Abstract
Metastable phases in aluminium alloys are the primary nano-scale precipitates which have the biggest contribution to the increase in the tangible mechanical properties. The continuous increase in hardness in the 7xxx aluminium alloys is associated with the phase transformation from clusters or GP-zones to the metastable η′ phase. The high-resolution electron imaging is used to observe the precipitates and reconstruct a kinetic model that might explain the transformation. This work is an attempt to gain insight into how the structural transformation may occur based on the shortest route of diffusion for the eventual structure to result in that of the η′ phase.