Influence of the particle size on recrystallization and grain growth in Al-Mg-X alloys

Recrystallization and grain growth studies of Al-Mg-X (where X is Mn, Zr or Sc) alloys have been carried out using a combination of optical and transmission electron microscopy of interrupted heating tests, changes in hardness, and in-situ observations in the transmission electron microscope. Nucleation sites have been identified as typically large (> 1 μm diameter) eutectic constituent particles, but also occasionally clusters of sub-micron dispersoids. By altering the density and size of the Mn-, Sc- and Zr-based particles with selected thermomechanical treatments, recrystallization could be suppressed up to temperatures near the melting point. These results can be explained by examination of the stored energy from cold work and the particle-substructure interactions due to the precipitate morphology. Implications of these results for grain size control in Al-Mg based alloys will be discussed.