Improvement of work-hardening capability and strength of FeNiCoCr-based high-entropy alloys by modulation of stacking fault energy and precipitation phase

Abstract

Face-centered cubic (FCC) structured FeNiCoCr high-entropy alloys (HEAs) generally demonstrate good plasticity but exhibit relatively low strength. To tackle this challenge, we suggest the following approaches: (1) enhancing work-hardening ability through reducing the stacking fault energy of the alloy system. (2) adjusting the composition of alloying elements to control the formation of precipitation phase, thus fortifying the matrix. Based on the aforementioned perspectives, a series of alloys Fe₂NiCoCr(VN)_x (x=0, 0.3, 0.5, 1.0) was designed by adjusting the Fe element content in FeNiCoCr HEAs, and then adding V and N alloying elements to the alloy. Experimental results show that Fe₂NiCoCr(VN)_0.5 HEAs exhibit high-quality work-hardening ability and strength. The yield strength enhanced from 150 MPa to 250 MPa, while the ultimate tensile strength was enhanced from 540 MPa to 800 MPa. This represents an increase of 66% in yield strength and 48% in ultimate tensile strength, respectively. And plasticity remained stable at 25%, outperforming most as-cast FCC-structured HEAs. The changes in stacking fault energy and the dislocation slip behaviors around the precipitation phase were also calculated by the Molecular Dynamics simulation software Large-scale Atomic/Molecular Massively Parallel Simulator. This study not only reduces costs but also provides insights into the tunability of the mechanical properties of materials through alloying non-equiatomic HEAs.