The plastic deformation of polycrystalline metals is primarily carried by the crystallographic glide of dislocations and growth of deformation twins. According to the thermodynamic theory of slip, dislocation motion is thermally activated, while deformation twinning is an athermal process. Dislocations must overcome barriers in order to move, while twins must relax the stored energy while growing. These concepts define the critical activation stresses on a slip or twin crystallographic system and how they evolve with plastic strain. This article reviews recent advances in the development of a model for the critical activation stresses for thermally activated glide and the expansion of deformation twins, its implementation into polycrystal plasticity models, and several applications for predicting the constitutive response of polycrystalline metals. Calculations are performed for a range of polycrystalline metals differing in microstructural complexity and crystal structure. These examples include face‐centered cubic AA6022‐T4, IN718, Haynes 25, and pure Cu, body‐centered cubic Nb, Ta, Ta‐10W, and steel DP590, hexagonal close‐packed pure Be, pure Zr, pure Ti, AZ31, Mg4Li, and orthorhombic U. Excellent agreement with experimental measurement are demonstrated in terms of texture, stress–strain response, and geometrical changes in the samples during deformation for all these metals.
