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 (Al0.1CoCrFeNi) 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. A novel strategy of manipulating stacking fault energy by lightweight and cost‐effective Al‐doping is proposed, to overcome the thermal‐stress‐induced cracking behavior which has long been regarded as a tough issue in additive manufacturing (AM) produced metallic parts. This work provides useful guidance for the design of strong, ductile, and crack‐free alloys for future AM techniques.