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

Metal matrix composites (MMC) find their uses as high performing 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 modelling model was developed to study the associated multi-physics phenomena with high efficiencies 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.金属基复合材料（MMC）作为高性能材料拥有广阔的应用前景。本文针对316L不锈钢与氧化铝（Al₂O₃）复合的金属基复合材料的选区激光熔化（SLM）成形工艺展开研究。结果表明，团聚态氧化铝颗粒作为复合粉末原料表现出优异的适用性，可在最终成形件中实现均匀分散。研究团队对质量分数分别为1%、2%、3%的掺杂试样的相对密度、物相组成、微观组织及力学性能开展了系统分析。为高效探究多物理场耦合现象以实现工艺参数优化，本文建立了有限元模型。研究发现，添加氧化铝后，选区激光熔化的温度场分布发生改变，其主导因素为材料光学性能的变化，而非热学性能。仿真与实验结果均证实，为获得优化的熔化效果，需提升激光能量输入。此外，随着氧化铝添加量的增加，冷却速率降低，胞状枝晶发生粗化。得益于颗粒强化效应，所有掺杂试样的硬度均得到提升，其中3%质量分数试样的硬度可达298 HV；1%质量分数试样的屈服强度与抗拉强度分别达到579 MPa与662 MPa，性能显著优于纯316L不锈钢。采用该工艺制备的对应微点阵结构，其比强度与能量吸收能力也较纯316L不锈钢分别提升了30%与23%。