Microstructure and properties of the TiAl/GH3030 dissimilar joints vacuum-brazed with a Ti-based amorphous filler metal

Abstract

TiAl intermetallic was vacuum brazed to GH3030 alloy with a Ti-based amorphous filler metal (Ti33.3Zr16.7Cu39Ni11, at.%). The effect of the brazing temperature on the microstructural evolution and mechanical properties of the brazed joints was investigated. Ti3Al and Al(Cu, Ni)2Ti phases composed the diffusion zone I at the TiAl side resulting from the diffusion of Cu and Ni into TiAl intermetallic, and the diffusion zone III at GH3030 side consisted of α-Ni and α-Cr solid-solution phases and a TiNi3 intermetallic phase, which rooted in the diffusion of Ti into GH3030 alloy. Increasing the brazing temperature accelerated the diffusion and migration of the constituents, and further thickened all reaction zones. The growth rate of zones I and III was wzoneI = 0.0789 μm/oC and wzoneIII = 0.0833 μm/oC, respectively. The formation of zone III was more difficult than that of zone I with the growth activation energy (Q) of QzoneI = 101.96 kJ·mol−1 and QzoneIII = 165.58 kJ mol−1. The maximum shear strength was 260 MPa obtained at 960 °C/10 min. All brazed joints fractured at the interface of Al3(Cu, Ni)Ti2/Al(Cu, Ni)2Ti, because of the mismatch of their lattice structure and hardness, and all failed joints demonstrated zonal and brittle features.