Influence of microstructural heterogeneity and plastic strain on geometrically necessary dislocation structure evolution in single-phase and two-phase alloys

Deformation of single phase and two phase materials can be heterogeneous depending on the grain size distribution, orientation of the grains, amount and arrangement of the second phase and phase transformation during plastic deformation and twins. The deformation heterogeneity requires generation of geometrically necessary dislocations (GND) to maintain contact of the deforming grains and phases. Depending on the amount and character of deformation at the microscopic length scale, the evolution of the GND density changes. The present paper discusses the buildup of the GND density in different microstructural configurations using, single phase ferritic interstitial free (IF) steel, dual phase (DP) steel containing ferrite and martensite and austenitic stainless steel prone to deformation induced martensitic transformation and twining and whether GND density can be used as a descriptor of the deformation characteristics of the materials. The estimation of GND content using electron backscatter diffraction (EBSD) is recognized. The application potential of the present study is in understanding the in-grain deformation behavior of single phase IF steel, two phase DP steel, transformation induced plasticity assisted austenitic stainless steel to assess the forming of the steels for automobile applications. It should also facilitate the validation of strain gradient plasticity dependent damage model.