Dynamic Recrystallization of Austenite in Ni-30 Pct Fe Model Alloy: Microstructure and Texture Evolution
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THE restoration processes that occurred during hot working of steels, such as dynamic recovery and recrystallization, govern both the flow behavior and the resulting microstructure. Dynamic recrystallization (DRX) is of great importance because it has the potential to decrease hot working loads, but more importantly it can lead to significant refinement of the microstructure, which will improve the mechanical properties of final products. Dynamic recrystallization is defined as formation of new recrystallized grains during the hot deformation. At the early stages of deformation, new grains are initially formed on the pre-existing grain boundaries and the deformed microstructure becomes gradually consumed by DRX grains as the deformation proceeds. Several DRX formation mechanisms have been proposed, which vary depending upon the deformation conditions[1–3] and steel composition.[1–6] The microstructure control through the DRX process requires a detailed knowledge of the grain/subgrain boundary structure evolution and crystallographic texture characteristics during hot deformation. The character of the deformed structure within the original grains is critically important for the nucleation and growth of DRX grains. This is because there is inhomogenity in the deformation throughout the structure, which can lead to large strain gradients and a high local dislocation density, which favors DRX nucleation. The deformation inhomogenity arises from HOSSEIN BELADI and PAVEL CIZEK, Research Academic, and PETER D. HODGSON, Professor, ARC Federation Fellow, are with the Centre for Material and Fibre Innovation, Deakin University, Geelong, Vic 3217, Australia. Contact e-mail: [email protected] Manuscript submitted November 4, 2008. Article published online March 18, 2009 METALLURGICAL AND MATERIALS TRANSACTIONS A
the differences in grain orientation[7–13] and the highangle grain boundary characteristics.[1–6] The character of the recrystallization texture will affect the substructure nature and evolution within DRX grains as well as the resulting mechanical properties and their anisotropy. The evolution of DRX texture has, however, received much less attention compared with static recrystallization due to the complexity of the DRX process. Although there have been a few studies on DRX texture development,[1–3] they mainly focused on the DRX nucleation mechanisms and microtexture analysis of areas near grain boundaries. However, little attention was given to separating the evolution of texture and substructure formation in the DRX regions and the remaining work-hardened structure. In addition, most research to date employed materials with different stacking fault energy to lowcarbon steels (i.e., copper and stainless steel) and the experimental conditions were far from the industrial schedules used in the actual hot working of these steels. The aim of the current study was to investigate the microstructure and texture evolution throughout the DRX process during hot deformation of austenite under conditions similar to those u
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