Selective laser melting of stainless steel and alumina composite: Experimental and simulation studies on processing parameters, microstructure and mechanical properties

Highlights: • Printable alumina/316L composite structures by selective laser melting, product shown improved mechanical properties. • Usage of agglomerate reinforcement particles produced composite with even dispersion after laser melting. • Optical properties, and not thermal, resulted in the increased energy requirement for full melting. • In turn lowers the maximum temperature attainable and hence decreased cooling rate, resulting in coarser cellular dendrites. Metal matrix composites (MMC) find their uses as high performance materials. The selective laser melting (SLM) of a 316L stainless steel and Al₂O₃ MMC is presented in this paper. Agglomerate Al₂O₃ particles had shown to be an adequate powder choice with uniform dispersions in the resultant prints. Relative density, phase, microstructure and mechanical properties of all 1-, 2-, 3-wt% doped products were carefully analyzed. Finite element modeling model was developed to study the associated multi-physics phenomena with high efficiency for process parameter optimization. It is found that the change in SLM temperature profile with Al₂O₃ addition is mainly due to the change in optical properties rather than thermal. Hence, both simulation and experimentation revealed that higher laser energy input is needed for optimized melting. In addition, cellular dendrites were found to coarsen with increasing Al₂O₃ addition due to the decreased cooling rate. With hard particle strengthening effects, all samples showed improved hardness with 3-wt% up to 298 HV and 1-wt% samples showing much improved yielding and tensile stresses of 579 and 662 MPa from 316L. Corresponding microlattice built this way demonstrated a 30 and 23% increase in specific strength and energy absorption from that of 316L too.