Microstructure, mechanical properties and thermal stability of a high-strength AlFeCrSi alloy processed by laser powder bed fusion

In this study, we investigate a new AlFeCrSi alloy designed for processing by gas atomization and laser powder bed fusion (LPBF). Optimization of processing parameters was carried out to achieve dense samples (∼99.8 %) and maximum hardness of ∼185 HV 0.5 . The mechanical properties at different temperatures up to 400 °C have been characterized by tensile and compression testing in the as-built condition. At room temperature, the new alloy achieves strength values comparable to Al2024-T3 and close to wrought Al7075-T6, while outperforming the LPBF commercial AlSi10Mg alloy and most newly reported LPBF Al alloys. Furthermore, it retains high mechanical strength up to 400 °C (UTS >150 MPa), surpassing both the same wrought alloys and recently developed LPBF Al alloys. The high strength is mainly associated to the addition of Si to the AlFeCr system, which induces the formation of a dense network of spherical and fine silicide phases (Al 12 (Fe,Cr) 3 )Si (∼20 nm)), instead of detrimental intermetallic Al 13 (Fe,Cr) 2-4 phases. To ensure the only formation of silicides and considering the high cooling rate and the high Si solid solubility in the Al lattice, the alloy formulation requires for a higher Si content than the stoichiometrically necessary. Such extra Si content in solid solution influences the thermal stability and phase evolution at high temperatures. This study paves the way for designing suitable high strength aluminum alloys via LPBF and other additive manufacturing technologies.