(A) study of plastic deformation for several iron alloys and titanium alloys

Abstract

Kim-Ree``s theory for plastic deformation was applied to Fe alloys and Ti alloys and Ti alloys. For Fe alloys, the flow equations of stress f vs. -ln (strain rate $\dot{s}$) were obtained. Generally only one kind of grain boundary flow units appeared for Fe alloys. It was found that the relationship of ln $β^{-1}$ vs. carbon content [C] is linear for hot-rolled steel, where β is a factor proportional to the relaxation time of the flow units, and [C] is the carbon contents in the sample. For other Fe alloys, the strain rate sensitivity m defined by m=dln f/dln $\dot{s}$ was also calculated by Kim-Ree``s theory, the theoretical m values were compared with experimental data. The result was satisfactory. The flow equations were also obtained for Ti alloys. For the samples with different grain sizes having the same composition, the flow equations were obtained, and the strain rate sensitivity m was calculated from the Kim-Ree theory by using the parameters included in the theory with a good result compared with experiment. And, for these samples, the relationship of ln $β^{-1}$ vs. x(x: grain size) was also obtained, and it was found that the relationship is true as predicted by Kim-Ree``s theory. The activation enthalpies for plastic deformation of Fe alloys and Ti alloys were about 60 kcal/g.atom and about 31 kcal/g.atom, respectively. These values are in good agreement with the activation enthalpies of self-diffusion of Fe and Ti. This result is self-consistant with the flow mechenism proposed by Kim and Ree, and by others.