EFFECT OF TEMPERATURE ON THE MECHANICAL-PROPERTIES OF MECHANICALLY-ALLOYED MATERIALS AT HIGH-STRAIN RATES

The superplastic properties of several mechanically-alloyed materials, including IN9021, IN9052, IN905XL and 15 vol.% SiCp/IN9021, have been characterized. The tensile elongation to failure, strain rate sensiti vity and activation energy are found to be dependent upon the testing temperature. Specifically, marked changes in these properties are clos ely related to incipient melting points in the materials. These observ ations confirm the suggestion that the presence of a small amount of l iquid phase at interfaces and grain boundaries not only enhances the s train rate for superplasticity, bur also has a strong influence on the deformation mechanisms. When the amount of liquid phase increases, as a result of increasing temperature, the expected observation is noted , i.e. the presence of the liquid phase degrades the material properti es. A model is proposed to explain the experimental observations.