High-temperature diffusion-controlled creep behavior of the Zn-22% Al eutectoid alloy tested in torsion

Abstract

Torsion testing was carried out on Zn-22% Al eutectoid alloy and covered a range of strainrates between 4.4 × 10 −5 S −1 and 4.2 × 10 −1 s −1, temperatures between 413K and 533 K and grain sizes between 0.8 × 10 −4 cm and 3.5 × 10 −4cm. Within the range of strain-rates, temperatures and grain sizes investigated, four rate-controlling deformation mechanisms are found operative and are identified as Coble creep, Nabarro-Herring creep, superplastic creep and dislocation climb creep, respectively. The ranges of manifestation of each mechanism in terms of stress, strain-rate, temperature and grain size, are determined. The four mechanisms are shown to relate to each other and new correlation form based on the newly proposed { AM} parameter is developed. Furthermore, it is shown that for the high-temperature diffusion-controlled deformation mechanism, the value assumed by the { AM} parameter, completely and uniquely identifies the rate-controlling deformation mechanism.