The effect of processing and porosity on the elastic moduli of gamma-TiAl

The effect of porosity on the dynamic elastic moduli of γ-TiAl samples that had been consolidated by cold isostatic pressing (CIP), pressureless sintering and hot isostatic pressing (HIP) was studied by ultrasonic sound velocity measurements. The results indicate that the sound wave velocities and the elastic moduli are affected by the processing route and depend not only on the density that was attained but also on the temperature at which the consolidation was performed. The effect of pressure on both the density and elastic moduli of samples that had undergone CIP or low temperature HIP (T∼700°C) is limited. Pressureless sintering in the 700 to 1100°C temperature range barely affects the density but substantially the elastic moduli. In the 1150 to 1420°C temperature range, both density and elastic moduli increase. High temperature HIP (T∼1150°C) yields nearly fully dense compacts with Young's modulus of 197 GPa and Poisson's ratio of 0.22. The elastic moduli follow a linear dependence on porosity in the 0 to 0.4 range. The nature of the interparticle interface is an important factor in determining the elastic moduli of the consolidated product.