Lamellar Microstructure Alignment in Ti-47Al Alloy by Electromagnetic Confinement and Directional Solidification Using a Seed

As a promising electromagnetic process to obtain TiAl samples without contamination, electromagnetic confinement and directional solidification was successfully applied for lamellar microstructure control in Ti-47Al alloy. Seeded by a Ti-43Al-3Si seed, columnar α grains grew stably and the lamellae within these grains were aligned parallel to the growth direction. However, stray α or β grains, in which the lamellae were complex, nucleated and grew in the sample edge. The possible reasons for the formation of stray grains were discussed by analyzing the temperature gradient at the solid/liquid interface and the macrosegregation of Ti5Si3 particles and Al solute along the sample radius. Moreover, the fluid flow induced by electromagnetic force, which led to the macrosegregation, was also discussed by using a simple model.