Upgrading the strength-ductility trade-off and wear resistance of Al_0.25CoCrFeNiCu and Al_0.45CoCrFeNiSi_0.45 high-entropy alloys through severe cold rolling process

In the present work, Al_0.25CoCrFeNiCu and Al_0.45CoCrFeNiSi_0.45 high entropy alloys (HEAs) were fabricated by induction melting and then subjected to severe cold rolling (SCR) to induce an ultrafine lamellar microstructure. By using electron back scattered diffraction (EBSD) analysis, the microstructural features of the SCR processed HEAs were determined to be deformation bands, severely pancaked grains, and a refined lamellar microstructure. The intense cold rolling method did not result in phase changes, according to X-ray diffraction (XRD) analysis. The HEAs exhibited a decrease in elongation to fracture due to the development of new grain boundaries and dislocations strengthening effect, although an improvement in strength and microhardness was seen with increasing rolling deformation (reduction in thickness). With a tensile strength of 740 MPa and an elongation of 14%, Al_0.25CoCrFeNiCu showed the best strength-ductility combination, while Al_0.45CoCrFeNiSi_0.45 showed a tensile strength of 890 MPa and ductility of 10%. Furthermore, it was discovered that the SCR process causes the alloys' fracture mechanisms to change from ductile to partially brittle. This was particularly noticeable in the Al_0.45CoCrFeNiSi_0.45 HEA. Lastly, the wear rate of 75% SCR Al_0.45CoCrFeNiSi_0.45 (1.2 ± 0.3 × 10^–5 mm³ N^–1 m^–1) was less than that of 75% SCR Al_0.25CoCrFeNiCu (1.8 ± 0.3 × 10^–5 mm³ N^–1 m^–1). The predominant wear mechanism of both HEAs was abrasive wear with a certain amount of delamination.