This second edition updates and expands on the class-tested first edition text, augmenting discussion of dynamic strain aging and austenitic stainless steels and adding a section on analysis of nickel-base superalloys that shows how the mechanical threshold stress (MTS) model, an internal state variable constitutive formulation, can be used to de-convolute synergistic effects. The new edition retains a clear and rigorous presentation of the theory, mechanistic basis, and application of the MTS model. Students are introduced to critical competencies such as crystal structure, dislocations, thermodynamics of slip, dislocation–obstacle interactions, deformation kinetics, and hardening through dislocation accumulation. The model described in this volume facilitates readers’ understanding of integrated computational materials engineering (ICME), presenting context for the transition between length scales characterizing the mesoscale (mechanistic) and the macroscopic. Presenting readers a model buttressed by detailed examples and applications, the textbook is ideal for students, practitioners, and materials researchers.