Effect of size, temperature and strain rate on dislocation density and deformation mechanisms in Cu nanowires

Abstract: In the present study, molecular dynamics (MD) simulations have been performed to understand the effect of nanowire size, temperature and strain rate on the variations in dislocation density and deformation mechanisms in $<$100$>$ Cu nanowires. The nanowire size has been varied in the range 1.446-43.38 nm with a constant length of 21.69 nm. Different temperatures varying from 10 K to 700 K and strain rates in the range of $5 \times 10^7$ - $1 \times 10^9$ s$^{-1}$ have been considered. For all the conditions, the variations in dislocation density $(\rho)$ has been calculated as a function of strain. The results indicate that the variations in dislocation density exhibits two stages irrespective of the conditions: (i) dislocation exhaustion at small strains followed by (ii) dislocation starvation at high strains. However, with decreasing size and increasing temperature, the rate of dislocation exhaustion increases, which results in early transition from dislocation exhaustion stage to dislocation starvation stage. Similarly, with increasing strain rate, the rate of dislocation exhaustion and also the transition strain increases.