Recrystallization behavior of the fourth generation single crystal superalloy based on different original microstructure preset strain

Abstract

The specimens of the fourth generation single crystal superalloy after heat treatment and at as-cast state were indented and annealed in vacuum at 1100, 1150, 1200, 1250, 1300℃ and 1340℃, respectively. The recrystallized microstructures of the alloy were examined by optical microscopy (OM), scanning electron microscopy (SEM) and electron back scattering diffraction (EBSD). The results show that cellular recrystallization (CRX) occurs in the standard heat treatment samples and as-cast samples after annealing treatment at 1100, 1150℃ and 1200℃. Mixed recrystallization occurs in standard heat treatment samples and as-cast samples after annealing treatment at 1250℃. Equiaxed recrystallization (ERX) develops when the standard heat treatment samples are annealed treatment at 1300℃, while mixed recrystallization occurs in as-cast samples at same condition. ERX develops when these two samples are annealed at 1340℃. The recrystallized layer depth of these two samples increases with the increase of annealing treatment temperature and the depth of standard heat treatment samples is obviously larger than that of as-cast samples.The recrystallized grain of standard heat treatment samples easily grows up at same condition. The interface between the recrystallization grain and original grain is low angle boundary and high angle boundary, while the interface between adjacent recrystallization grains is low angle boundary, high angle boundary, and twinning boundary. It can be inferred that the formation of twins can play an important role in the process of recrystallization.

Keywords

• single crystal superalloy
• original microstructure
• recrystallization
• grain boundary