Enhancing microstructure and mechanical properties of FeNi1.5CrCu0.5 high-entropy alloy through precipitation treatment and cold rolling

This study investigates how precipitation treatment affects the microstructure and mechanical properties of FeNi_1.5CrCu_0.5 high-entropy alloy, focusing on the role of precipitates during deformation. Homogenization followed by precipitation treatment formed Cr-rich precipitates, enhancing mechanical properties. After 80 % cold rolling, the homogenized sample (HR) developed uniform fine shear bands, while the homogenized and precipitated sample (HGR) showed a heterogeneous distribution of fine and coarse shear bands. In the HGR sample, rotational dynamic recrystallization within shear bands produced new strain-free grains during deformation. Mechanical testing indicated that precipitation treatment increased ultimate shear strength from 459 MPa to 488 MPa, the shear yield strength from 340 MPa to 347 MPa, and the Vickers hardness from 134 HV to 171 HV, due to Cr₂₃C₆ precipitates impeding dislocation motion. Following 80 % cold rolling, the HGR sample exhibited slightly lower strength (ultimate shear strength: 526 MPa; shear yield strength: 353 MPa) compared to the HR sample. However, a significantly improvement in ductility was observed, with shear elongation increasing from 10 % to 22 %, driven by strain-free grain formation. These results emphasize the critical role of precipitation treatments and cold deformation in optimizing the microstructure and mechanical properties of high entropy alloys for advanced engineering applications.