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Published online by Cambridge University Press: 22 February 2011
The tensile behavior of IN90211 was characterized at strain rates between 0.0001/sec and 340/sec at temperatures between 425 and 475 °C. At strain rates below 0.1/sec, the strain rate sensitivity m is about 0.027, with corresponding low elongation (<100%). At strain rates above 0.1/sec, the strain rate sensitivity increases to 0.26. A maximum elongation of 500% was obtained at 475 °C at a strain rate of 2.5/sec. Grain boundary sliding and rotation was observed on the highly elongated specimens and fracture surfaces exhibited intergranular fracture. Experimental data in the high strain rate regime (superplastic) revealed the existence of a temperature dependent threshold stress that seemed unrelated to the low stress deformation regime. This result is consistent with stress relaxation experiments. These threshold stresses are generally lower than those typically observed in other oxide dispersion strengthened (ODS) alloys. This observation is not expected from conventional superplastic creep theory.