Selective laser melting of high-strength primary AlSi9Cu3 alloy: Processability, microstructure, and mechanical properties

The present work explores the possibility of employing the selective laser melting technique to produce parts in AlSi9Cu3 alloy. This alloy, currently prepared by high-pressure dye casting and intended for automotive application, may benefit from the refined microstructure commonly induced by additive manufacturing techniques. The process parameters were systematically varied to achieve full density, and the resulting defects were studied. Thereafter, microstructural features were analyzed, revealing that the high cooling rate, induced by the process, caused a large supersaturation of the aluminum matrix and the refinement of the eutectic structure. Again, the precipitation of the reinforcing θ phase provided numerous nucleation sites. These features were found to be related to the mechanical behavior of the SLMed AlSi9Cu3 alloy, which outperformed the conventional casted alloy in terms of elongation to failure and strain hardening rate both in the as-built and heat treated conditions.