Study of phase evolution and phase stability in a novel FCC based Al30Ti35Mg5V10Fe8Cr12 lightweight high-entropy alloy processed by mechanical alloying

Abstract

High-entropy alloys (HEAs) have gained significant attention from researchers due to their exceptional mechanical properties. While most the reported lightweight high-entropy alloys have Body Centered Cubic (BCC), Hexagonal Close Packed (HCP), and complex intermetallic phases, there is growing interest in development of Face Centered Cubic (FCC) based Lightweight High-Entropy Alloys (LWHEA) for applications prioritizing energy efficiency. In this study, a design strategy for synthesizing a stable FCC-based LWHEA through multivariate optimization of elements and thermodynamic parameters was presented. A novel Al₃₀Ti₃₅Mg₅V₁₀Fe₈Cr₁₂ LWHEA was designed and processed through a mechanical alloying route with a theoretical density of 4.5 g/cc. The compaction of the alloy was performed by spark plasma sintering (SPS) at 890 ℃ and 60 MPa for 15 minutes. The hardness of sintered sample was found to be 550 ± 18 HV (5.3 GPa). Microstructural evolution of the alloy was studied using X-ray diffraction (XRD) and Scanning electron microscopy (SEM). The microstructural analysis of alloy revealed that a combination of FCC and BCC phases are present in milled sample as well as sintered sample. The phase stability was explained through Gibbs free energy calculations of competing phases.