Dimensional changes induced by precipitation of supersaturated solid solution Si in selectively laser-melted AlSi10Mg alloy during heat treatment

Abstract

To elucidate the growth, a kind of non-reversible dimensional change occurring in heat treatments or long-term services, of AlSi10Mg alloy products fabricated by selective laser melting (SLM), the dimensional and microstructural changes arising from a heat treatment at 423 K for 1800 ks were investigated. In as-built state, there were no Si precipitates in the α-Al cells near the top of the specimen and the concentration of the solid solution Si in the α-Al phase was higher than 1.6 wt%. However, some of the supersaturated solid solution Si in the α-Al phase near the bottom of the specimen precipitated during SLM processing. After the heat treatment, the Si precipitates increased in number and coarsened, and the concentration of the solid solution Si in α-Al cells almost became zero. The linear dimensional change arising from the heat treatment was 0.17%, which was much higher than that of gravity cast AlSi10Mg alloy. This linear dimensional change occurred mainly due to the precipitation of the supersaturated solid solution Si in the α-Al phase. • The concentration of the solid solution Si in an as-built AlSi10Mg alloy was more than 1.6 wt%. • The solid solution Si partially precipitated during SLM processing depending on the positions. • The solid solution Si completely precipitated by a heat treatment at 423 K. • The Si precipitation due to the heat treatment resulted in a linear expansion of 0.17% for the alloy.