Manipulating Stacking Fault Energy to Achieve Crack Inhibition and Superior Strength-Ductility Synergy in an Additively Manufactured High-Entropy Alloy.

Additive manufacturing (AM) is a revolutionary technology that heralds a new era in metal processing, yet the quality of AM-produced parts is inevitably compromised by cracking induced by severe residual stress. In this study, a novel approach is presented to inhibit cracks and enhance the mechanical performances of AM-produced alloys by manipulating stacking fault energy (SFE). A high-entropy alloy (HEA) based on an equimolar FeCoCrNi composition is selected as the prototype material due to the presence of microcracks during laser powder bed fusion (LPBF) AM process. Introducing a small amount (≈2.4 at%) of Al doping can effectively lower SFE and yield the formation of multiscale microstructures that efficiently dissipate thermal stress during LPBF processing. Distinct from the Al-free HEA containing visible microcracks, the Al-doped HEA (Al 0.1 CoCrFeNi) is crack free and demonstrates ≈55% improvement in elongation without compromising tensile strength. Additionally, the lowered SFE enhances the resistance to crack propagation, thereby improving the durability of AM-printed products. By manipulating SFE, the thermal cycle-induced stress during the printing process can be effectively consumed via stacking faults formation, and the proposed strategy offers novel insights into the development of crack-free alloys with superior strength-ductility synergy for intricate structural applications.