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Shahab Kazemi

Academic rank: Assistant Professor
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Education: PhD.
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Faculty: Faculty of Engineering
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Research

Title
Dynamic recrystallization and precipitation in high manganese austenitic stainless steel during hot compression
Type
JournalPaper
Keywords
austenitic stainless steel; hot deformation; dynamic recrystallization; precipitation; activation energy
Year
2014
Journal International Journal of Minerals Metallurgy and Materials
DOI
Researchers ّamir momeni ، Shahab Kazemi ، gholam ebrahimi ، alireza maldar

Abstract

Dynamic recrystallization and precipitation in a high manganese austenitic stainless steel were investigated by hot compression tests over temperatures of 950-1150°C at strain rates of 0.001 s−1-1 s−1. All the flow curves within the studied deformation regimes were typical of dynamic recrystallization. A window was constructed to determine the value of apparent activation energy as a function of strain rate and deformation temperature. The kinetics of dynamic recrystallization was analyzed using the Avrami kinetics equation. A range of apparent activation energy for hot deformation from 303 kJ/mol to 477 kJ/mol is obtained at different deformation regimes. Microscopic characterization confirms that under a certain deformation condition (medium Zener-Hollomon parameter (Z) values), dynamic recrystallization appears at first, but large particles can not inhibit the recrystallization. At low or high Z values, dynamic recrystallization may occur before dynamic precipitation and proceeds faster. In both cases, secondary phase precipitation is observed along prior austenite grain boundaries. Stress relaxation tests at the same deformation temperatures also confirm the possibility of dynamic precipitation. Unexpectedly, the Avrami's exponent value increases with the increase of Z value. It is associated with the priority of dynamic recrystallization to dynamic precipitation at higher Z values.