Dynamic recrystallization mechanisms operating in a Ni–20%Cr alloy under hot-to-warm working

Dudova, Nadezhda; Belyakov, Andrey; Sakai, Taku; Kaibyshev, Rustam

doi:10.1016/j.actamat.2010.02.032

Cited by 173 publications

(92 citation statements)

References 23 publications

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“…One of the most promising methods for obtaining ultrafine-grained steels and alloys is large strain plastic working [17][18][19][20]. Ultrafine-grained structures can be achieved in various metals and alloys through continuous dynamic recrystallization under warm-working conditions which results in the progressive development of ultrafine grains rather than deformation subgrains [21][22][23][24][25]. In austenitic stainless steels, the continuously recrystallized microstructures are characterized by a very low fraction of Σ3 CSL boundaries because the boundaries in ultrafine-grained microstructures develop without any long-range boundary migration [26,27].…”

Section: Introductionmentioning

confidence: 99%

Σ3 CSL boundary distributions in an austenitic stainless steel subjected to multidirectional forging followed by annealing

Tikhonova

Kuzminova

Fang

et al. 2014

Philosophical Magazine

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The effect of processing and annealing temperatures on the grain boundary characters in the ultrafine-grained structure of a 304-type austenitic stainless steel was studied. An S304H steel was subjected to multidirectional forging (MDF) at 500-800°C to total strains of~4, followed by annealing at 800-1,000°C for 30 min. The MDF resulted in the formation of ultrafine-grained microstructures with mean grain sizes of 0.28-0.85 μm depending on the processing temperature. The annealing behaviour of the ultrafine-grained steel was characterized by the development of continuous post-dynamic recrystallization including a rapid recovery followed by a gradual grain growth. The post-dynamically recrystallized grain size depended on both the deformation temperature and the annealing temperature. The recrystallization kinetics was reduced with an increase in the temperature of the preceding deformation. The grain growth during post-dynamic recrystallization was accompanied by an increase in the fraction of Σ3 n CSL boundaries, which was defined by a relative change in the grain size, i.e. a ratio of the annealed grain size to that evolved by preceding warm working (D/D 0 ). The fraction of Σ3 n CSL boundaries sharply rose to approximately 0.5 in the range of D/D 0 from 1 to 5, which can be considered as early stage of continuous post-dynamic recrystallization. Then, the rate of increase in the fraction of Σ3 n CSL boundaries slowed down significantly in the range of D/D 0 > 5. A fivefold increase in the grain size by annealing is a necessary condition to obtain approximately 50% Σ3 n CSL boundaries in the recrystallized microstructure.

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Section: Introductionmentioning

confidence: 99%

Σ3 CSL boundary distributions in an austenitic stainless steel subjected to multidirectional forging followed by annealing

Tikhonova

Kuzminova

Fang

et al. 2014

Philosophical Magazine

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“…However, bulging HAGBs were not necessary in the nucleation of DRX in this study ( Figure 9). Here, the nucleation mechanism of DRX was similar to that under low deformation temperature conditions [23]. In this study, a very low strain rate, high deformation temperature, and large grain size promoted the formation of LAGBs and subgrains.…”

Section: Drx Mechanism Under Very Low Strain-ratementioning

confidence: 55%

“…e nucleation mechanisms of DRX are complex and depend on many factors, such as the deformation temperature [23], strain rate [14,16], grain size [24], precipitation [25], and stacking fault energy [16,26]. Further studies are required to clarify the effects of these factors.…”

Section: Drx Mechanism Under Very Low Strain-ratementioning

confidence: 99%

Microstructure Evolution and Surface Cracking Behavior of Superheavy Forgings during Hot Forging

Wang

Xue

Zhao

2018

Advances in Materials Science and Engineering

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In recent years, superheavy forgings that are manufactured from 600 t grade ingots have been applied in the latest generation of nuclear power plants to provide good safety. However, component production is pushing the limits of the current free-forging industry. Large initial grain sizes and a low strain rate are the main factors that contribute to the deformation of superheavy forgings during forging. In this study, 18Mn18Cr0.6N steel with a coarse grain structure was selected as a model material. Hot compression and hot tension tests were conducted at a strain rate of 10 −4 ·s −1. e essential nucleation mechanism of the dynamic recrystallization involved low-angle grain boundary formation and subgrain rotation, which was independent of the original highangle grain boundary bulging and the presence of twins. Twins were formed during the growth of dynamic recrystallization grains. e grain refinement was not obvious at 1150°C. A lowering of the deformation temperature to 1050°C resulted in a fine grain structure; however, the stress increased significantly. Crack-propagation paths included high-angle grain boundaries, twin boundaries, and the insides of grains, in that order. For superheavy forging, the ingot should have a larger height and a smaller diameter.

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“…The coarse remnants of the original grains are surrounded by numerous DRX grains in the sample compressed at 1173 K ( Figure 2). The development of DRX grains readily takes place along the original grain boundaries [1,3,10]. Therefore, so-called necklace microstructures are evolved in the partially-recrystallized samples in Figure 2.…”

Section: Deformation Microstructuresmentioning

confidence: 99%

“…The flow stress during hot deformation of various metals and alloys also depends on the deformation conditions and can be expressed by a power law function of Z. Therefore, a power law generally holds between the flow stress and the DRX grain size with a grain size exponent of about −0.7 for hot working conditions [10][11][12].…”

Section: Introductionmentioning

confidence: 99%

Grain Boundary Assemblies in Dynamically-Recrystallized Austenitic Stainless Steel

Tikhonova

Dolzhenko

Kaibyshev

et al. 2016

Metals

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Abstract:The grain boundary misorientation distributions associated with the development of dynamic recrystallization were studied in a high-nitrogen austenitic stainless steel subjected to hot working. Under conditions of discontinuous dynamic recrystallization, the relationships between the grain or subgrain sizes and flow stresses can be expressed by power law functions with different grain/subgrain size exponents of about −0.76 (for grain size) or −1.0 (for subgrain size). Therefore, the mean grain size being much larger than the subgrain size under conditions of low flow stress gradually approaches the size of the subgrains with an increase in the flow stress. These dependencies lead to the fraction of high-angle boundaries being a function of the flow stress. Namely, the fraction of ordinary high-angle boundaries in dynamically-recrystallized structures decreases with a decrease in the flow stress. On the other hand, the fraction of special boundaries, which are associated with annealing twins, progressively increases with a decrease of the flow stress.

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Dynamic recrystallization mechanisms operating in a Ni–20%Cr alloy under hot-to-warm working

Cited by 173 publications

References 23 publications

Σ3 CSL boundary distributions in an austenitic stainless steel subjected to multidirectional forging followed by annealing

Σ3 CSL boundary distributions in an austenitic stainless steel subjected to multidirectional forging followed by annealing

Microstructure Evolution and Surface Cracking Behavior of Superheavy Forgings during Hot Forging

Grain Boundary Assemblies in Dynamically-Recrystallized Austenitic Stainless Steel

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