Abstract
Previously we reported on the changes of aspects of matrix precipitates in Cu-0.5, 1.0, 1.3, 2.0 and 4.0%Ti alloys. In this paper, we studied on precipitation due to grain boundary reaction with the same alloys. The results are summarized as follows:
(1) Cellular precipitates are observed in higher Ti content alloys, and grain-boundary precipitates attend with PFZ are observed in lower Ti content alloys at the same aging temperature.
(2) Width of PFZ observed in Cu-1%Ti alloys during aging at 450∼550°C, becomes narrower with aging time and then broader again with preferential growth of grain-boundary precipitates.
(3) Nucleation sites of the cellular precipitates are considered to be the grain boundary surface in 4%Ti alloys and grain boundary edge in 2%Ti alloys in the aging at 450°C by the thory of Cahn. Activation energy for growth of cellular precipitates is about 30 kcal/mol for both alloys.
