Contribution of primary and “forest” dislocations to deforming stress in zinc crystals under basal slip

Abstract

The effect of “forest” dislocations from the [11 2 2] 〈11 2 3〉 slip system on strain-hardening parameters is studied under basal slipping through the (0001)〈11 2 0〉 slip system in Zn crystals. By means of the stress relaxation method, the flow stress is divided into short- and long-range components at different stages of the hardening curve and the effect of “forest” dislocation density on them is studied. The contribution of “forest” dislocations and primary basal dislocations to a long-range component, τ G, is defined. For equal densities of primary ( ϱ b) and “forest” dislocations ( ϱ f) (∼5 × 10 5 cm −2) the contribution of “forest” dislocations to the τ G-component at stage A is shown to exceed that of primary dislocations, and for ϱ f ⪢ 5 × 10 5 cm −2 the flow stress is mainly determined by “forest” dislocations. It is noted that Seeger's theory takes into incomplete account the role of “forest” dislocations in the strain hardening of h.c.p. metals.