Modeling microstructural evolution and the mechanical response of superplastic materials

摘要

A model has been developed that accounts for grain growth during, superplastic flow and its subsequent influence on stress-strain-strain rate behavior. These studies are experimentally based and have involved two different types of superplastic materials -- a quasi-single phase metal (Coronze 638) and a microduplex metal (ultrahigh-carbon steel - UHCS). In both materials the kinetics of strain-enhanced grain growth have been studied as a function of strain, strain rate and temperature. An equation for the rate of grain growth has been developed that incorporates the influence of temperature. The evolution of the grain size distribution during superplastic deformation has also been investigated. Our model integrates grain growth laws derived from these studies with two mechanism based, rate dependent constitutive laws to predict the stress-strainstrain rate behavior of materials during superplastic deformation. The influence of crain size distribution and its evolution with strain and strain rate on the stress-strain-strain rate behavior has been represented through the use of distributed parameters. The model can capture the stress-strain-strain rate behavior over a wide range of strains and strain rates with a single set of parameters. Many subtle features of the mechanical response of these materials can be adequately predicted. (ERA citation 18:026727)