Design and characterization of novel multi-phase AlMgZnCuSi light-weight high-entropy alloy with high potential as PCM for energy storage applications

Abstract

This paper presents the design, synthesis, and characterization of a lightweight and cost-effective multi-phase eutectic high-entropy alloy, ${\mathrm{Al}}_{35}{\mathrm{Mg}}_{30}{\mathrm{Zn}}_{15}{\mathrm{Cu}}_{10}{\mathrm{Si}}_{10}$(at.%) with a density of 3.30 g/cm³. The chemical composition of the alloy was meticulously selected to have a mixture of eutectic and intermetallic phases. The alloy is produced by melting followed by a semisolid forging process conducted at 510 °C, employing various holding times to investigate the behavior and phase transformations associated with this alloy. The alloy showed four major phases: FCC ($\alpha$-Al) solid solution, Al₂Cu, Mg₂Si intermetallic, and FCC Mg-Al-Zn compounds. The semisolid forging process demonstrated remarkable plasticity through reducing the sample thickness by 35% and 70%. The alloy exhibited a high latent heat capacity of phase change, reaching up to 168.9 kJ/kg at around 450$°C$, where partial melting of the eutectic phase occurs. This value ranks this alloy among the highest values reported for high-temperature metallic phase change materials. The novel alloy by its nature also boasts partial melting at high temperatures, eliminating the need for costly heat transfer enhancement techniques required by other PCMs. The oxidation kinetics showed an increasing pattern of weight change, adhering to a parabolic rate law. The semisolid forged sample, which was 70% oxidized, displayed the lowest parabolic rate constant of 0.233 × 10⁻² g/cm² after 500 min indicating a low oxidation rate, thus having good oxidation resistance.