Indentation creep of an Fe-based bulk metallic glass

In this study, the room temperature creep behavior of Fe41Co7Cr15Mo14C15B6Y2 bulk metallic glass was investigated using nanoindentation technique with the maximum applied load ranging from 1 mN to 100 mN under different loading rates (0.01–2.5 mN s−1). The creep stress exponent was derived from the recorded displacement–holding time curve. It was found that the stress exponent increases rapidly from 2.87 to 6.37 with increasing indentation size, i.e. exhibiting a positive indentation size dependence. Furthermore, as the indentation loading rate increases from 0.01 mN s−1 to 2.5 mN s−1, the stress exponent decreases gradually from 4.93 to 0.94. The deformation mechanism causing the nanoindentation creep is discussed in the light of the “shear transformation zone” (STZ) which provides qualitative explanation for the observed plasticity in amorphous alloy.