Characteristics of second generation microbands in cold-rolled copper

Shear Localization in Crystallographic Bands in Rolled Copper and Brass

“…The reason for this instablity seems quite clear: when formed the walls of the microbands do not consist of geometrically necessary dislocations [10] since they do not separate areas with different lattice orientations (the concentrated slip on slip planes parallel to the walls does not per se create any orientation change in the material in the microbands, cf. [2]). According to the density of second-generation microbands observed by TEM the microbands only account for about 10% of the strain in the grains with microbands (the LWD grains) [2], but because of the instability this is obviously an underestimate.…”

“…[2]). According to the density of second-generation microbands observed by TEM the microbands only account for about 10% of the strain in the grains with microbands (the LWD grains) [2], but because of the instability this is obviously an underestimate. Surface observations [9] have been quoted to indicate that the microbands account for the majority of the strain in a range of moderate rolling reductions.…”

“…The investigation of the second-generation microbands is hampered by their structural instability as described in detail by Ananthan et al [2,7]. It is a very common observation in TEM investigations that parts of microbands have vanished.…”

“…It is a very common observation in TEM investigations that parts of microbands have vanished. Ananathan et al [2] suggest that the microbands are eroded by subsequent slip processes, while Hatherly [9] suggests that the microbands disappear during thin-foil preparation. The reason for this instablity seems quite clear: when formed the walls of the microbands do not consist of geometrically necessary dislocations [10] since they do not separate areas with different lattice orientations (the concentrated slip on slip planes parallel to the walls does not per se create any orientation change in the material in the microbands, cf.…”

“…Two different types of shear localization have been observed in fcc materials rolled to moderate reductions: microbands (in our terminology second-generation microbands) in copper [1,2], aluminium-magnesium [3] and nickel [4] and bundles in brass and other fcc alloys with low stacking fault energy [5,6]. Both microbands and bundles are thin (0.5 pm or less) plates or bands closely parallel to {Ill} in which the strain (slip parallel to the plane of the band) is far greater than in the surrounding material.…”