Observing the dynamic rotation and annihilation process of an isolated nanograin at the atomic scale in Al

The atomic-scale dynamic evolution process of an isolated nanograin embedded within matrix under stress is recorded through in situ transmission electron microscopy tensile experiment on Al. the results reveal a 〈110〉 tilt grain boundary (GB) between the matrix and nanograin, with the misorientation angle increasing and GB shrinking during loading. A sudden annihilation of the nanograin occurs when the grain size reduces to ~4 nm. We then employ a dislocation dipole model to describe the GB structure in which the rotation, shrinkage and annihilation of nanograin can be interpreted as the approach and combination of opposite-sign dislocation pairs.