A Comprehensive Study on Texture Development and Twin-Related Domain Evolution Following Hot Compression in a Super Aust
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SUPER austenitic stainless steels are widely used in various power plant and chemical industries due to its good combination of strength and corrosion resistance.[1–3] Hot deformation is employed to manufacture complex shapes and parts of the alloy which are extensively used in boilers and chemical pipelines.[4,5] Dynamic recrystallization (DRX) and dynamic recovery (DRV) are the two softening mechanisms that predominantly occur during hot deformation.[6–8] The occurrence of DRX during hot deformation has attracted attention as it plays a crucial role in microstructural evolution and grain refinement which eventually helps to reduce the forming load and optimize the mechanical K. ARUN BABU, YAHYA H. MOZUMDER, and SUMANTRA MANDAL are with the Department of Metallurgical and Materials Engineering, Indian Institute of Technology Kharagpur 721302, India. Contact e-mail: [email protected], [email protected] C.N. ATHREYA and V. SUBRAMANYA SARMA are with the Department of Metallurgical and Materials Engineering, Indian Institute of Technology Madras, Chennai 600036, India. Manuscript submitted December 10, 2019.
METALLURGICAL AND MATERIALS TRANSACTIONS A
properties.[9–11] Nevertheless, the DRX kinetics is often complex as it is influenced greatly by processing parameters such as temperature, strain rate,[12,13] strain[14] in addition to state of stress,[15] initial microstructure,[16] and precipitation,[17] etc. Thus, a better understanding of the influence of processing parameters on the DRX behavior of super austenitic stainless steels is necessary to control microstructure during hot working.[18,19] In addition to the evolution of strain-free grains, the grain boundary character distribution (GBCD) also changes during DRX.[6,20] Coincidence lattice boundariesP (CSL) P are a subset of high-angle boundaries and low ( £ 29) CSL boundaries are believed to have unique properties.[21,22] In view of this, these boundaries are often separately analyzed to understand the GBCD evolution during thermomechanical processing.[21] P Among CSL boundaries, the 3 annealing twin boundaries have gained great attention as these are found to play a key role in modifying GBCD[20,21] and controlling the kinetics of DRX.[20,23] It is well established that these P 3 boundaries are generated during nucleation and growth of DRX grains,[20,23,24] though the exact mechanisms and their dependence on processing parameters
are P not clear. Several researchers have pointed out that 3 twin boundary is generated due to growth accidents during strain-induced boundary migration (SIBM), and the twin density is dependent on the temperature and strain rates of deformation.[25–27] However, Pande’s growth accident model has considered the variation of twin density as a function of grain size alone and not on temperature and P strain rates.[28] Besides, it has been reported that P the 3 twin boundaries could also form through 3 regeneration mechanism in addition to P [20,21,29] During 3 regengrowth accident P phenomenon. P eration, the 3 boundaries e
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