Influence of Intercritical Annealing Temperature on Microstructure and Mechanical Properties of a Cold-Rolled Medium-Mn Steel

Abstract

Medium-Mn steels are characterized by ultrafine-grained (UFG) duplex microstructure consisting of ferrite and a large amount of retained austenite. Intercritical annealing is of great importance to achieving the UFG duplex microstructure and adjusting amount as well as stability of retained austenite. In the present work, the influence of intercritical annealing temperature on the microstructure and mechanical properties was investigated in a cold-rolled medium-Mn steel Fe-12Mn-3Al-0.05C. Particularly, the dependence of microstructural morphology on intercritical annealing temperature was emphasized to reveal the genesis of the microstructural morphology in medium-Mn steels. The ferrite-austenite duplex microstructure manifested an elongated morphology in the specimen annealed at 555 • C, which inherited the lath structure of the cold-rolled state. The medium-Mn steel exhibited a continuous yielding behavior and a relatively low strain-hardening rate. With an increase in intercritical annealing temperature up to 650 • C, the amount of retained austenite increased and microstructure was partially recrystallized, showing a mixture of elongated and equiaxed grain morphologies. When the intercritical annealing was applied at 700 • C, the medium-Mn steel mainly exhibited recrystallized microstructure with equiaxed morphology. The optimal balance between the amount and the stability of retained austenite led to an enhancement of strain hardening and ductility. With a further increase in the intercritical annealing temperature to 750 • C, the medium-Mn steel possessed pronounced strain-hardening behavior at the beginning of the tensile deformation with deteriorated ductility.

Influence of Microstructural Morphology on Hydrogen Embrittlement in a Medium-Mn Steel Fe-12Mn-3Al-0.05C

“…More recently, deformation-induced twinning was found in MMnS with a manganese content of 6 to 12 wt% after the α'-martensite formation, which was referred to as a medium-Mn twinning-induced-plasticity (TWIP) + TRIP steel [3,4]. Tailoring the mechanical properties by modifying the microstructure has also been intensively studied, involving the influences of intercritical annealing temperature [9][10][11], intercritical annealing time [10,12] and alloying elements [13][14][15].…”

Deformation-Induced Phase Transformations

“…The present Special Issue includes two review papers [1,2] and seven scientific papers [3][4][5][6][7][8][9] covering compositional, microstructural, and crystallographic aspects of deformation-induced phase transformations in titanium alloys [2,5,6], steels [3,4,[7][8][9], and shape memory alloys [1].…”

“…However, to date, the clear understanding of various factors influencing the occurrence of this event remains elusive as a result of the complexity of their different interactions. Both material-dependent parameters, such as a stacking fault energy of austenite in steels and β phase stability in Ti alloys [2,5], as well as external/loading conditions (temperature, uniaxial tensile, plane strain compression, cyclic loading, high pressure torsion) [2,[4][5][6][7] are examined in this Special Issue.…”

Analysis of Plastic Deformation Instabilities at Elevated Temperatures in Hot-Rolled Medium-Mn Steel

“…Most of studies concerning medium-Mn sheet steel are focused on production aspects. However, factors affecting the processing of steel sheets are rarely analyzed [1,4,5].…”

“…Both types of instabilities may lead to the occurrence of numerous cracks during forming processes or delayed cracking after deep drawing [9]. Medium-Mn steels that are produced by cold-rolling and subsequent intercritical annealing may show a discontinuous yielding behavior [5,7,10]. However, in the case of hot-rolled grades, this effect does not occur [11,12].…”