Effects of direct aging treatment on microstructure, mechanical properties and residual stress of selective laser melted AlSi10Mg alloy

Direct aging treatment is an important post-processing procedure, yet little research has been done on how it balances the mechanical properties and the stress removal for selective laser melted (SLMed) AlSi10Mg alloys. Here, we proposed a typical direct aging treatment on SLMed AlSi10Mg alloys, and studied the effects on their microstructure, properties and residual stress evolution. The results indi-cate that the as-built microstructure is mainly composed of fine cellular alpha-Al and reticulated Si phases, and some pre-existing precipitates and dislocations are found in these cells. The direct aging treatment promotes the precipitation of nano-scaled Si phases and preserves a network-like Si structure. Therefore, the strength of the peak-aged alloy increases while the ductility decreases. As the aging temperature in-creases from 160 to 200 degrees C, aging hardening behavior was accelerated significantly. Aging at 160 degrees C for 4-9 h removes 32.0%-43.0% of the residual stress, which is attributed to the decomposition of the su-persaturated alpha-Al matrix, the precipitation of the nano-Si phase and the exposure of low-angle grain boundaries (LAGBs). Considering the overal alloy performance obtained, over-aging at 160 degrees C for 4 h is the optimized heat treatment regime. Under this condition, the yield strength (YS), ultimate tensile strength (UTS) and elongation (EL) of the alloy in the transverse and longitudinal direction are 309.5 MPa, 464.4 MPa and 8.3% and 286.4 MPa, 464.9 MPa and 5.1%, respectively.(c) 2022 Published by Elsevier Ltd on behalf of The editorial office of Journal of Materials Science & Technology.

Automated summary

This study investigates the direct aging treatment of selectively laser melted (SLMed) AlSi10Mg alloys and analyzes its effects on microstructure, properties, and residual stress. The results show that direct aging treatment promotes the precipitation of nano-scaled Si phases and preserves a network-like Si structure, resulting in increased strength but decreased ductility. The optimal heat treatment regime is over-aging at 160°C for 4 hours.