Nanoindentation experiments were carried out at strain rates of 0.05, 0.10, 0.15 and 0.20/s at indentation depths of 1000, 1500 and 2000 nm to investigate the nanomechanical behaviour of Ti-6Al-4V alloy. The strain rate had little influence on nanohardness, however, nanohardness as well as Young's modulus gradually decreased with the increase of indentation depth indicating strong indentation size effects. The relation between H 2 and 1/h exhibited a good linear relationship, and it is observed that the effect of strain gradient on r/r 0 is significant at high strain rates according to Nix and Gao strain gradient model. The analysis of plastic behaviour revealed that, strain rates had no significant effect on strain hardening exponent, but had little influence on yield stress.

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