Temperature and grain size dependent plastic instability and strain rate sensitivity of ultrafine grained austenitic Fe-14Cr-16Ni alloy

In this study temperature and grain size dependent plastic instability and strain rate sensitivity (SRS) were investigated for coarse grained (CG) and ultrafine grained (UFG) austenitic Fe-14Cr-16Ni alloys. As tensile testing temperature increased from 20 to 200 °C, UFG alloys exhibited much more prominent decrease of uniform strain compared with CG counterparts. Transmission electron microscopy (TEM) analysis of deformed UFG alloys revealed temperature dependent evolution of microstructures. Through grain refinement, the SRS of Fe-14Cr-16Ni alloy increased and activation volume decreased, which may be related to the interactions of dislocations with grain boundaries. The SRS of UFG alloys exhibited greater temperature dependence than CG alloys.