Vacuum brazing TiAl-based intermetallics using novel Ti–Fe–Mn eutectic brazing alloy

Abstract

Ti–22Fe–23Mn(at.%) eutectic brazing alloy ribbon fabricated by vacuum arc remelting and rapid solidification as filler metal used to vacuum braze Ti–45Al–2Mn–2Nb–1B(at.%) alloy. The effects of brazing temperature and time on the interfacial microstructure and joining properties were investigated in detail. The microstructure of the Ti–20Fe–21Mn brazing alloy presented excellent diffusion ability, and the brazed joints mainly consisted of α2/γ lamellar phase, single α2 phase, B2 phase, and boride. The brazed joint's tensile strength first increased and then decreased with the brazing temperature in the range of 1170 °C–1250 °C, and the holding time varied from 5 min to 60 min. The highest tensile strength at room temperature was 540 MPa when the joint brazed at 1230 °C for 45 min. The high-temperature tensile strength first increased and then decreased with the testing temperature. The high-temperature tensile strength of Ti–22Fe–23Mn(at.%) alloy was superior to Ti–Zr–Cu–Ni (at.%) alloy. The high-temperature tensile strength was lower than 45XD alloy below 850 °C. However, the tensile strength was closer to 45XD alloy when the testing temperature varied from 900 °C to 1000 °C. All the cracks nucleated and propagated in the poor boride zone, and the fracture surfaces presented typical brittle cleavage fracture characteristics.