Improving the ductility of high-strength NiAl-based high-entropy alloys by introducing hierarchical nanoscale phases

Abstract

This work explored the possibility of using high-entropy alloys (HEAs) to balance the strength and ductility of NiAl-based alloys. A novel Ni₃₅Al₃₅Co₁₀Cr₁₀Fe₁₀ HEA and a Ni₃₅Al₃₅Co₁₀Cr₅Fe₁₅ HEA were designed, and their microstructures and mechanical properties were investigated. The microstructures of both systems are all columnar dendrites, while the secondary dendrite arm spacing changes from 26.8 μm to 55.61 μm. Many hierarchical nanoscale (Cr, Fe)-rich BCCs, Cr-rich precipitates and Fe-rich precipitates are also generated. Furthermore, transmission electron microscopy (TEM) revealed that the nanoscale precipitates maintained coherent interfaces, thus enhancing the strengthening effect on the NiAl-based HEAs, which exhibited exceptional mechanical properties, with an ultimate compressive strength of 1900.6 MPa and a reasonable strain of 26.5 %. The proposed as-cast alloy exhibited superior mechanical properties.