Development of high strength Aluminum-based alloys for Laser Powder Bed Fusion

Promovendus/a: Guichuan Li

Promotor(en): Prof. dr. ir. Kim Vanmeensel

Most Aluminum-based alloys currently investigated in Additive Manufacturing (AM) using the Laser Powder Bed Fusion (L-PBF) technique are directly adopted from those developed for the conventional cast and post-thermomechanical processes but are not optimized for L-PBF processing. For instance, high strength Al alloys, such as Al-Cu-Mg and Al-Zn-Mg-Cu alloys, are prone to hot cracking during L-PBF, leading to premature failure in the final parts. The processable Al alloys, such as AlSi10Mg and AlSi12 alloys, show unsatisfactory mechanical performance for structural applications in automotive and aerospace industries. The objective of this PhD work was to develop new high strength Al-based alloys tailored for L-PBF with good processability and enhanced static mechanical properties, comparable to or surpassing the wrought AA7075-T6 alloy. The present thesis uses CALPHAD (CALculation of PHAse Diagrams) -based computational thermodynamic tools to guide alloy design so that desired phases, resulting in improved mechanical performance and reduced hot cracking susceptibility compared to the AA2024 and AA7075 alloys, are achieved. Three main approaches are adopted to develop and tailor high strength Al-based alloys for L-PBF: (Ⅰ) improving the L-PBF printability of conventionally used heat-treatable high strength Al-based alloys (AA2024 and AA7075), by mitigating the hot cracking problem via eutectic modification or grain refinement; (Ⅱ) enhancing the static mechanical properties at room temperature and elevated temperatures of printable cast Al-Si-based alloys by alloying with copper (Cu); (Ⅲ) developing new high strength printable Al-Mn-Mg-based alloys taking advantages of the rapid potential of L-PBF. The present thesis demonstrates a successful methodology to tailor the alloy composition to develop high strength lightweight Al-based alloys with good processability using AM processes involving a rapid solidification step.