The rate controlling deformation mechanism in high strain rate superplasticity

An analysis of high strain rate superplasticity data shows a change in activation energy with particle size. The result is explained on the basis of change of rate controlling mechanism with second phase particles. The prediction of diffusional relaxation models agrees well with the experimental results. The temperature for onset of high strain rate superplasticity in mechanically alloyed aluminum and nickel base alloys can also be predicted by diffusional relaxation models. These concepts can be used to construct a superplastic mechanism map.