The qualitative behavior of the dislocation density, the residual long-range internal stresses, and the volume fraction of cell-wall material, were studied. It was noted that, at first, there was a rapid increase in the dislocation density and in the residual long-range internal stresses; well into stage III. This was followed by a slowing down, or even a decrease, in their values in the transition range between stages III and IV. These 2 parameters then increased in stage IV, and exhibited a slight maximum or a levelling-off in stage V, respectively. The volume fraction of the cell-wall material decreased markedly after reaching a maximum at the beginning of stage IV, and remained constant at higher deformations. The rapid increases in the above parameters at small deformations, and their tendency to level off in stage IV had already been reported. However, the later slowing-down or decrease in these 2 quantities, and the levelling-off of the volume fraction of cell-wall material with the onset of stage IV, were essential features of a proposed new micro-mechanism for stage-IV work hardening.

Stage-IV Work-Hardening in Cell-Forming Materials – I. M.Müller, M.Zehetbauer, A.Borbély, T.Ungár: Scripta Materialia, 1996, 35[12], 1461-6