Homogenization of an Al alloy processed by laser powder bed fusion in-situ alloying

In-situ alloying is a flexible approach to develop novel alloy compositions via Laser Powder Bed Fusion (LPBF). Mixing dissimilar powders, however, turns out a heterogeneous alloying with elements segregation and unconsolidated powder particles. Therefore, the purpose of this work is twofold. First, this paper describes how the in-situ alloying of AlSi10Mg and Cu powders affects the distribution of mixed elements within the as-built alloy. On the other hand, a post-process homogenization heat-treatment was set up to increase the alloy homogeneity. The presence of Cu inhomogeneities was verified both in single scan tracks and bulk samples. Their origin was traced back to the different thermo-physical properties of starting powders. Consequently, due to the intrinsic hardening effect of Cu, nano-hardness spikes in correspondence with Cu segregations were measured. To homogenize the alloy properties across the material bulk, a homogenization heat-treatment at 515 °C was then conducted. After heat-treating, Cu inhomogeneities and intermetallic θ- Al2Cu phase were dissolved entirely into Al matrix leading to an effective alloy homogenization.