Partial melting at interfaces and graln boundaries for high-strain-rate superplastic materials

The present paper describes partial melting at matrix/reinforcement interfaces and grain boundaries for high-strain-rate superplastic metallic materials. It is suggested from the mechanical testing results that partial melting is associated with the deformation mechanisms of the high-strain-rate superplasticity. DSC measurements and TEM observations reveal that solute additions are segregated at the interfaces and grain boundaries, so that partial melting occurs at elevated temperatures. This supports the concept of the accommodation helper mechanisms such as the accommodation by a liquid phase. However, when a liquid phase is continuous and thick, intergranular decohesion is caused at liquid interfaces and grain boundaries. Therefore a discontinuous and thin liquid phase is required both to play a vital roll as an accommodation helper and to limit intergranular decohesion.