Experimental and Molecular Dynamics Simulation Study of Chemical Short-Range Order in CrCoNi Medium-Entropy Alloy Fabricated Using Laser Powder Bed Fusion

Abstract

CrCoNi medium entropy alloy (MEA) fabricated by laser powder bed fusion (LPBF) benefits from its distinctive hierarchical microstructure and has great potential as a structural material. However, while the intriguing chemical short-range order (CSRO) widely exists in high/medium entropy alloys, its formation in the LPBF-built samples still lacks enough understanding. In this study, we verified its existence by fine transmission electron microscopy characterizations and utilized hybrid Monte Carlo/molecular dynamics simulations to investigate the features and effects of CSRO in LPBF-built CrCoNi MEA (AM model). Results showed that the CSRO fraction and the stacking fault energy of the AM model lie between those of the well-annealed and random solid solution counterparts. Among these models, the AM model exhibited the best strain hardening ability due to its highest capability to generate and store sessile dislocations. The results agreed well with existing data and provide guidance to the future development of LPBF-built CrCoNi MEA.