Achieving excellent mechanical properties in a dual-phase FeCrNi medium entropy alloy through athermal transformations and dislocation structures

In this study, a face-centered cubic (FCC) + body-centered cubic (BCC) dual-phase Fe40Cr40Ni20 (at.%) medium-entropy alloy (MEA) with outstanding mechanical properties was developed. Deformation and strain-hardening mechanisms of the MEA were investigated using a transmission electron microscope. In the FCC phase, dislocation slip was the main deformation mechanism, and twinning appeared at the high-stress stage. Dislocation tangle induced by multi-slip positively contributed to the improvement of strain hardening ability. In the BCC phase, deformation mainly depended on dislocation slip, stress-induced martensitic transformation, and twinning. ω particles resulting from martensitic transformation strongly inhibited dislocation motion. Deformation twins and dislocation structures enhanced the strain-hardening ability by reducing the dislocation mean free path. The BCC/FCC interface also contributed to strain hardening ability by hindering the dislocation movement. The combined action of multiple mechanisms led to the high strain-hardening rate of the MEA.