| Summary: | 碩士 === 國立臺灣大學 === 機械工程學研究所 === 93 === Dynamic wetting angles and microstructures of Ag-Cu-Ti-Zr active filler alloys on 99.5wt.% and 95wt.% Al2O3 substrates using infrared heating has been performed in the study. Experimental results show that Ag-Cu-6Ti-6Zr (wt.%) has better wettability than Ag-Cu-1.5Ti-1.5Zr (wt.%) due to Zr oxidation of the latter filler on Al2O3 substrate. The relationship between the wetting angle and time can be fitted well by the equation proposed by Ambrose et al. in which the characteristic time τis modified by τ×R, where R is a correction constant. Microstructural observations show that the interface between Ag-Cu-6Ti-6Zr and Al2O3 forms Ti3.3Cu2.7O layer. In contrast, the interface of Ag-Cu-1.5Ti-1.5Zr and Al2O3 forms ZrO2 layer. In this study, the joining of Ti-6Al-4V and 17-4 PH S.S. using the BAg-8 filler alloy is also performed. A diffusion barrier coated on the 17-4 PH S.S. is introduced prior to infrared brazing. The aim of introducing the diffusion barrier(s) is to prevent interdiffusion between two dissimilar alloys from forming intermetallics, so better bonding strength can be expected. Experimental results show that the best shear strength can be obtained from electroless-plating the Ni film on the 17-4PH S.S. Compared with the going of electroless-plating Ni film on 17-4PH S.S. and that of electroplating Cr film on 17-4PH S.S., the former has less Ti-Cu intermetallics and replaced by TiNiCu and NiPTi phases in the infrared brazed joint. Both joints do not have the interfacial TiFe compound and the fractures occur at the Ti-Cu intermetallics in between Ti-6Al-4V and filler for the joints brazed at 800℃ and 850℃.
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