Microscopic simulation of stacking fault energy and mechanical properties in CrCoNiAlxTiy high-entropy alloys†

CrCoNi-based high-entropy alloys(HEAs) have garnered increasing attention due to their superior strength, wear resistance, plasticity, and toughness. However, how to simultaneously optimize strength and plasticity, especially under cryogenic conditions, remains a challenging materials design problem. Microscopic simulations are essential for understanding stacking fault properties and mechanical properties of HEAs by modeling their complex microstructures. This study focuses on CrCoNiAl_xTi_y HEAs, analyzing their plasticity–toughness balance using molecular dynamics (MD) simulation and density functional theory (DFT) calculation. The effects of Al and Ti doping on microstructure, stacking fault energy (SFE) and Young's modulus were investigated, respectively. Results indicate high Ti content decreases SFE and Young's modulus while enhancing the material's plastic toughness, whereas high Al content tends to increase the SFE and also reduce the Young's modulus, collectively influencing the mechanical properties of CrCoNiAl_xTi_y HEAs. Stress–strain analysis at different temperatures reveals improved mechanical properties at low temperatures. In addition, Machine Learning (ML) results show that the XGBT model best estimates the mechanical properties of HEAs, with the resulting R² closest to 1 and the smallest RMSE. This work offers a mechanistic understanding of composition-dependent deformation behavior in HEAs and provides theoretical guidance for alloy design in extreme environments such as aerospace and polar applications.