Coherent strain of Guinier-Preston II zone in an Al-Zn-Mg-Cu alloy

The Guinier-Preston (GP) II zone in an Al-Zn-Mg-Cu alloy was investigated by using a high-resolution electron microscopy (HREM). We used Geometric Phase Analysis (GPA) technique to measure the experimental HREM image and the simulated HREM image to obtain the strain distribution maps. The results show converging strain fields in the GP II zone, and the maximum compressive strain can reach - 7.2% and - 6.7%, respectively. The distribution of the experimental strain field was in consistence with that of the simulation result. The average strain of the alloy measured using XRD is 0.191%.