Effect of thermomechanical processing on evolution of superplastic microstructures in Al-Cu-Zr alloys

The role of alloying elements and the effect of prior cold work on microstr uctural evolution in Supral type alloys during high temperature straining h as been investigated by examining a range of binary and ternary alloys cont aining varying amounts of Cu and/or Zr, After hot compression, specimens we re rapidly cooled to retain the evolved structure and then examined using a range of techniques including optical microscopy, electron microscopy (sca nning and transmission), and boundary misorientation measurements from elec tron backscattering patterns. The high temperature evolution of a fine grai n, high angle boundary structure, without nucleation, and growth, was seen to be strain induced and required prior work and the presence of both Cu an d Zr, Of the various mechanisms which have been proposed for the continuous recrystallisation of Supral type alloys, the present work is consistent wi th the importance of strain induced geometrical dynamic recrystallisation i n microstructural evolution, and has identified the role of the alloying ad ditions and the processing variables. MST/4382.