Cycle duration dependent hardness and β relaxation behavior of cryogenic-thermal-cycle treated metallic glasses

Whilst it is well documented that cryogenic-thermal-cycling (CTC) treatment could effectively alter the microstructural features and mechanical behavior of metallic glasses (MGs), the underlying mechanism is still controversial. In the present study, the effects of CTC treatment frequency, which had not been reported in previous research, on the microstructure, hardness, volume of shear transformation zone (STZ) and β relaxation behavior of LaNiAl MG were characterized by altering the time duration of a single cycle. Experimental results demonstrated that the CTC-frequency/single-cycling-duration indeed plays crucial roles in determining the microstructure evolution and mechanical/relaxation behavior of the MG. It was proposed that the distinct rejuvenation degrees derived in the MGs with various CTC frequencies are determined by the size of shear transformation zones (STZs) and the energy input upon single cycling duration. Whether the input energy can activate the STZs entirely/partially/barely affects the microstructural evolution of the MGs and eventually alters their rejuvenated state and hardness. Therefore, the experimental results presented herein may demonstrate the potential application areas in structural materials where enhanced plasticity or controlled rejuvenation is beneficial.