Structural instability of plate-shaped θ' precipitates in an aged Al-Cu alloy

The present work verifies the structural instability of theta' precipitates, a primary strengthening phase in aged Al-Cu alloys, using atomic-scale imaging. A periodic structure of the precipitate has been found around the semi-coherent interface. In addition, the experimental results also show that the structure of the shear-resistant precipitate can be modified by long-time electron beam irradiation in the transmission electron microscope. During the process, stacking faults will be introduced in both the precipitates and the matrix, and a step with a height of four atomic layers will be formed on the coherent interface between precipitates and matrix.