Experimental investigation and thermodynamic optimization of the Al-Zn-Ti system in the Al-rich corner

The phase relationships of the Al-Zn-Ti system in the Al-rich corner (up to 25 at.% Ti and 60 at.% Zn) at 500 degrees C and 400 degrees C were experimentally studied. The annealed samples were investigated by means of optical microscopy (OM), scanning electron microscopy (SEM), energy dispersive X-ray spectrometer (EDS) and X-ray powder diffraction (XRD). The experimental results showed that the ternary phase tau -Ti25Al75-xZnx (x = 19-60) was stable in the temperature range of 400-500 degrees C. A new Ti28Al68Zn4 phase different from TiAl3 phase was in equilibrium with (Al) and tau in the Al-rich corner. Based on the isothermal experimental data at 500 degrees C and 400 degrees C, a set of self-consistent thermodynamic description of the Al Zn Ti system was obtained. (C) 2012 Elsevier Ltd. All rights reserved.