Hot Deformation Behavior of a High-Mn Austenitic Steel for Cryogenic Liquified Natural Gas Applications
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JMEPEG https://doi.org/10.1007/s11665-020-05011-5
Hot Deformation Behavior of a High-Mn Austenitic Steel for Cryogenic Liquified Natural Gas Applications Yong Chen, Xiao-Ming Zhang, Zhi-Hui Cai, Hua Ding, Ming-ming Pan, and Heng-Sen Li (Submitted November 15, 2018; in revised form October 31, 2019) Hot deformation behavior of a high-Mn austenitic steel was investigated employing hot compression tests at different temperatures and strain rates. The flow behavior related to deformation temperature and strain rate was analyzed. Microstructures and grain boundary characteristics of the deformed specimens quenched at selected conditions were examined using SEM-EBSD. It was observed that the flow stress and critical characteristic parameters were sensitive to deformation temperature and strain rate. Grain boundary bulging was the main nucleation mechanism which signified discontinuous dynamic recrystallization played a vital role in microstructure evolution. Strain rate had a complex influence on DRX kinetics and the formation of R3 boundaries. At high strain rates, the higher stored energy and adiabatic temperature rise induced the boundary to migrate at a higher velocity, thus accelerating the nucleation of DRX grains and increasing the frequency of twinning. At low strain rates, longer time was available for grain boundary migration which facilitated the growth of DRX grains and the nucleation of annealing twins. However, at intermediate strain rates, sluggish recrystallization kinetics and annealing twins evolution were observed as the stored energy was not sufficiently high and the time available for grain boundary migration was also fairly short. Keywords
dynamic recrystallization, high-Mn austenitic steel, hot deformation, R3 boundaries
1. Introduction As environmental problems are getting more serious, demands for the development of environmentally friendly energy sources have increased. Natural gas is a promising alternative energy source and may well take the place of coal as the worldÕs second-biggest energy source by the year of 2035 (Ref 1). With the rapid rise in consumption, the storage and transportation of natural gas, especially liquefied natural gas (LNG), has become increasingly important over the past few years. Recently, high manganese austenitic steels have been developed as substitutes for conventional cryogenic materials such as 9%Ni steels, austenitic stainless steels, aluminum alloys and Invar alloys due to the lower cost and comparable strength, ductility, and toughness (Ref 2-4). Like other metals and alloys, hot working is the primary processing method for the production of high-Mn austenitic steels and dynamic recrystallization occurring during hot deformation is an important mechanism for the control of microstructures and various properties (Ref 5-8). And it has been reported that flow behavior and microstructural evolution during thermo-mechanical processing are significantly influYong Chen, Xiao-Ming Zhang, Ming-ming Pan, and Heng-Sen Li, State Key Laboratory of Rolling and Automation, Northe
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