Temperature and strain-rate dependence of flow stress of nanocrystalline nickel fabricated by electrolytic deposition

Nanocrystalline nickel, having a grain size of about 40 nm, was fabricated by electrolytic deposition and strain-rate jump tests were performed at temperaures between 77 and 473 K to obtain the strain-rate sensitivitym and the activation volume V∗. The values of m changed from about 0.05 to about 0.005 with increasing stress, indicating that the deformation is governed by the motion of glide dislocations. V∗ increased as the temperature increased from 77 to 200 K, but decreased with further increase in temperature. It is concluded that the rate-controlling deformation mechanism in nanocrystalline nickel is temperature sensitive and changes from forest dislocation cutting to dislocation bowing-out and depinning from grain boundaries as the temperature increases.