Fig. 1 SEM micrographs of marked areas on the surface of specimen before deformation

Fig. 2 Statistic results of the orientation relationships between the austenite and thermal α′-M: a, b distribution of misorientation angle before and after deformation; c, d rotation axis of the three ORs mentioned above before and after deformation; e, f ORs before and after deformation; g, h distribution of rotation axis showed in stereographic projection triangle before and after deformation

Fig. 3 Statistic results of the orientation relationships between the austenite and deformation-induced α′-M: a distribution of misorientation angle; b rotation axis of the three terms mentioned above; c orientation relationship; d distribution of rotation axis showed in stereographic projection triangle

Fig. 4 EBSD orientation maps and the orientations of the austenitic grains and α′-M variants: a orientation map of α′-M before deformation (colors α′-M variants, gray austenite and ε-M); b magnifying orientation map of the region inside square in a (colors austenite with twin relationship, gray α′-M and ε-M); c orientation map of α′-M and austenite (orange and light purple austenite (the same as b), other (colors α′-M, gray ε-M); d the inverse pole figure for the TA direction of austenitic grains investigated in this study; e, f the inverse pole figure of α′-M variants with N-W relationship and K-S relationship, respectively