Article. Cavendish Laboratory, Cambridge. 1951. pp. 747-753.
An attempt is made here to explain the observed phenomena in the yielding and ageing of mild steel, described in two previous papers, in the general terms of a grainboundary theory. On this hypothesis, a satisfactory explanation of the variation of the lower yield point with grain size may be developed. It is shown that strain-ageing must involve two processes: a healing of the grain-boundary films, coupled with a hardening in the grains themselves A discussion of the possible nature of the grain-boundary film is also undertaken.