Research on the atomic-scale fracture mechanism of nickel-based superalloy DD6 at high temperature by a new in-situ technique in transmission electron microscopy

The fracture failure mechanism of high-temperature structural materials plays a vital role in the application of high-temperature structural materials. Transmission electron microscopy (TEM) is a unique tool providing the internal microstructures and defects of images in samples with up to atomic resolution. However, great challenges are posed to the realization of atomic-scale observation under thermal-mechanical coupling conditions in TEM. In this work, a thermomechanical testing apparatus combining micro-electro-mechanical system (MEMS) technology with a miniature piezoelectric ceramic inside TEM was developed, which enabled in-situ mechanical testing and high-resolution TEM analysis at elevated temperatures up to 873 K. This unique technique was used to investigate the atomic-scale fracture mechanism of nickel-based superalloy DD6 at high temperatures and stress for the first time. The fracture mode where cracks propagate along the γ and γ′ phase interfaces was proposed. Furthermore, the role of 60° full dislocations at the crack tip in crack propagation was revealed.