A novel medium Mn steel of composition Fe-12Mn-4.8Al-2Si-0.32C-0.3V was manufactured with 1.09 GPa yield strength, 1.26 GPa tensile strength and 54% elongation. The thermomechanical process route was designed to be industrially translatable and consists of hot and then warm rolling followed by a 30 min intercritical anneal. The resulting microstructure comprised of coarse elongated austenite grains in the rolling direction surrounded by necklace layers of fine austenite and ferrite grains. The tensile behaviour was investigated by in-situ neutron diffraction and the evolution of microstructure studied with Electron Backscattered Diffraction (EBSD). It was found that the coarse austenite grains contributed to the first stage of strain hardening by transforming into martensite and the fine austenite necklace grains contributed to the second stage of strain hardening by a mixture of twinning and transformation induced plasticity (TWIP and TRIP) mechanisms. This hierarchical deformation behaviour contributed to the exceptional ductility of this steel.

制造了具有Fe-12Mn-4.8Al-2Si-0.32C-0.3V成分的新型中锰钢，其屈服强度为1.09 GPa，拉伸强度为1.26 GPa，延伸率为54％。热机械工艺路线设计为可工业转换，由热轧然后热轧，然后进行30分钟的临界退火组成。所得的显微组织由沿轧制方向的粗长奥氏体晶粒组成，并由细奥氏体和铁素体晶粒的项链层围绕。通过原位中子衍射研究了拉伸行为，并通过电子背散射衍射（EBSD）研究了微观结构的演变。发现粗奥氏体晶粒通过转变成马氏体而有助于应变硬化的第一阶段，而细奥氏体项链晶粒通过孪生和相变诱导塑性（TWIP和TRIP）的混合作用而有助于应变硬化的第二阶段。这种分层的变形行为有助于该钢的出色延展性。