2 - Dynamic plasticity of metals

Abstract

The plastic deformation of metals is governed by the microstructure of the material and its response to external loading in the given conditions, including particularly the mode and rate of loading and the ambient temperature. At low and intermediate strain rates, the plastic deformation and strength of metals are controlled primarily by the thermally activated component of dislocation motion, while at higher strain rates the motion of dislocations becomes increasingly impeded by the so-called drag effects, leading to a faster increase in the flow stress of the material. At suitable strain rate-temperature combinations, the plasticity of metals can also be influenced by the diffusion of solute atoms to the (jerkily) moving dislocations, leading to an “anomalous” increase in the strength with increasing temperature, known as the dynamic strain aging effect. This Chapter describes all the main phenomena influencing the plasticity of metals at different strain rates and temperatures, how the microstructure of the metal influences the dynamic plasticity of modern metals, and how the strain rate and temperature affect the different deformation mechanisms, such as dislocation glide, mechanical twinning, and phase transformations, and the choice between them. The Chapter also describes selected approaches to the modeling of dynamic plasticity.