Korean Journal of Materials Research ISSN:1225-0562(Print) 2287-7258(Online) 한국재료학회지

The microstructural evolution and modulation of mechanical properties were investigated for a Ti₆₅Fe₃₅ hypereutectic alloy by addition of Bi₅₃In₄₇ eutectic alloys. The microstructure of these alloys changed with the additional Bi-In elements from a typical dendrite-eutectic composite to a bimodal eutectic structure with primary dendrite phases. In particular, the primary dendrite phase changed from a TiFe intermetallic compound into a β-Ti solid solution despite their higher Fe content. Compressive tests at room temperature demonstrated that the yield strength slightly decreased but the plasticity evidently increased with an increasing Bi-In content, which led to the formation of a bimodal eutectic structure (β-Ti/TiFe + β-Ti/BiIn containing phase). Furthermore, the (Ti₆₅Fe₃₅)₉₅(Bi₅₃In₄₇)₅ alloy exhibited optimized mechanical properties with high strength (1319MPa) and reasonable plasticity (14.2%). The results of this study indicate that the transition of the eutectic structure, the type of primary phases and the supersaturation in the β-Ti phase are crucial factors for controlling the mechanical properties of the ultrafine dendrite-eutectic composites.