Microstructures and Mechanical Properties of Dual Phase Alloys Consisting of the Intermetallic Phases Ti3 (Al, Si) and Ti5(Si, Al)3

Abstract

ABSTRACTAlloying additions of silicon to the intermetallic titanium-aluminide Ti4Al lead to two-phase microstructures consisting of α2-Ti3(Al, Si) and Ti5(Si, Al)3.Although details of the ternary Ti-Al-Si phase diagram are not available, theoretical analysis and experimental screening have indicated the existence of a eutectic line in the Ti-rich region of the Ti3Al + Ti5Si3 two-phase region. The eutectic alloys display dual phase structures with Ti3(Al, Si) being the matrix and Ti5(Si, Al)3 the second phase.In this paper the microstructures of the eutectic as well as hypoeutectic and hyper-eutectic alloys, which contain additionally primary Ti3(Al, Si) and Ti5(Si, Al)3 needles, respectively, are described. The influence of the particular microstructure on various temperature-dependent mechanical properties such as strength, ductility, creep and fracture behaviour has been investigated. Alloys with hypo-eutectic microstructures show promising high temperature mechanical properties.