Effect of Bonding Temperature on Microstructure Development during Transient Liquid Phase Bonding of Ti_2AINb Alloy Using Ti-Zr-Cu Based Filler Alloy

摘要

Transient liquid phase (TLP) bonding of Ti_2AlNb, used for vacuum brazing furnace, was carried out using Ti-Cu-Zr based foil as filler alloy at 950, 1000 and 1050°C. The effect of bonding temperature on joint interface, phase constitutions and their distributions were investigated by taking advantages of OM, SEM, EDS and XRD analyses. The result revealed that the TLP joint consisted of isothermally solidified zone and diffusion affected zone. A non-isothermally solidified zone existed only when the bonding temperature was not high enough. The interface morphologies of the joints were found to be very sensitive to the bonding temperature. With the bonding temperature increased from 950 °C to 1000°C, the width of non-isothermally solidified zone decreased from 69 urn to 23 um. When the bonding temperature was 1050°C, the non-isothermally solidified zone disappeared. Meanwhile, more alloying elements of Cu and Zr diffused most adequately into the base material. Phase analysis showed that along with the increasing of bonding temperature, the secondary phase constitution of joint changed from Ti(Cu,Al)_2 + AlNb_2 + Ti solid solution to Ti solid solution + Nb(CuAl) + Al_4Cu_9 + Al_2Zr_3, and the proportion of secondary phase was 35.7%, 20.2%, 6.7%, respectively. The morphology of base metal changed because of the relatively high bonding temperature was higher than 980 °C, the α→β transition temperature.