基于不同原始组织预设变形第四代单晶高温合金的再结晶行为

第四代单晶高温合金标准热处理试样和铸态试样压痕后分别在1100,1150,1200,1250,1300℃和1340℃退火处理,采用光学显微镜、扫描电镜、电子背散射仪研究不同条件的再结晶组织。结果表明:1100,1150,1200℃退火处理后,标准热处理试样和铸态试样都出现胞状再结晶。1250℃退火处理后,标准热处理试样和铸态试样都为混合再结晶。1300℃退火处理后,标准热处理试样再结晶组织全部为等轴再结晶,而铸态试样仍为混合再结晶。1340℃退火处理后,标准热处理试样和铸态试样都形成了等轴再结晶。随着退火温度升高,标准热处理试样和铸态试样的再结晶层深度明显增加,标准热处理试样再结晶深度明显大于铸态试样,相同条件下标准热处理试样的再结晶晶粒更容易长大。再结晶与基体的界面为小角度晶界、大角度晶界,而再结晶晶粒之间为小角度晶界、大角度晶界和孪晶界。孪晶在单晶高温合金再结晶的过程中发挥了重要作用。

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

The specimens of the fourth generation single crystal superalloy after heat treatment and at as-cast state were indented and annealed in vacuum at1100,1150,1200,1250,1300℃ and1340℃, 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 at1100,1150℃ and1200℃. Mixed recrystallization occurs in standard heat treatment samples and as-cast samples after annealing treatment at1250℃. Equiaxed recrystallization (ERX) develops when the standard heat treatment samples are annealed treatment at1300℃, while mixed recrystallization occurs in as-cast samples at same condition. ERX develops when these two samples are annealed at1340℃. 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.