Superplastic behaviour of powder-consolidated nickel-base superalloy IN-100

The superplastic behaviour of the powder-consolidated nickel-base superalloy IN-l00 has been determined in the temperature range 1193–1311 K and over a range of strain rates from ∼ 10⁻⁵ to ∼ 10⁻¹ S⁻¹. The results showed that characteristically three regimes of behaviour occurred. At low strain rates the strain-rate sensitivity was low and work hardening occurred throughout the tests. At intermediate and high strain rates the strain-rate sensitivity index m was >0.6 and work softening was observed. At the highest strain rates m fell to ∼0.2. The activation energy of deformation was high and greater than that expected for volume diffusion. At high strain rates the deformation appeared to be controlled by dislocation creep. It was not possible to identify unequivocally the deformation mechanism in the superplastic regime although the evidence favoured a combination of grain-boundary sliding and Coble creep.