DEFORMATION BANDS ON SURFACE OF NIOBIUM SINGLE CRYSTALS DURING CYCLIC DEFORMATION
铌单晶循环变形过程中的表面形变带

The surface morphology of niobium single crystals with 321]and 110] orientations during the deformation has been observed. Specimens withround cross section have been cycled to the saturated stage and the surface topog-raphy of rumpled bands has been observed using optical and scanning electron mi-croscope. In the present paper, the term of "deformation band", which is defferentfrom the kink band with special orientation, is used to define the rumpled band ofmaterial that has undergone inhomogenous plastic deformation. According to thedetailed topography, the deformation bands have been further subdivided into fivetypes and their formation process has been discussed. The deformation bands lie onthe plane of approximately 45° to the loading axis, i. e. the plane of the maxi-mum shear stress, which indicates that the macroscopic state of stress plays an im-portant role on the formation of deformation bands.