期刊
ACTA MATERIALIA
卷 166, 期 -, 页码 178-191出版社
PERGAMON-ELSEVIER SCIENCE LTD
DOI: 10.1016/j.actamat.2018.12.046
关键词
Austenite reversion; High-Mn steel; Atom probe tomography; Thermo-kinetic simulations; Curie temperature
资金
- FAPESP Sao Paulo Research Foundation (Brazil) [2017/04444-1]
- FAPESP [2015/26409-8, 2017/17170-7]
- CNPq (Brazilian National Research Council) [203077/2014-8]
- CNPq [302.136/2017-7, 303.826/2015-0]
- Fundacao de Amparo a Pesquisa do Estado de Sao Paulo (FAPESP) [15/26409-8] Funding Source: FAPESP
Austenite (gamma) reversion in a cold-rolled 17.6 wt.% Mn steel was tracked by means of dilatometry and in situ magnetic measurements during slow continuous annealing. A splitting of the gamma-reversion into two stages was observed to be a result of strong elemental partitioning between gamma and alpha'-martensite during the low temperature stage between 390 and 575 degrees C. Atom probe tomography (APT) results enable the characterization of the Mn-enriched reversed-gamma and the Mn-depleted remaining alpha'-martensite. Because of its lower Mn content, the reversion of the remaining alpha'-martensite into austenite takes place at a higher temperature range between 600 and 685 degrees C. APT results agree with partitioning predictions made by thermo-kinetic simulations of the continuous annealing process. The critical composition for gamma-nucleation was predicted by thermodynamic calculations (Thermo-Calc) and a good agreement was found with the APT data. Additional thermo-kinetic simulations were conducted to evaluate partitioning-governed gamma-growth during isothermal annealing at 500 degrees C and 600 degrees C. Si partitioning to gamma was predicted by DICTRA and confirmed by APT. Si accumulates near the moving interface during gamma-growth and homogenizes over time. We used the chemical composition of the remaining alpha'-martensite from APT data to calculate its Curie temperature (T-Curie) and found good agreement with magnetic measurements. These results indicate that elemental partitioning strongly influences not only gamma-reversion but also the T-Curie of this steel. The results are important to better understand the thermodynamics and kinetics of austenite reversion for a wide range of Mn containing steels and its effect on magnetic properties. (C) 2018 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.
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