Optimizing dry-wear performance of a Ti-based high entropy bulk metallic glass via isothermal annealing

The evolution of microstructure, thermal stability, mechanical response behavior and tribological properties of the Ti₂₀Zr₂₀Cu₂₀Hf₂₀Be₂₀ high entropy bulk metallic glass (HE-BMG) before and after isothermal annealing were systematically studied. The results demonstrate that isothermal annealing affects the mechanical and tribological properties by modifying the microstructure and the consumption of free volume in the structure. Although the strength/hardness of HE-BMG can be improved after the isothermal annealing before crystallization, the deterioration of shear plastic deformation leads to serious brittle fracture, thus cancelling out the contribution of strength to wear resistance and resulting in negligible variation of wear rates. When the crystallization isothermal annealing is performed, the wear resistance can be dramatically enhanced and the wear mechanism changes to slight abrasive and oxidation wear, which can be mainly attributed to the good co-deformation between the amorphous matrix and precipitated crystalline phases.