Changes in surface topography during the early stage of cyclic deformation of b.c.c. iron-alloy single crystals

Abstract

In cyclic dcformation of 5 wt.% aluminium—iron and 5 wt.% germanium—iron single crystals, a remarkable homogenization of strain has been observed in the rapid-hardening region, which appears as an almost complete annihilation of original surface slip traces formed during the first half-cycle. This, together with a similar result on 3 wt.% silicon-iron single crystals reported previously, provides substantial support to a previous proposition that the surface-smoothing effect is present in all materials which fulfil the following two requirements. (1) On unidirectional deformation, slip bands are formed which are composed mainly of screw dislocations, and work-hardening within them is moderate. (2) There exists a plastic anisotropy high enough to cause a variation of slip planes operative in tension and compression.

Furthermore, the experimental result that such an effect was totally absent in pure iron, which does not satisfy the requirements completely, suggests that they are necessary conditions for the effect.