Nanoscopic tribological characteristics of a cryogenically cycled Zr-based metallic glass

Optimized macroscopic tribological behavior can be anticipated in metallic glasses (MGs) by cryogenic cycling treatment (CCT), which is attributed to enhanced plasticity. However, the intrinsic friction mechanisms of MGs induced by cryogenic rejuvenation are still poorly understood. In the present study, nanoscopic wear tests were conducted on the Zr-based MGs surface with different CCT cycles using atomic force microscopy (AFM). After CCT treatment with 100 cycles, the MG displays the highest adhesion and ploughing frictions, but significantly improved anti-wear properties. Adhesion tests and molecular dynamics simulations disclose that the increased adhesion is attributed to the dominance of liquid-like regions in the CCT-treated MGs, and the impact of reduced hardness and weak elastic recovery results in the deteriorated ploughing friction. The enhanced plasticity effectively dissipates the strain from the AFM tip through multiple shear bands and weakens the adhesion during deformation, giving rise to excellent wear resistance. This study elucidates the promoting effect of CCT on the outstanding anti-wear performance of MGs, and is helpful for the development of novel alloys.