Kinetics evaluation of nanostructured high-entropy material (AlNiCu)0.8(ZnSn)0.2, and its structural, thermal and magnetic properties

Abstract

A nanostructured high-entropy alloy based on brass and bronze compositions, (AlNiCu)₀.₈(ZnSn)₀.₂, was successfully synthesized via mechanical alloying. The synthesis kinetics were systematically investigated by correlating x-ray diffraction patterns, differential scanning calorimetry curves, and vibrating-sample magnetometry hysteresis profiles. Phase nucleation initiates within the first hour of milling, and thermal analysis indicates that the system stabilizes after four hours of milling. The alloy adopts a P6₃/mmc structure based on the AlCu intermetallic compound (ICSD-57667), with refinement density of 6.894 g/cm³. Nanocrystallites averaging 6.4 nm in size, constitute 55.3% of the microstructure, while the remaining 44.7% represent an interfacial component. Rietveld refinement confirms the structural model, revealing preferential vacancies at the Wyckoff 2d site (⅓, ⅔, ¾), which introduces occupation asymmetry to the structure. Thermally, the alloy exhibits a specific heat (C_p = 0.4398 J/gK) consistent with the rule of mixtures and a thermal diffusivity (α = 5.46 mm²/s). Notably, thermal diffusivity oscilates with milling stages reflecting competing mechanisms. The derived thermal conductivity (K = 16.94 W/mK) aligns with other high-entropy alloys. Magnetically, the material displays semihard behavior (H_c = 234.81 Oe), with low specific saturation magnetization (σ = 0.59 emu/g) and remanence (b = 0.13 emu/g).