlMgScZr alloy fabricated by laser powder bed fusion: Effect of hatch distance

The present work studied the effect of the hatch distance, on densification, surface quality, melt pool configu-ration, residual stress, microstructure and mechanical performance of the laser powder bed fusion (LPBF) fabricated AlMgScZr alloy. Four hatch distances, i.e., 60, 80, 100 and 120 mu m, were subjected to investigation and comparison. The sample fabricated with a 60 mu m hatch distance demonstrated a near full relative density of 99.80 %, which was attributed to a favorable compromise between nucleation, growth and outgassing of pore during the LPBF process. The specimen processed with a 120 mu m hatch distance demonstrated a relatively smooth surface with Ra of about 15 mu m owing to the adequate lifetime of the melt and the reduced Plateau-Rayleigh capillary instability. The influence of hatch distance on microhardness was not evident. This work demonstrates that the relative density, surface quality, residual stress, grain size, texture and dislocation densities can be well regulated by optimizing hatch distance.