Review on the Tensile Properties and Strengthening Mechanisms of Additive Manufactured CoCrFeNi-Based High-Entropy Alloys

The advent of high-entropy alloys (HEAs) provides new possibilities for the metallurgical community. CoCrFeNi-based alloys have been widely recognized to demonstrate superior mechanical properties, amongst the high-entropy alloy systems; in particular, they possess an outstanding tensile ductility and work-hardening capacity. Additive manufacturing (AM) uses a layer-by-layer material deposition approach to build parts directly from computer-aided design models, which are capable of producing near-net-shape HEAs with superior mechanical properties, surpassing traditional manufacturing methods that require a time-consuming post-treatment process, such as cutting, milling, and molding. Moreover, the rapid solidification inherent in AM processes induces the formation of high-density dislocations, which are capable of enhancing the mechanical properties of HEAs. This review comprehensively investigates and summarizes the diverse strengthening mechanisms within CoCrFeNi-based alloys produced using AM technologies, with a specific focus on their influence on tensile properties. A correlation is established between the AM processing parameters and the resultant phases and microstructures, as well as the mechanical properties of CoCrFeNi-based HEAs, which provide guidelines to achieve a superior strength–ductility synergy.