Comparative Surface Hardening Effects of Edge and Screw Dislocations in Aluminum Single Crystals

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Abstract
The present experiment was conducted to investigate whether edge and screw dislocations play different roles in the surface work-hardening of metals deformed in tension. The sides of the crystals were so oriented that one pair of sides was parallel to the Burgers vector of the dislocations of the primary slip system. The crystals were deformed in tension to 0.5% and then unloaded. Subsequently, some crystals were masked on one pair of sides, and others were masked on the other pair of sides. They were then electropolished to remove the surface layers from the unmasked faces. This operation was repeated at several strains. At small strains, edge and screw dislocations play different roles in the surface work-hardening mechanism. However, at larger strains, both edge and screw dislocations harden the surface equally, and preferential surface work-hardening increases as the stress level increases.