Characterization and 3D finite element modelling of TRIP effect in a medium manganese steel with nano-precipitates

Highlights: • Mechanical properties of a 1 GPa-grade medium maganese steel was ensured by the combination of intercritical annealing and quasi-austempering process. • More pronounced martensitic transformation of the large aspect ratio austenite prevented the nucleation and coalescence of microvoids. • The alleviation of the localized stress concentration was quantitatively demonstrated by the 3D micromechanical analysis. An ultra-low carbon Cu-rich medium manganese steel has been investigated through intercritical annealing and subsequent quasi-austempering to evade grain boundary embrittlement and enhance the resistance against cracking. The normal tempering treatment after intercritical annealing and quenching was conducted for comparison, which showed relatively lower amount of retained austenite and dispersion number density of co-precipitates than the quasi-austempered counterpart. The large aspect ratio metastable austenite in the quasi-austempered sample provided sustainable transformation-induced plasticity (TRIP) effect during deformation, which efficiently alleviated the localized stress concentration. A three-dimensional finite element modelling in virtue of the representative volume elements method was utilized to reveal the relationship between the typical microstructure and the mechanical properties. It was shown that the quasi-austempered sample exhibited lower strain energy value nearby the grain boundaries than the normally tempered one after initial deformation.