A novel high-entropy alloy with exceptional strength and elongation via bimodal grains and lamellar nano-precipitates

This study presents a new effective approach for enhanced mechanical properties of the high-entropy alloy (HEA) Al7.3Co21.3Cr10.7Ti4.9Fe21.3Ni32.0Cu2.5 obtained by cold-rolling of columnar grains and subsequent annealing. This processing strategy aims to construct a microstructure of bimodal grains and coherent lamellar nano-precipitates. An ultrahigh strength of ∼1.68 GPa and a high elongation of ∼13.5% after annealing at 700 °C for 4 h were obtained, which are superior to those of previously reported similar HEAs. The ultrahigh strength originates mainly from the lamellar nano-precipitates strengthening and the bimodal grain size; however, the large elongation correlates to a progressive work-hardening mechanism regulated by the collaborative deformation of the ultrafine grains and the coarse grains and the unique nano-lamellar precipitates. This study provides a new strategy to utilize bimodal grains and coherent nano-precipitates in the development of HEAs or other similar alloys.