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, cha nges in hardness, and in-situ observations in the transmission electro n microscope. Nucleation sites have been identified as typically large (> 1 mu m diameter) eutectic constituent particles, but also occasion ally clusters of sub-micron dispersoids. By altering the density and s ize of the Mn-, Sc- and Zr-based particles with selected thermomechani cal treatments, recrystallization could be suppressed up to temperatur es near the melting point. These results can be explained by examinati on of the stored energy from cold work and the particle-substructure i nteractions due to the precipitate morphology. Implications of these r esults for grain size control in Al-Mg based alloys will be discussed. (C) 1997 Elsevier Science S.A.