The superplastic behaviour of nickel based superalloy NK17CDAT( Astroloy) has been studied using torsion testing. The evolutions of stress and average grain size are found to follow the same classical behaviour as other nickel based alloys under similar conditions. The superplastic flow is characterised by a strain rate sensitivity exponent of 0·5 and a grain size sensitivity exponent of 3. Modelling of this alloy can be considered using a combination of microscopic mechanisms, namely, those of Gittus, Coble, and dislocation glide–climb.
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