Recrystallization is to a large extent responsible for their final mechanical properties. This article commences with a discussion on static recrystallization (SRX) and dynamic recrystallization (DRX). The DRX includes continuous dynamic recrystallization (CDRX) and discontinuous dynamic recrystallization (DDRX). The article discusses the assumptions and simplifications for the Avrami analysis. It describes the effects of nucleation and growth rates on recrystallization kinetics and recrystallized grain size based on the Johnson-Mehl-Avrami-Kolmogorov model for static recrystallization. The article reviews the kinetics of DRX with the aid of the Avrami relations. It considers the basic framework of the mesoscale approach for DDRX, including the three basic equations for grain size changes, strain hardening and dynamic recovery, and nucleation. The article explains the mesoscale approach for CDRX to predict microstructural evolutions occurring during hot deformation, along with an illustration of the main features of the CDRX mesoscale model.

Thermomechanical processing (TMP) refers to various metal forming processes that involve careful control of thermal and deformation conditions to achieve products with required shape specifications and good properties. This article describes TMP methods in producing hot-rolled steel and reviews how improvements in the strength and toughness depend on the synergistic effect of microalloy additions and on carefully controlled thermomechanical conditions. It discusses TMP variables and the general distinctions between conventional hot rolling and common types of controlled-rolling schedules. The article describes the metallurgical processes in grain refinement of austenite steel by hot working, such as recovery and recrystallization and strain-induced transformation. The grain refinement in high strength low alloy steel by alloy addition is also discussed. The article provides an outline on the key stages of deformation, and the required metallurgical information at each of these stages.

The systematic study of microstructural evolution during deformation under hot working conditions is important in controlling processing variables to achieve dimensional accuracy. This article explains the microstructural features that need to be modeled and provides an outline of the principles and achievements of each of the various microstructural models, including black-box modeling, gray-box modeling, white-box modeling, and hybrid modeling.

Plastic deformation can occur in metals from various mechanisms, such as slip, twinning, diffusion creep, grain-boundary sliding, grain rotation, and deformation-induced phase transformations. This article emphasizes on the mechanism of slip and twinning under cold working conditions. It discusses the factors on which the structures developed during plastic deformation depend. These factors include crystal structure, amount of deformation, composition, deformation mode, and deformation temperature and rate. The article illustrates the microstructural features that appear after substantial deformation when revealed through metallographic investigation.