Comments on a comparison of early and recent work on the effect of trace additions of Cd, In, or Sn on nucleation and growth of θ′ in Al-Cu alloys

The role of trace elements X (Cd, In or Sn) in theta' formation in Al-Cu alloys is considered. Two processes may occur: (i) heterogeneous nucleation on small particles of X (mainly at 200 degreesC and above) and (ii) incorporation of atoms of X into the theta' nuclei reducing the misfit with the aluminium matrix (principally at lower temperatures). (C) 2002 Acta Materialia Inc. Published by Elsevier Science Ltd. All rights reserved.