Nanocrystalline AlCoFeNiTiZn high entropy Alloy: Microstructural, Magnetic, and thermodynamic properties

AlCoFeNiTiZn high entropy alloy was successfully produced in powder form by the mechanical alloying process. The ball-milled alloyed product was characterized by X-ray diffractometry, scanning electron microscopy, energy dispersive spectroscopy, and transmission electron microscopy techniques, which indicated that after 120 h of milling, the solid solution was formed as predicted by thermodynamic calculations. Mechanical alloying began to form the BCC phase almost at 30 h and the FCC phase after about 30 h. Nucleation and growth were the processes involved in the formation of these phases, as shown by the Johnson-Mehl-Avrami kinetic model. Sintering was then used to fabricate the alloy in bulk metallic form. The powders were cold pressed and sintered after 120 h of mechanical alloying using a tube furnace with a controlled atmosphere at 500 °C. A similar FCC + BCC phase mixture was present after sintering. The sintered sample also contained minor amounts of Gahnite (ZnAl2O4) spinel material. DSC analysis revealed that recrystallization occurred at 280 °C. The as-milled and as-sintered alloys exhibit semi-hard magnetic properties measured by vibrating sample magnetometer (VSM), with saturation magnetization values of 39.14 and 65.78 emu/g, respectively.