Evaluation of microstructural instability during the differential strain rate test of a superplastic alloy

Research paper by B. P. Kashyap, G. S. Murty

Indexed on: 01 Jul '83Published on: 01 Jul '83Published in: Journal of Materials Science


Stress (σ)-strain rate (\(\dot \varepsilon \)) data of banded and elongated grain microstructures of the Pb-Sn eutectic alloy were analysed over 298 to 443 K to evaluate microstructural instability during differential strain rate tests in the superplastic region. With reference to a stable equiaxed microstructure exhibiting uniqueσ-\(\dot \varepsilon \) relation, banded structure is more susceptible to strain hardening while the elongated grain microstructure exhibits either strain softening or strain hardening depending on the test temperature. This flow behaviour is considered in terms of a change in grain size, represented by the cube root of the grain volume. Activation energy for grain growth calculated from the differential strain rate test data indicates that the activation energy depends on strain rate and type of microstructure.