Motohiro Kanno1, Hisashi Suzuki1 and Osamu Kanoh2
1Department of Metallurgy and Materials Science, Faculty of Engineering, The University of Tokyo, Tokyo
The θ' precipitation was studied in an Al-4%Cu-0.060%In alloy aged at 473 K by transmission electron microscopy, EDXS analysis, etc., to clarify the phenomenon of aging acceleration widely known in this alloy. The aging structures of Al-4%Cu-0.065%Sn and Al-4%Cu-0.096%Cd alloys as well as Al-4%Cu alloy were also studied.
It was found that indium rich precipitates formed finely at an early stage of aging, resulting in the heterogeneous nucleation of θ' on those precipitates. The results were common in three sorts of ternary alloys. However, some differences in hardening rate and peak hardness were observed among the alloys, and these differences were attributed to the difference in size and distribution-density of In, Sn or Cd rich precipitates acting as a nucleation site for θ'.
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