Effect of heat treatments on microstructure and mechanical properties of AlSi10Mg alloys fabricated by laser powder bed fusion

This study investigated the microstructures and tensile properties of as-build and heat-treated (including T6, T2, and T6-T2 treatments) AlSi10Mg samples fabricated by laser powder bed fusion (LPBF). The microstructure analysis revealed that the trend of eutectic Al-Si phase distribution along grain boundaries for heat-treated samples was significantly weakened, and the eutectic Al-Si phase was transformed into Si particles which were uniformly distributed in α-Al matrix. For the T6-T2-treated specimens, the Si content in particles was the highest. Meanwhile, the T6 treatment increased the proportion of equiaxed grains on vertical section most significantly. However, in the wake of heat treatments, the average grain size on horizontal section had little change while the average grain size on vertical section was increased. The properties analysis demonstrated that the T6-T2-treated specimens obtained the best elongation and worst strength. Besides, the T6 treatment eliminated the anisotropy of the LPBFed specimens basically and synergistically obtained the best combination of strength and plasticity. The T6 treatment weakened the direction difference to the greatest extent, whereas the T2 treatment minimized the stress concentration. According to the comparative finding, the Si content in particles played an important part in properties. Besides, the relationship among inverse pole figure (IPF) maps, pole figure (PF) maps, the mass fraction and distribution of Si in Al matrix and Si particle, the grain size, kernel average misorientation (KAM), and mechanical properties under different heat treatments was established, which provided a new idea for the selection of heat treatments on LPBFed parts.