High strain rate superplasticity in metal matrix composites: the role of Load transfer

摘要

It is well established that metal matrix composites may exhibit high strain rate superplasticity (HSR SP) but the measured activation energies are higher than anticipated for lattice self-diffusion or grain boundary diffusion in the matrix alloys. It is proposed that the occurrence of load transfer introduces an additional dependence on temperature which must be included in any attempt to estimate the true acti- vation energy for flow, Q. Experimental data are analyzed for four metal matrix composites and it is demonstrated that, by incorporating load transfer for each material, Q may be reduced to a value close to that anticipated for grain boundary diffusion up to testing temperatures within a few degrees of the incipient melting temperature.