CREEP-INDUCED PHASE-TRANSFORMATIONS IN FURNACE COOLED ZN-AL ALLOY

Phase transformation and microstructural change of a furnace-cooled eu tectoid Zn-Al alloy specimen (76 wt % Zn-22 wt % Al-2 wt % Cu) were in vestigated during creep testing by using scanning electron microscopy and X-ray diffraction techniques. Creep-induced decomposition of a met astable <eta(T)'phase and a four-phase transformation, alpha + epsilon --> T' + eta, occurred during the creep testing. Also microstructural change was observed from a lammellar structure partially into a spher oidized structure in the rupture part of the furnace-cooled alloy. The mechanism of the creep rupture of the furnace-cooled eutectoid Zn-Al alloy was also discussed.