Hot Deformation Behavior and Development of Constitutive Equations on a Novel γ-γ/ Ni-base Superalloy: AD۷۳۰

In this work, hot deformation behavior and microstructural evolution for a novel Ni-base superalloy, AD۷۳۰, were analyzed using a hyperbolic sine constitutive equation. The hot compression tests were carried out at a wide range of temperatures (۹۵۰ºC-۱۲۰۰ºC) and strain rates (۰.۰۰۱-۱ s-۱). 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 ۵.۴۴ and ۸۲۰.۲۶ kJ/mol, respectively. Microstructural evolution showed two distinct domains at higher temperatures (۱۱۰۰ºC, ۱۱۵۰ºC, and ۱۲۰۰ºC) and lower ones (۹۵۰ºC, ۱۰۰۰ºC, and ۱۰۵۰ºC) 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 ۸.۶۰ and ۱۱۶۰.۴۵ kJ/mol at the lower domain, in contrast with ۳.۶۹ and ۴۶۸.۳۲ kJ/mol which were at higher ones. Additionally, the stress prediction data based on correlation coefficient factor (R۲) presented the best reliable prospective at two separated domains as ۰.۹۹۴, as compared with overall conditions prediction with ۰.۹۶۳. It was found that hot working of AD۷۳۰ alloy as well as flow stress can be essentially affected by the γ/-phase. Therefore, the hot deformation behavior of AD۷۳۰, as a γ/-containing superalloy, should be performed at identified domains considering the solution temperature of γ/-phase.

Keywords:

AD۷۳۰ , Hot deformation , DRX , Hyperbolic sine modeling , γ/ phase