Effect of heat treatment on the impact toughness and thermal properties of the AlSi10Mg alloy manufactured by laser powder bed fusion

The objective of this work was to investigate the impact toughness and thermal properties of laser powder bed fusion AlSi10Mg alloy under the influence of different heat treatment conditions viz. T6 and direct aging (DA). At room temperature, the tensile results showed that the DA alloy possessed higher yield and ultimate tensile strengths whereas, the T6 alloy had lower yield strength and ultimate tensile strength as expected. Impact energy absorption value of DA alloy was higher than the T6 alloy; however, lower than the as-built condition. Fractographic examination after impact toughness test revealed that crack propagated mainly along the molten pool boundary and high-density precipitated Si particles were also observed inside the fine dimple in DA alloy. Variation in microstructural morphology, cellular structure, and the distribution of Si particles due to heat treatments substantially affected impact toughness and thermal properties. The thermal properties such as heat capacity, thermal diffusivity, and thermal conductivity as a function of different heat treatment conditions were suggested. DA specimen had the lowest thermal conductivity and thermal diffusivity than as-built and T6 specimens. It indicated that heat transfer was hindered by the fine Si particles present in the Al matrix and Si-rich region, owing to the low thermal conductivity of Si. Based on the above results, the controlling method for toughness and thermal conductivity of selective laser melted AlSi10Mg alloy was also discussed.