Isothermal decomposition of some β Cu–Zn–Al alloys with e/a=1.48

The isothermal aging effects in some β Cu–Zn–Al alloys containing between 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 and 773 K. On aging, for all compositions, the β phase decomposes into a mixture of (α+γ) phases, with an earlier formation of γ phase in alloys with higher Al content. The hardness and the electrical resistivity increase with aging time at each temperature, but the causes of these changes are not the same: the hardness variations are associated mainly with the γ precipitation while the resistivity changes are related to the eutectoid decomposition.