Wear behaviour of Zr-based in situ bulk metallic glass matrix composites

Zr-based bulk metallic glass (BMG) and its in situ BMG matrix composites with diameter of 3 mm were fabricated by conventional Cu-mould casting method and the dry sliding wear behaviour of the BMG and composites was investigated. Compared to the pure BMG, the composites exhibited a markedly improved wear resistance from 10 to 48% due to the existence of various volume fractions of the ductile β-Zr dendritic phase embedded in the glassy matrix. The composites showed lower friction coefficient and wear rate than the pure BMG. Meanwhile, the surface wearing of the composite with a proper amount of β-Zr dendrites was less severe compared to that of the pure BMG. The worn surface of the composite was covered with mild grooves and some fine wear debris, which exhibited the characteristic of a mild abrasive wear. The improvement of the wear resistance of the composite with the proper amount of β-Zr crystalline phase is attributed to the fact that the β-Zr crystalline phase distributed in the amorphous matrix has some effective load bearing, plastic deformation and work hardening ability to decrease strain accumulation and the release of strain energy in the glassy matrix, restrict the expanding of shear bands and cracks, and occur plastic deformation homogeneously.