A review of the processing, microstructure and property relationships in medium Mn steels

Abstract

Medium Mn steels are an emerging class of 3rd generation advanced high-strength steels. These steels have received significant attention due to their high strengths, large ductilities and also lower cost compared to their predecessor high Mn Twinning Induced Plasticity (TWIP) steels. Additionally, medium Mn steels have been found to exhibit TWIP and/or Transformation Induced Plasticity (TRIP) effects which can be harnessed to give a high strain hardening rate. Many thermomechanical processing concepts in the literature have been developed, producing multiple microstructure types with differentmechanical properties. The present review therefore aims to summarise the current knowledge of medium Mn steel alloy design especially on the processing, microstructure and property relationships in medium Mn steels. It complements the review of Sun et al. [Physical metallurgy of medium-Mn advanced high-strength steels, Int Mater Rev. 2023.], written independently and in parallel, which focusses more on the phase interfaces and thermodynamics.

Cracking Behavior and High-Temperature Thermoplastic Analysis of 09CrCuSb Steel Billets

“…It can be seen that the increase of alloy elements means that the transformation time of proeutectoid ferrite during the cooling process is advanced due to the increase of Ae3 temperature [33,34]. It also means that during the cooling process, the formation of ferrite will happen before it would in steel [35]. Therefore, when the slab enters the straightening machine during continuous casting, the surface temperature due to the effect of reheating should return to above 800 °C.…”

“…It can be seen that the increase of alloy elements means that the transformation time of proeutectoid ferrite during the cooling process is advanced due to the increase of Ae3 temperature [33,34]. It also means that during the cooling process, the formation of ferrite will happen before it would in steel [35]. Therefore, when the slab enters the straightening machine during continuous casting, the surface temperature due to the effect of reheating should return to above 800 • C. The expansion of the two-phase region leads to the extension of the insulation time of the billet in the two-phase region, and proeutectoid ferrite precipitation is also promoted when the grain boundary satisfies certain thermodynamic conditions.…”

Crystal Plasticity Finite Element Modeling of the Influences of Ultrafine-Grained Austenite on the Mechanical Response of a Medium-Mn Steel

“…Mechanical twinning, a common phenomenon in many metallic materials, including medium-Mn, facilitates material deformation through the simultaneous cooperative shear of numerous planes, enabling large shear strains. Both TRIP and TWIP significantly increase the work hardening rate and strengthen the material [4,[21][22][23]. Previous studies on medium-Mn indicate that mechanical twinning was observed at an early age of 8% in engineering strains, and it is assumed that austenite did not transform before this strain [6].…”

Superior Yield Strength and High‐Tensile‐Toughness Matching of Medium‐Mn Steel with Gradient Structure Developed by Cyclic Torsion

“…As potential candidates in new advanced high-strength steels, medium-Mn steels are particularly attractive for manufacturing energy-absorbing parts of automotive body in white, because they possess an excellent strength-ductility combination and have a low cost. [1,2] Despite these attractive properties, the practical application of this steel grade is hindered by its relatively low yield strength (YS), which is ascribed to the soft matrix after intercritical annealing. [3,4] Considering the high safety standards and weight reduction in the future automotive industry, medium-Mn steels with high YS (>850 MPa) and low density should be designed.…”