Unstable stacking faults in submicron/micron Al grammins in multi-SiCp/multi-Al nanocomposite

•Stacking faults in submicron/micron Al grains was observed in nanocomposite.•Zigzag defects and linear defects were observed in submicron/micron Al grains.•The stacking faults contain Frank partial dislocations and twinning.•The defects would “disappear” under electron beam irradiation in a few seconds.

It is difficult to obtain planar defects in aluminum due to its high stacking fault energy, in particular in submicron/micron Al grains. In this work we provide evidence for planar defects in submicron/micron Al grain of composites with multi nano-particles by transmission electron microscope observations. Nano-SiC particles (<100 nm) were found within micron-Al grains (>2 μm), while submicron SiC particles (200–500 nm) were present at the boundary of ultrafine Al grains (100–500 nm). Zigzag defects and linear defects were observed in both the micron-Al grains and ultrafine Al grains. These defects are made up of distortion areas, edge dislocations, stacking faults which contain Frank partial dislocations and twinning. Therefore, these defects are in a state of extreme instability, which would “disappear” under the electron beam irradiation in a few seconds. These results highlight that the increase of interface could lead to the formation of stacking faults, even in the micron Al grains.