Effect of Cu content on hot-crack resistance of Al-Cu-Mg alloys produced by laser powder bed fusion

The lack of high-strength Al alloys that can be processed by laser powder bed fusion (LPBF) without formation of cracks is considered as one of the main issues for a wider diffusion of this technology in many fields. In this study, the effect of Cu content on the hot-crack resistance of Al-Cu-Mg alloys produced by LPBF was investigated. Powder batches with different compositions were produced by mixing pre-alloyed gas-atomised 2024 alloy powder with increasing amounts (4, 6, 8, 10, and 12 wt.%) of Cu particles and then processed by LPBF. Thermodynamic simulation and microstructure investigations showed that the addition of Cu promotes the formation of abundant eutectic phase mixture, refines the grain structure and reduces the solidification temperature range, thus decreasing the solidification cracking susceptibility of the material. Samples produced with more than 10 wt.% of Cu featured relative density higher than 99.5% and no solidification cracks.