Deformation Mechanism of High-Mn Austenitic Steels with Fully Recrystallized Ultrafine Grained Structures
We have found recently that high-Mn austenitic steels with fully recrystallized ultrafine grained (UFG) structure having a mean grain size of about 0.4 μm could be fabricated without severe plastic deformation.The UFG material showed high strength and large ductility,but the reason for such good mechanical properties was still unclear.In this study,we investigated the mechanical properties and deformation mechanism of the UFG high-Mn austenitic steels (so-called twinning-induced plasticity (TWIP) steels).Specimens having various ultrafine grain sizes were fabricated through thermomechanical processes designed by ourselves.Tensile tests under various conditions,microstructural characterization by SEM-ECCI and EBSD,and measurement of dislocation density by XRD were carried out for the coarse grained and UFG specimens.From the results of the tensile test of the UFG high-Mn austenitic steels,we found that stress-strain curves showed yield-drop phenomena,and the yield stress was higher than the value predicted by the Hall-Petch relationship.From the results of microstructural characterization,it was found that the grain size dependencein the quantity of deformation twins was different between the coarse grained structure and the UFG structure.Furthermore,from the results of XRD,the dislocation density rapidly increased just after the yield drop in the UFG structure.From these results,it became clear that the deformation mechanism of the UFG structure is different from that of the coarse grained structure.At present,we consider that grain boundary acted as a source of dislocations and twins in the UFG high-Mn austenitic steels.
high-manganese(Mn) steel ultrafine grained material(UFG) grain boundaries
KITAMURA Hiroki BAI Yu TIAN Yanzhong SAHA Rajib SHIBATA Akinobu TSUJI Nobuhiro
Department of Materials Science and Engineering, Graduate School of Engineering,Kyoto University, Yo Elements Strategy Initiative for Structural Materials(ESISM), Kyoto University,Yoshida Hommachi, Sak Department of Materials Science and Engineering, Graduate School of Engineering,Kyoto University, Yo Department of Materials Science and Engineering, Graduate School of Engineering,Kyoto University, Yo
国际会议
成都
英文
210-213
2016-11-16（万方平台首次上网日期，不代表论文的发表时间）