Influence of equal-channel angular pressing on precipitation in an Al–Zn–Mg–Cu alloy

Processing by equal-channel angular pressing (ECAP) affects the morphology of η precipitates in an Al–Zn–Mg–Cu (Al-7136) alloy. It is shown by transmission electron microscopy that ECAP changes the orientation of precipitates and this influences the atomic configuration and the interfacial energy at the η/α-Al interfaces. Consequently, η precipitates adopt an isotropic growth mode and evolve into equiaxed particles. A three-dimensional atom probe analysis demonstrates that large η precipitates formed in different numbers of ECAP passes are of similar composition. The coalescence of smaller precipitates, rather than the fragmentation of larger precipitates, dominates the precipitate evolution.