Development of New Al-Ca-Cu-Mn-Zr Alloys for Laser Powder Bed Fusion

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The limited thermal stability of conventional aluminium alloys at elevated temperatures restricts their application in laser powder bed fusion (LPBF). In this study, a novel Al6Ca3Cu1.8Mn0.4Zr (wt.%) alloy was developed for improved thermal stability via stable intermetallic phases. LPBF processing of gas-atomised powder identified a reference processing window at 350 W and a hatch distance of 0.08 mm (~97–122 J·mm−3), enabling fabrication of crack-free samples with relative densities above 99.0%. The as-built microstructure consists of a highly refined cellular structure with a quasi-continuous network of intermetallic phases and nanoscale dispersoids within the α-Al matrix, resulting in a yield strength of 206 ± 15 MPa, an ultimate tensile strength of 312 ± 2 MPa and an elongation of 2.7 ± 0.2%. Annealing (350 °C/3 h) leads to partial fragmentation and spheroidization of intermetallic phases, accompanied by a slight decrease in strength (UTS = 277 ± 10 MPa) and elongation (2.4 ± 0.3%), while fracture remains predominantly ductile. The alloy shows softening resistance: room-temperature hardness remains close to the as-built value after annealing at 250–300 °C, whereas more pronounced softening is observed after annealing at 350–400 °C, with subsequent stabilization during prolonged holding.