Transmission Kossel Study of the Structure of Cold-Rolled Iron and its Nucleation Behaviour

By examining thin sections and by use ofthe more strongly absorbed Ti K α radiation ratherthan Fe K α radiation it was found possible to obtainuseful transmission Kossel patterns from ironthat had been deformed 40% by rolling. Examinationof the as–deformed material showed large misorientationsin all the matrix grains (20–54°) and manyof the grains showed deformation bands where theorientation changed rapidly (up to 15° over distancesof 50 μm). On annealing the material recrystallizedby strain-induced boundary migrationwith all the invaded grains being those with (111)parallel to the rolling plane. Only one examplewas found of new grain formation by mutual invasionacross a deformation band, the main nucleation modepreviously observed in aluminum deformed 40% bycompression. The difference between the two examplesappears to arise from the smaller misorientationsof the deformation bands in rolled iron.