Microstructure and hardness of as-cast Ti-45Al alloy with different fe contents

The button ingots of Ti-45Al-xFe alloy were obtained using a non-consumable electric arc melting furnace. The effect of Fe contents on the microstructure and hardness of the as-cast alloys was investigated by optical microscope(OM), scanning electron microscope(SEM) and Rockwell hardness tester. The results showed that the microstructural evolution of Ti-45Al-xFe alloys experienced the following stages in turn: dendrite morphology with quadruple symmetric→dendrite morphology with quadruple symmetric, smaller interdendritic γ phases and a small amount of B2 phases→dendrites morphology with a six fold symmetric, lath shaped gamma phases and a mass of B2 phases. The precipitation of B2 phase increased in Ti-45Al-xFe alloy. In addition, with the increase of Fe content, the primary phase transformed from β phase to α phase during the solidification process of Ti-45Al-xFe alloys. As displayed by the hardness analysis, the hardness fitting curve of Ti-45Al-xFe alloys firstly decreased and then increased, which was mainly due to that large amounts of B2 phases precipitated and the microstructure changed. When Fe content was 5% (atom fraction), the morphology of B2 phase had a remarkable change. It transformed to honeycomb morphology, which induced an increase in the hardness of Ti-45Al-xFe alloy.