Deformation-induced microstructural evolution at grain scale

During plastic deformation metals develop microstructures which may be analysed on several scales,spanning from crystallographic textures averaged over the entire sample to the scale of individualgrains. Even within individual grains, intragranular phenomena in the form of orientation gradients aswell as dislocation patterning by formation of dislocation boundaries occur. Experimental data andassociated data analysis at the grain scale and below will be presented to illustrate our current level ofunderstanding. The basis for the analysis is the crystallographic orientation of the grain as well as theslip systems that are activated.More specifically the origin of both inter- and intragranular orientation spread is analysed for a specificexample from tensile deformed interstitial-free steel [Oddershede et al. 2015]. A universal frameworkfor the patterns consisting of dislocation boundaries is presented for both fcc and bcc materials inseveral deformation modes, demonstrating a clear grain orientation dependence [Huang & Winther,2007]. This dependence has its origin in a dependence on the slip systems [Winther & Huang, 2007].This further implies that the dislocations in the boundaries come from the active slip systems, which isconfirmed by experimental data [McCabe et al. 2004; Wei et al., 2011; Hong, Huang, & Winther,2013]. The elastic interactions between these dislocations are the driving force for the patterning[McCabe et al. 2004; Wei et al., 2011; Winther, Huang & Hong 2015]. The current state ofunderstanding as well as the major outstanding challenges are discussed.