Research Projects

This research proposal focuses on developing multi-phase refractory compositionally complex alloys (RCCAs) for high-temperature applications (850-1150°C). These alloys, based on Nb-Ni systems, aim to combine BCC and FCC phases to achieve superior yield strength and ductility, addressing the limitations of conventional Ni-based superalloys, which lose strength above 800°C due to the suppression of strengthening mechanisms like Kear-Wilsdorf (KW) locks. Unlike traditional high-entropy alloys (HEAs) that rely on high configurational entropy for single-phase stability, RCCAs incorporate non-equiatomic compositions and multi-phase microstructures, including BCC, B2, and FCC phases, to optimize properties. The alloy design employs empirical parameters (VEC: 5.7-7.5, ϕ: 3.5-20) and CALPHAD simulations to predict phase stability and tailor compositions. Two RCCA, Ni-Nb based, are proposed, with VEC values of 6.0 and 6.1, respectively, indicating BCC and FCC phase stability. Thermo-Calc simulations suggest these alloys form multi-phase structures suitable for heat treatment to optimize properties. The alloys will be cast using vacuum arc melting, followed by homogenization and aging heat treatments. Mechanical testing at 850-1150°C and advanced microstructural characterization (SEM, TEM, XRD, APT) will establish structure-property relationships to guide the development of next-generation high-temperature structural materials with enhanced strength-ductility synergy.