Uncovering the roles of LaB6-nanoparticle inoculant in the AlSi10Mg alloy fabricated via selective laser melting.

The effects of inoculation treatment with LaB 6 nanoparticles (0–2 wt% additions) on the microstructural evolution and mechanical performance in a selective laser melted AlSi10Mg alloy were comprehensively investigated. The addition of 0.2–0.5 wt% LaB 6 nanoparticles was identified to be optimal to achieve substantial grain refinement, microstructural homogeneity and thus remediation in the mechanical property anisotropy in the AlSi10Mg alloy. The substantial grain refinement was attributed to the coherent Al/LaB 6 interfaces, which facilitated the heterogeneous nucleation of Al on the LaB 6 nanoparticles during solidification. Increasing the LaB 6 addition up to 2 wt% only marginally further refined the equiaxed grains, which can be understood in terms of the concept of nucleation free zone formed in the liquid at front of the growing solid-liquid interfaces. The LaB 6 nanoparticles within the nucleation free zone could not be activated to be nucleants for α-Al. As a result, random orientation relationships between LaB 6 nanoparticles within the nucleation free zone and the Al matrix were determined. Those excessive LaB 6 nanoparticles weakened the melt pool boundaries, and therefore deteriorated the longitudinal ductility of the SLMed AlSi10Mg alloy. [ABSTRACT FROM AUTHOR]