Strong and ductile medium Mn steel without transformation-induced plasticity effect

Abstract

The conventional alloy design of medium Mn steel is to optimize the transformation-induced plasticity (TRIP) effect. Here we show that a dual-phase heterogeneous structure is sufficient to develop a medium Mn steel with high yield strength ( ∼ 1.2 GPa) and large uniform elongation ( ∼ 14.5%). The ultra-high strength is contributed by high back-stress while the large ductility is induced by strain-gradient plasticity and back-stress hardening, both of which are inherent to dual-phase heterogeneous structure. TRIP effect is suppressed during plastic deformation. Therefore, medium Mn steel can be strong and ductile by engineering dual-phase heterogeneous structure without resorting to TRIP effect. IMPACT STATEMENTWe demonstrate that medium Mn steel can be strong and ductile by engineering dual-phase heterogeneous structure without resorting to the conventional transformation-induced plasticity (TRIP) effect. ARTICLE HISTORY

Strong and ductile AZ31 Mg alloy with a layered bimodal structure

“…Pioneering studies have shown that pure Ti with a heterogeneous lamella structure can unite UFG strength and coarse-grain ductility 19 . Such combinations of high strength and good ductility were also demonstrated recently in an interstitial free (IF) steel 20 and a Mn steel 21 . Therefore, the present study is aimed to produce a layered bimodal grain structure in Mg alloys and address the effect of bimodal structures on mechanical properties.…”

On the Factors Governing Austenite Stability: Intrinsic versus Extrinsic

“…The partitioned stress/strain is a vital extrinsic factor in affecting the austenite stability and is correlated to the strength of adjacent phases. If the partitioned stress does not effectively increase the mechanical interaction energy to help the austenite grains overcome the nucleation barrier, the TRIP effect resulting from the martensitic transformation may be suppressed during the plastic deformation [ 205 ]. In this case, the improvement of work hardening behaviors assisted by the TRIP effect is missed, leading to the relatively low work hardening rate.…”

Carbon content-tuned martensite transformation in low-alloy TRIP steels

“…Medium- and high- Mn steels are the most promising candidates with the TRIP effect and thus show excellent mechanical properties. The strengthening mechanism for those materials is based on the transformation of the metastable austenite induced by deformation, i.e., the face-centered cubic (FCC) structured γ-phase characterized by a high work hardening capacity to achieve very high strength together with exceptional ductility 1 to martensite characterized by the hexagonal close-packed (HCP) ε-phase and/or body-centered cubic (BCC) α′-phase 2–7 .…”