Microstructure and thermal expansion behavior of Al-50Si synthesized by selective laser melting

As a new preparation technique, selective laser melting (SLM) is applied to fabricate an electronic packaging candidate material, i.e., the Al-50Si alloy. The microstructures of the as-cast and the SLM Al-50Si alloys are investigated. The influences of solid solubility on the coefficient of thermal expansion (CTE) of the as-SLM and the heat-treated alloys are investigated. The primary Si can be significantly modified after SLM processing. Moreover, a CTE peak can be observed for the SLM alloy due to the formation of a supersaturated Al(Si) solid solution, which disappears after heat treatment due to Si precipitation. Furthermore, the relationship and differences between theoretical models and the experimentally determined CTE for the Al-50Si alloy will be discussed.