Microstructure Evolution of GH4742 Ni-Based Superalloy during Hot Forming

In this work, the microstructure evolution and dynamic recrystallization (DRX) mechanism of double-cone specimens of GH4742 superalloys during hot compression were studied by means of various microtechniques. Two hot deformation regimes are designed and implemented, i.e., gamma single-phase region (1080-1100 degrees C) and gamma + gamma ' double-phase region (1120-1140 degrees C). Microstructure analysis shows that coarse carbides (> 1 mu m) promote the development of DRX through PSN, and the contribution to recrystallization is more than 5 times that of the fraction of carbides. Moreover, the average recrystallized grain size of PSN is always smaller than the average DRX grain size, and it does not exceed 7 mu m and even deforms at a higher temperature of 1140 degrees C. When deformed in the double-phase region, a large number of fine gamma' particles with a diameter less than 0.8 mu m hinder DRX. In addition to traditional dynamic recrystallization (DRX), twin recrystallization begins at the initial deformation twin boundary, and necklace recrystallized grains are formed inside the grains.

Automated summary

This study investigated the microstructure evolution and dynamic recrystallization mechanism of GH4742 superalloys double-cone specimens during hot compression using various microtechniques. It was found that carbides and γ' phase particles have different effects on the DRX process.