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This article is an attempt at highlighting recent advances made for understanding and modeling the phenomenon of dynamic recrystallization (DRX) prevalent in titanium alloys. Research work in recent years has focused on providing a rigorous description of key factors that influence the DRX process such as the effect of grain size, stacking fault energy, and other microstructural descriptors, thermomechanical processing, etc. The key addition of this work to existing literature is a critical commentary of important experimental as well as modeling efforts in recent years related to observing DRX in hexagonal close-packed (hcp) metals. We have attempted to directly compare, with reference to experiments, the effects of process variables such as strain rate, temperature, and composition on the occurrence of DRX in titanium alloys. A comprehensive review has been made of the experiments that have been carried out specifically to observe DRX in titanium alloys. This can aid modeling and validation efforts to accurately capture different facets of DRX for titanium alloys and other hcp metals. A similar comparison of the drawbacks and insights obtained from applying various modeling strategies, viz., FEM-based, phenomenological, or grid-based numerical methods for various alloys can provide valuable insights to choose appropriate modeling schemes or develop novel techniques to predict aspects of DRX such as preferred nucleation sites and evolution of microstructure, including grain boundaries and primary and secondary phases.

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The present study is an attempt to model dynamic recrystallization (DRX) in a single phase metal using a mean field crystal plasticity (MFCP) based approach. A new empirical equation is proposed to model nucleation, in which the nucleation rate is a function of
microstructure and plasticity descriptors that are known to affect DRX behavior, such as the temperature, strain rate, grain fineness and stored energy. Grains undergo nucleation when their dislocation density exceeds a threshold value. Subsequently, new grains grow based on the difference in stored deformation energy with respect to the average value over all grains. The MFCP-DRX model is able to correctly predict trends for the flow stress, dislocation density evolution, grain size evolution and kinetics across a range of temperatures and strain
rates for uniaxial compression. Transition of the flow stress from single to multiple peaks is observed with increasing temperature and decreasing strain rate, thus comparing well against known DRX trends. The evolutions of crystallographic texture during DRX in unaxial
compression and plane strain compression are compared against experimental observations. A sensitivity analysis is conducted to understand the effect of variables on nucleation and growth. The competition between nucleation and growth dominated deformation in different strain regimes is analyzed in detail across various temperatures and strain rates.