Identifying the microstructural features associated with void nucleation during elevated-temperature deformation of copper

The microstructural-scale mechanisms that produce cracks in metals during deformation at elevated temperatures are relevant to applications that involve thermal exposure. Prior studies of cavitation during high-temperature deformation, for example, creep, suffered from an inability to directly observe the microstructural evolution that occurs during deformation and leads to void nucleation. The current study takes advantage of modern high-speed electron backscatter diffraction (EBSD) detectors to observe cavitation in oxygen-free, high-conductivity copper in situ during deformation at 300 degrees C. Most voids formed at the triple junction between a twin boundary and a high-angle grain boundary (HAGB). This finding does not contradict previous studies that suggested that twins are resistant to cracking-it reveals that cracks in HAGBs originate at twin/HAGB triple junctions and that cracks preferentially grow along HAGBs rather than the accompanying twins. Atomistic simulations explored the origins of this observation and suggest that twin/HAGB triple junctions are microstructural weak points.

Automated summary

This study utilizes modern high-speed electron backscatter diffraction technology to observe cavitation in oxygen-free, high-conductivity copper during deformation at elevated temperatures. The results show that voids mainly form at the triple junction between a twin boundary and a high-angle grain boundary. This study reveals that cracks originate at twin/high-angle grain boundary triple junctions and preferentially grow along high-angle grain boundaries.