Isothermal decomposition of some beta Cu-Zn-Al alloys with e/a=1.48

The isothermal aging effects in some beta Cu-Zn-Al alloys containing betwee n 9.98 and 16.33 at.% Al and a constant electron per atom ratio, e/a, of 1. 48, were studied by optical and electron microscopy and time dependence of microhardness and electrical resistivity in the temperature range of 473 an d 773 K. On aging, for all compositions, the beta phase decomposes into a m ixture of (alpha + gamma) phases, with an earlier formation of gamma phase in alloys with higher Al content. The hardness and the electrical resistivi ty increase with aging time at each temperature, but the causes of these ch anges are not the same: the hardness variations are associated mainly with the gamma precipitation while the resistivity changes are related to the eu tectoid decomposition. (C) 1999 Published by Elsevier Science S.A. All righ ts reserved.