MECHANICAL ALLOYING OF ZN-RICH ZN-AL-CU ALLOYS

Zn-rich Zn-Al-Cu alloys were produced by milling of elemental powders mixtures, Zn-22 wt.% Al-3 wt.% Cu and Zn-20 wt.% Al-10 wt.% Cu, for ti mes of up to 1080 ks. The X-ray diffraction analysis showed the format ion of alpha (aluminum-rich), eta (zinc-rich) and epsilon (CuZn4) phas es at the early stage of milling. The presence of epsilon phase was mo n evident with the increase of copper content in mixture. In the case of the two alloy compositions. the following phase transformation alph a + epsilon --> eta + tau' was observed to occur during milling. A mix ture of eta, alpha and tau' phases was found in powder mixtures milled for 1080 ks, which is in agreement with phases predicted for these co mpositions in the equilibrium Al-Cu-Zn phase diagram. Finally, all the se phases were present on a nanometer scale in both mechanically alloy ed powders.