Experimental examination of strain field within GP zone in an Al–Zn–Mg–Cu alloy

The strain field of GP zone plays a very important role in strengthening of the precipitation-hardened aluminum alloys by prohibiting movement of dislocations; however, quantitative analysis about the strain field of the GP zone in the aluminum alloys has been seldom reported elsewhere. In this paper, the microstructure of GP zone in an Al–Zn–Mg–Cu alloy was explored by using high-resolution transmission electron microscopy (HRTEM), and the displacement field of lattice planes within the GP zone was experimentally measured by geometric phase analysis (GPA) technique; then, the quantitative results about strains of the distorted lattice planes within the GP zone were also obtained. It is found that the GP zone core is convergence region of the strains, and the maximum value of the compressive strains within the GP zone is about 7.6%.