Microstructure evolution and mechanical response of Co-free Ni2CrFeAl0.3Tix high-entropy alloys

Abstract

In this study, microstructure and mechanical behavior of Co-free Ni2CrFeAl0.3Tix high-entropy alloys are investigated. X-ray diffraction analysis show that a simple face-centered cubic (FCC) solid-solution structure is present in Ni2CrFeAl0.3Ti0.1 and Ni2CrFeAl0.3Ti0.2 alloys, while B2-type precipitation appears in Ni2CrFeAl0.3Ti0.3 alloy in addition to the FCC matrix. Tensile results reveal that with an increase in Ti content, the yield and tensile strength of the alloys increases while the ductility decreases, and fortunately a good balance between strength and ductility is attained in Ni2CrFeAl0.3Ti0.3 that exhibits an ultimate tensile strength of 1240 MPa combined with over 10 % fracture strain. This feature can be ascribed to the visible strain-hardening response, reduced stacking-fault energy (ranging from 56.5 to 37.4 mJ∙m−2) and very fine B2 precipitates due to Ti addition. This work would provide an insight into the design of low-cost Ti-containing alloys in the future.