Dynamic recrystallization

About: Dynamic recrystallization is a research topic. Over the lifetime, 9818 publications have been published within this topic receiving 207083 citations.

Current issues in recrystallization: a review

Abstract: The current understanding of the fundamentals of recrystallization is summarized. This includes understanding the as-deformed state. Several aspects of recrystallization are described: nucleation and growth, the development of misorientation during deformation, continuous, dynamic, and geometric dynamic recrystallization, particle effects, and texture. This article is authored by the leading experts in these areas. The subjects are discussed individually and recommendations for further study are listed in the final section.

Dynamic and post-dynamic recrystallization under hot, cold and severe plastic deformation conditions

Abstract: The evolution of the new microstructures produced by two types of dynamic recrystallization is reviewed, including those brought about by severe plastic deformation (SPD). The microstructural changes taking place under these conditions and the associated mechanical behaviors are described. During the conventional discontinuous dynamic recrystallization (dDRX) that takes place at elevated temperatures, the new grains evolve by nucleation and growth in materials with low to medium stacking fault energies (SFE). On the other hand, new ultrafine grains can be produced in any material irrespective of the SFE by means of SPD at relatively low temperatures. These result from the gradual transformation of the dislocation sub-boundaries produced at low strains into ultrafine grains with high angle boundaries at large strains. This process, termed in situ or continuous dynamic recrystallization (cDRX), is still not perfectly understood. This is because many SPD methods provide data concerning the microstructural changes that take place but little information regarding the flow stress behavior. By contrast, multi-directional forging (MDF) provides both types of data concurrently. Recent studies of the deformation behavior of metals and alloys under SPD conditions, carried out using MDF as well as other SPD methods, are synthesized and the links between the microstructural and mechanical observations are examined carefully. Some models for grain formation under SPD conditions are discussed. Next, the post-dynamic recrystallization behavior, i.e. that of annealing after both dDRX and cDRX, is described. The differing annealing behaviors result from the differences in the natures of the deformed microstructures. Finally, an integrated recrystallization model for these phenomena, i.e. dynamic and static recrystallization of both the continuous and discontinuous types, is presented and discussed.

The eastern Tonale fault zone: a ‘natural laboratory’ for crystal plastic deformation of quartz over a temperature range from 250 to 700 °C

Abstract: Near the eastern end of the Tonale fault zone, a segment of the Periadriatic fault system in the Italian Alps, the Adamello intrusion produced a syn-kinematic contact aureole. A temperature gradient from ∼250 to ∼700 °C was determined across the Tonale fault zone using critical syn-kinematic mineral assemblages from the metasedimentary host rocks surrounding deformed quartz veins. Deformed quartz veins sampled along this temperature gradient display a transition from cataclasites to mylonites (frictional–viscous transition) at 280±30 °C. Within the mylonites, zones characterized by different dynamic recrystallization mechanisms were defined: Bulging recrystallization (BLG) was dominant between ∼280 and ∼400 °C, subgrain rotation recrystallization (SGR) in the ∼400–500 °C interval, and the transition to dominant grain boundary migration recrystallization (GBM) occurred at ∼500 °C. The microstructures associated with the three recrystallization mechanisms and the transitions between them can be correlated with experimentally derived dislocation creep regimes. Bulk texture X-ray goniometry and computer-automated analysis of preferred [c]-axis orientations of porphyroclasts and recrystallized grains are used to quantify textural differences that correspond to the observed microstructural changes. Within the BLG- and SGR zones, porphyroclasts show predominantly single [c]-axis maxima. At the transition from the SGR- to the GBM zone, the texture of recrystallized grains indicates a change from [c]-axis girdles, diagnostic of multiple slip systems, to a single maximum in Y. Within the GBM zone, above 630±30 °C, the textures also include submaxima, which are indicative of combined basal 〈a〉- and prism [c] slip.

A review of dynamic recrystallization phenomena in metallic materials

Abstract: The dynamic recrystallization (DRX) phenomena occurring in different thermo-mechanical processing (TMP) conditions for various metallic materials are reviewed. Several types of DRX are described: discontinuous dynamic recrystallization (DDRX), continuous dynamic recrystallization (CDRX) and geometric dynamic recrystallization (GDRX). The terminologies used in this field are summarized, together with the key factors influencing the DRX processes including stacking fault energy, initial grain size, TMP conditions and second-phase particles. Both standard and advanced experimental techniques used to characterize DRX processes are examined. The focus is placed on the mechanisms of these three types of DRX, and the related numerical models.

Dislocation creep regimes in quartz aggregates

Abstract: Using optical and TEM microscopy we have determined that three regimes of dislocation creep occur in experimentally deformed quartz aggregates, depending on the relative rates of grain boundary migration, dislocation climb and dislocation production. Within each regime a distinctive microstructure is produced due primarily to the operation of different mechanisms of dynamic recrystallization. At lower temperatures and faster strain rates the rate of dislocation production is too great for diffusion-controlled dislocation climb to be an effective recovery mechanism. In this regime recovery is accommodated by strain-induced grain boundary migration recrystallization. With an increase in temperature or decrease in strain rate, the rate of dislocation climb becomes sufficiently rapid to accommodate recovery. In this regime dynamic recrystallization occurs by progressive subgrain rotation. With a further increase in temperature or decrease in strain rate dislocation climb remains sufficiently rapid to accommodate recovery. However, in this regime grain boundary migration is rapid, thus recrystallization occurs by both grain boundary migration and progressive subgrain rotation. The identification of the three regimes of dislocation creep may have important implications for the determination of flow law parameters and the calibration of recrystallized grain size piezometers. In addition, the identification of a particular dislocation creep regime could be useful in helping to constrain the conditions at which a given natural deformation has occurred.