On the thermal conductivity of AlSi10Mg and lattice structures made by laser powder bed fusion

The thermal conductivity of AlSi10Mg made by laser powder bed fusion (LPBF), and its modification via heat treatment, has received little attention despite possible applications for heat exchangers and thermo-mechanical components. Here, we show that heat treatment can increase the thermal conductivity of LPBF AlSi10Mg to that of cast material. Our results indicate that post-manufacture annealing eliminates the thermal conductivity anisotropy present in the as-built condition, and enhances the conductivity by close to 30 % in the transverse direction (perpendicular to the LPBF build orientation). A solution heat treatment increases the thermal conductivity further still (36 % compared to the as-built condition), while a T6-like treatment provides the greatest increase (44 % compared to the as-built condition). These improvements are related to the evolution of the AlSi10Mg microstructure, especially the breakdown of the Si cellular structure. Additionally, the thermal conductivities of gyroid lattice structures were examined in the as-built and annealed conditions. Contrary to solid specimens, the lattice structures exhibited almost isotropic thermal conductivity in the as-built condition. Their thermal conductivities were increased by the annealing treatment in proportion to their volume fraction. Our findings contribute to the development of a general design-for-additive-manufacturing (DfAM) framework which will make the best possible use of AM materials and lattice structures for heat transfer components.