Hardening and Failure Under Repeated Plastic Deformation. Communication 2. Multipass Deformation Under Thermomechanical Treatment Conditions.

High-temperature rotation forging of molybdenum is analyzed using an equation for flow stress under high strains. The level of the flow stress under high-temperature multipass deformation is determined by two independent processes: a continuous (from pass to pass) decrease in the grain size and deformation hardening whose contribution changes intricately as a result of an active recovery process, which is confirmed by electron-microscopic study of the structure at the process stage. It is shown that the process of high temperature deformation, including the multipass one, can be characterized by two strain values determined by the residual variation of the shape and by the dislocation density. Consequently, the development of technological conditions should be reduced to a search for an optimal combination of these two values by varying the temperature and the degree of deformation in the course of a pass.