Patent ID: 7763129

Claim:
A method of controlling the average grain size of a worked articled formed of a gamma-prime precipitation strengthened nickel-base superalloy having a gamma-prime solvus temperature, the method comprising the steps of: consolidating a powder of the gamma-prime precipitation-strengthened nickel-base superalloy to form a billet having a sufficiently fine grain size to achieve superplasticity of the superalloy during a subsequent working step; working the billet at a temperature below the gamma-prime solvus temperature of the superalloy so as to form the worked article, wherein the billet is worked above the superplastic regime in the non-superplastic or marginally superplastic regime while maintaining strain rates above a lower strain rate limit of 0.001 sec −1 to control the average grain size of the worked article and below an upper strain rate limit to avoid critical grain growth, and so that strains within the billet are maximized on the basis of strain energy imparted to the billet during the working step, wherein the strain energy is estimated by strain rate within the billet raised to an exponential value.