Effect of heat treatment on AlSi10Mg alloy fabricated by selective laser melting: Microstructure evolution, mechanical properties and fracture mechanism

Abstract

The present paper systematically investigated the influence of solution and artificial aging heat treatments on the microstructures and mechanical properties of SLM-produced AlSi10Mg alloy parts. Due to the high cooling rate of SLM, an ultrafine eutectic microstructure in the as-built samples is characterized by spherical nano-sized network eutectic Si embedded in the Al matrix, which gives rise to significantly better tensile properties and Vickers micro-hardness. The solubility of Si atom in the Al matrix of as-built SLM samples is calculated to be 8.89at%. With the increase in the solution temperature, the solubility decreases rapidly. The artificial aging causes the further decrease of the solubility of Si atoms in the Al matrix. Upon solution heat treatment, Si atoms are rejected from the supersaturated Al matrix to form small Si particles. With increasing the solution temperature, the size of the Si particles increases, whereas their number decreases. After artificial aging, the Si particles are further coarsened. The variation in size of Si particles has a significant influence on the mechanical properties of the AlSi10Mg samples. The tensile strength decreases from 434.25±10.7MPa for the as-built samples to 168.11±2.4MPa, while the fracture strain remarkably increases from 5.3±0.22% to 23.7±0.84% when the as-built sample is solution-treated at 550°C for 2h. This study indicates that the microstructure and mechanical properties of SLM-processed AlSi10Mg alloy can be tailored by suitable solution and artificial aging heat treatments.