Effect of Strain Rate on Evolution of the Deformation Microstructure and Texture in Polycrystalline Copper and Nickel

Abstract

The evolution of crystallographic texture in polycrystalline copper and nickel has been studied. The deformation texture evolution in these two materials over seven orders of magnitude of strain rate from 3 × 10⁻⁴ to ~2.0 × 10⁺³ s⁻¹ show little dependence on the stacking fault energy (SFE) and the amount of deformation. Higher strain rate deformation in nickel leads to weaker $\left\langle {101} \right\rangle$ texture because of extensive microband formation and grain fragmentation. This behavior, in turn, causes less plastic spin and hence retards texture evolution. Copper maintains the stable end $\left\langle {101} \right\rangle$ component over large strain rates (from 3 × 10⁻⁴ to 10⁺² s⁻¹) because of its higher strain-hardening rate that resists formation of deformation heterogeneities. At higher strain rates of the order of 2 × 10⁺³ s⁻¹, the adiabatic temperature rise assists in continuous dynamic recrystallization that leads to an increase in the volume fraction of the $\left\langle {101} \right\rangle$ component. Thus, strain-hardening behavior plays a significant role in the texture evolution of face-centered cubic materials. In addition, factors governing the onset of restoration mechanisms like purity and melting point govern texture evolution at high strain rates. SFE may play a secondary role by governing the propensity of cross slip that in turn helps in the activation of restoration processes.