Deformation Anisotropy of Annealed Zircaloy-2 as a Function of Fast Neutron Fluence

For unirradiated Zircaloys, plastic deformation occurs mostly by ?a?-type dislocation glide on prismatic planes. The critical resolved shear stress of the prismatic slip system is lower than that of the other deformation systems (?a? slip on basal planes, and ?a? or ?c+a? slip on pyramidal planes, and twinning). This means that the yield strength (and ultimate tensile strength) for directions with a strong basal pole texture is higher than directions with a strong prism pole texture. Irradiation increases the yield stress on all slip planes due to the formation of dislocation loops that act as barriers to slip. Experimental evidence from Zircaloy-2 samples irradiated at 70°C suggests that the increase in critical resolved yield stress due to irradiation is lower for basal compared with prism planes.