On the spherical nanoindentation creep of metallic glassy thin films at room temperature

Metallic glassy thin films with eight kind of compositions were successfully prepared on Si substrate by magnetron sputtering. The room-temperature creep tests were performed at plastic regions for each sample relying on spherical nanoindetation. The creep deformations were studied by recording the total creep displacement and strain after 2000 s holding. More pronounced creep deformation was observed in the sample with lower glass transition temperature (Tg). Strain rate sensitivity (SRS) was then calculated from the steady-state creep and exhibited a negative correlation with increasing Tg. It is suggested that creep mechanism of the nano-sized metallic glass was Tg-dependent, according to the demarcation of SRS values. Based on the obtained SRS, shear transformation zone (STZ) size in each sample could be estimated. The results indicated that an STZ involves about 25-60 atoms for the employed eight samples and is strongly tied to Tg. The characteristic of STZ size in metallic glassy thin films was discussed in terms of applied method and deformation modes.