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Stability of Retained Austenite in a Nb Microalloyed Mn-Si TRIP Steel
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1998
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Materials ScienceEngineeringSuperalloyMechanical EngineeringRetained AusteniteMn-si Trip SteelHigh Strength Low Alloy SteelVolume FractionThermomechanical ProcessingMechanics Of MaterialsMicrostructure
The effect of thermomechanical processing on the volume fraction and stability of retained austenite in a Nb microalloyed Mn-Si TRIP steel was investigated. In one set of tests, specimens were isothermally held at 400 °C for a series of different times, then air cooled to room temperature. In another set of tests, specimens were continuously cooled to room temperature at a cooling rate of 2 °C/s or 10 °C/s. The former generated a mixed microstructure of ferrite + bainite + retained austenite, while the latter produced a microstructure of bainite + martensite + retained austenite. It was found that the stability of retained austenite against a strain induced transformation to martensite increases with increasing carbon concentration, decreasing size and hard surrounding phase.