Mechanical and structure studies of Zr50Cu50 glass matrix composites during nano-indentation-a molecular dynamics study

In this paper we report molecular dynamics simulations of nano-indentation on Zr50Cu50 metallic glass matrix composite (14% crystalline volume fraction) at various strain rates. The objective of this paper is to investigate the effect of strain rate on the deformation behaviour and understand the deformation mechanism during deformation. Structural analysis during deformation is done by centro-symmetry parameter (CSP) studies. The load-displacement plots are drawn for the loading portion of indentation to analyze the deformation behaviour. It is found that strain rate has significant effect on the nature of the load-displacement plot. With increasing strain rate serrations decreased and flat load-displacement regime is observed with progress of indentation (similar to 10 angstrom) at strain rate of 1 x 10(11) s(-1). This could be due to atoms getting less time to get rearranged themselves so as to bear further load. Also, the structure studies by CSP indicated that, at low strain rates (2 x 10(10) s(-1) and 5 x 10(10) s(-1)) there is significant plastic deformation of the crystallite as compared to that at higher strain rate value of 1 x 10(11) s(-1) at a particular indentation depth. This indicates that there is load transfer from the glassy matrix to the crystallite much earlier at low strain rates. However, at indentation depths of 20 angstrom at all the strain rates amorphization of the crystallite is observed.