Influences of Thermal Martensites and Grain Orientations on Strain-induced Martensites in High Manganese TRIP/TWIP Steels

Fayun Lu 1),Ping Yang 1),Li Meng 1),Fenge Cui 1) and Hua Ding 2) 1) School of Materials Science and Engineering,University of Science and Technology Beijing,Beijing 100083,China 2) College of Materials and Metallurgy,Northeastern University,Shenyang 110004,China

摘 要：Strain-induced martensites in high manganese TRIP/TWIP steels were investigated in the presence of thermal martensites and under the influence of austenitic grain orientation by X-ray diffraction（XRD）,scanning electron microscopy（SEM） and electron backscattered diffraction（EBSD）.Before deformation,the morphology of α’-M depended mainly on the number of variants and growing period.Regardless of martensite morphologies and deformation,the Kurdjumov-Sachs（K-S） orientation relationships always maintained.The 6 α-M variants formed from a plate of ε-M were of 3 pairs of twins with a common axis <110> α’ parallel to the normal of {111} γ habit plane to minimize transformation strain.When α’-M could be formed only by deformation,it nucleated at the intersection of ε-M variants and grew mainly in thick ε-M plates.Thick ε plates promoted significantly the α’-M and weakened the influence of grain orientations.During tension,the transformation in <100>-oriented grains was observed to be slower than that in <111>-oriented grains.Deformation twins promoted ε-M formation slightly and had no apparent effect on α’-M.Deformation increased the number of ε-M variants,but reduced that of α’-M variants.

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