| Summary: | 碩士 === 國立臺灣大學 === 材料科學與工程學研究所 === 90 === TiAl intermetallic joined by infrared vacuum brazing using Ag-based and Al-based filler metals is performed in this study. Experimental results show that pure silver as filler metal can obtain the best shear strength of 385MPa and BAg-8 is the next with the shear strength of 343MPa. For pure silver filler metal, TiAl brazed at 1100℃for 180 seconds has a new Ag17.7Al56Ti26.3 phase in the braze. For BAg-8 filler metal, the specimens are fractured at the residue filler metal when the brazing time is less than 120 seconds. Further increasing the brazing time, the fractured location changes from the residue filler metal into the interface of substrate/filler metal. At this time, AlCuTi phase forms abundantly at the interface and deteriorates the bonding property due to its high hardness. For BAlSi-4 filler metal, both of the transient AlSi3Ti2 phase and the stable Al12Si3Ti5 phase are observed at the interface of filler metal/substrate. Further increasing the brazing time, the TiAl2 phase is formed via solid-state interdiffusion between Al12Si3Ti5 and TiAl substrate. The maximum shear strength of joined specimen using BAlSi-4 filler metal is 76.4 MPa. For pure aluminum filler metal, only stable TiAl3 phase forms at the joint and results in the inherent brittleness.
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