Inhibited dynamic recovery and screw dislocation annihilation in multiple slip of fcc single crystals

Abstract

In face-centred cubic (fcc) crystals, the stress–strain curves of 〈111〉 crystals are remarkably insensitive to dynamic recovery compared to other orientations. This effect is attested by several early experimental studies on copper, aluminium and silver crystals. The inhibition of dynamic recovery is attributed to a reduction in the rate of annihilation of screw dislocations. The underlying mechanisms are investigated in terms of the reversal of the direction of the resolved stress in the cross-slip plane, which occurs when going from 〈001〉 to 〈111〉 orientations. Two distinct processes governing dynamic recovery in 〈111〉 crystals, acute cross-slip and backward annihilation, are examined and discussed. The second process arises because screw dislocation annihilation occurs along the direction opposite to that of the resolved applied stress in the cross-slip plane. It is concluded that, except possibly in aluminium, backward annihilation is always responsible for the inhibition of dynamic recovery in 〈111〉 crystals.

Acknowledgements

The authors are indebted to Dr W. Pantleon for drawing their attention to the inhibition of cross-slip in 〈111〉 crystals. Helpful discussions with Professor J. Bonneville and Dr U. F. Kocks are gratefully acknowledged.