Anisotropy in Strength of a TiAl Base Polycrystal with Unidirectionally Oriented Lamellae

Abstract

A Ti-44.1 at%Al-1.6 at%Mn alloy with a unidirectionally oriented lamellar structure was made by using heavy extrusion of a mixture of titanium and Al-Mn alloy powder followed by reactive sintering under HIP. Compression tests were performed for 5 × 5 × 6 mm 3 specimens prepared in such a way that the angle between the extrusion direction and the compression axis became 0°, 30°, 45°, 60° or 90°. The yield strength at 293 K is found to strongly depend on the above angle, i.e., the 0° specimen shows the highest strength, the 90° specimen the second while the other specimens show much lower strengths. A similar anisotropic yield strength is observed for the results obtained at 1073 K although the strength of the 0° specimen is much higher than that in the 90° one. Anisotropic deformation behavior observed in the present investigation is discussed in comparison with that for TiAl polysynthetically twinned crystals.