2013 Volume 54 Issue 4 Pages 512-519
Ni base superalloy is one of the representative heat resistant materials for high temperature environment in various industrial applications. As for cast and wrought material, thermo-mechanical processing during hot forging has a significant role to control and optimize crystal grain structure in order to attain required critical properties. The essential deformation and dynamic recystallization behavior of Ni base superalloy, Alloy718 during hot forging were revealed through hot compression tests and quantitative relations among various parameters that were available for numerical calculation were derived. Dynamically recrystallized grain diameter depended on temperature, strain rate and was independent of initial grain diameter and strain. And the grain diameter was expressed as a function of the temperature compensated strain rate, i.e., Zener–Hollomon parameter quantitatively. Avrami-type equation was available for comprehensive and quantitative expression of dynamic recrystallization transition tendency. And the fraction of dynamic recrystallization was a function of the given strain and the strain for 50% recrystallization which depended on the initial grain diameter and Zener–Hollomon parameter.