The Simulation of Post-Heat Treatment in Selective Laser Melting Additive Manufacturing

Post-heat treatment takes a key role for the enhancement of mechanical properties in selective laser melting (SLM) additive manufacturing (AM) of 6xxx series aluminum alloy. To understand the basic mechanism for changes of mechanical properties in the SLM process and the following post-heat treatment, the finite element model and the precipitate evolution (PE) model of SLM AM were established and combined. Results show that the hardness of the fabricated AM component can reach 91.47 HV at 170 °C for 18.8 h, which is 63.1% higher than the as-fabricated state. The comparison of hardness in as-fabricated AM component with experiments shows the validity of the proposed models. Further work on chemical composition shows that the selection of powder particle can greatly affect the hardness of the fabricated AM component. In the selection of 6xxx series aluminum alloy powder, higher Mg and Si contents in their solubility domains lead to higher generation of Mg2Si nano-size precipitates and then cause higher hardness of AM specimen. After the optimal post-heat treatment, the maximum hardness can exceed 100 HV.