5%Mn鋼の加工誘起マルテンサイト変態に伴う引張変形中のオーステナイトの集合組織変化

抄録

Medium manganese steels, containing 3~10 mass% of Mn, are considered promising as the 3rd generation high strength steel. In this study, in situ neutron diffraction experiments were conducted during uniaxial tensile deformation for Fe-4.91Mn-0.092C (mass%). The primary aim was to investigate the change of austenite texture accompanied with the deformation induced martensitic transformation (DIMT). It was observed that grains oriented <001> towards the tensile direction tend to persist during the deformation. Moreover, the fraction of <001> oriented grains increases due to crystal rotation caused by dislocation slip. Grains with <111> towards the tensile direction are consumed more rapidly than those with <001>. These observations are qualitatively reproduced by visco-plastic self-consistent model, additionally considering DIMT to ε martensite. Although ε martensite was not identified in the diffraction pattern obtained in this study, a previous microstructural study indicated the γ→ε→α’ type DIMT for the same material. In contrast, it is known that in low alloyed TRIP steels subjected to tensile deformation, grains with <111> tend to survive, where γ→α’ type DIMT occurs. Based on the results of this study, the orientation that persists after tensile deformation can distinguish between the DIMT mechanisms: γ→ε→α’ or γ→α’ type.