Phase equilibria in the Ti-Al-W system between 800 and 1300 °C

Abstract

Within the search for new improved high-temperature materials for gas turbine applications with higher energy saving potential and improved greenhouse gas balance, new Ti-Al-W based alloys have recently been discussed. A basic prerequisite for targeted alloy development is the precise knowledge of the phases and phase relationships that determine the microstructure and mechanical behavior of the material. However, there is not much known about the phase equilibria in the application- and manufacturing-relevant temperature range between 800 and 1300 °C. No information on ternary intermetallic compounds or possible ordering of the cubic (βTi,W) solid solution is reported in the literature. In the present investigation, the Ti-rich part of the Ti–Al–W system between 800 and 1300 °C was studied. Ten different alloys were heat-treated and quenched samples were characterized by scanning electron microscopy (SEM), electron probe microanalysis (EPMA), high-energy XRD (HEXRD), differential thermal analysis (DTA), and transmission electron microscopy (TEM). Based on these results, a series of partial isothermal sections was established. The investigations show that there is no ternary intermetallic compound in this system and the (W) solid solution forms equilibria with the binary Ti-Al phases.