Hot Deformation Behavior and Development of Constitutive Equations on a Novel γ-γ/ Ni-base Superalloy: AD730

Abstract

In this work, hot deformation behavior and microstructural evolution for a novel Ni-base superalloy, AD730, were analyzed using a hyperbolic sine constitutive equation. The hot compression tests were carried out at a wide range of temperatures (950oC-1200oC) and strain rates (0.001-1 s-1). The modeling was done at the overall deformation conditions, and then the obtained important constitutive parameters, i.e., n and Q, were calculated to be 5.44 and 820.26 kJ/mol, respectively. Microstructural evolution showed two distinct domains at higher temperatures (1100oC, 1150oC, and 1200oC) and lower ones (950oC, 1000oC, and 1050oC) accomplished by dynamic recrystallization (DRX) and non-DRX behavior due to absence and presence of γ/ particles, respectively. Furthermore, the constitutive equations were analyzed based on both separated temperature domains. The obtained parameters from this approach demonstrated better results as compared with the literature, i.e., the parameters of n and Q were calculated to be 8.60 and 1160.45 kJ/mol at the lower domain, in contrast with 3.69 and 468.32 kJ/mol which were at higher ones. Additionally, the stress prediction data based on correlation coefficient factor (R2) presented the best reliable prospective at two separated domains as 0.994, as compared with overall conditions prediction with 0.963. It was found that hot working of AD730 alloy as well as flow stress can be essentially affected by the γ/-phase. Therefore, the hot deformation behavior of AD730, as a γ/-containing superalloy, should be performed at identified domains considering the solution temperature of γ/-phase.