On the Coupling between Recrystallization and Precipitation Following Hot Deformation in a γ-γ′ Nickel-Based Superalloy
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Postdynamic recrystallization and γ′ precipitation during cooling from γ′ supersolvus temperature after hot compression were studied in the AD730 (AD730 is a trademark of Aubert et Duval Company in Paris, France) γ-γ′ nickel-based superalloy. Emphasis was on not only both phenomena as distinct mechanisms but also on their mutual influence in terms of physical mechanisms. The growth of γ′ precipitates is hastened in the unrecrystallized grains compared to the recrystallized ones. This could possibly be attributed to the higher dislocation content acting as high-diffusivity paths. Postdynamic recrystallization is not prevented by Smith–Zener pinning of the recrystallization front by the γ′ precipitates. Instead, the recrystallization front dissolves γ′ precipitates, which then reprecipitate discontinuously or continuously and coherently with the surrounding γ matrix in the recrystallized grains.
This project was carried out in the framework of the OPALE Industrial Chair funded by the French National Agency for Scientific Research ANR and the Safran Group. The Safran Aircraft Engines Company supplied the hot-compression samples. The authors are grateful for the help of G. Fiorucci in the development of the experimental setup for slow cooling and quenching at CEMEF.
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