紅外線硬銲接合Ti-6Al-4V與異質合金之研究

Abstract

This research is focused in infrared vacuum brazing Ti-6Al-4V (Ti-64) and other alloys. For the brazed Ti-64 and Ti50Ni50 joint using the Ag-Cu-1.75Ti filler, CuNiTi and Ti3Cu4 are formed adjacent to the Ti50Ni50 substrate, and AlCu2Ti is observed with increasing the brazing time and/or temperature. Ti2Cu, TiCu, Ti3Cu4 and TiCu4 are found nearby the Ti-64 substrate. The microstructural evolution of the joint using the Ag-Cu- 4.5Ti filler is similar to that of Ag-Cu-1.75Ti filler except for thicker Ti-Cu intermetallics. For the brazed Ti-64 and 17-4PH stainless steel (17-4 PH SS) with Cr/Ni coatings joint using the BAg-8 filler, the microstructure of Ti-64 side is similar to the aforementioned result. For the 17-4PH SS side, the Ni film is disappeared and dissolved into the braze resulting in the CuNiTi phase. It is found that introducing a thin layer of Ni film greatly improves the wettibility of the molten braze on the 17-4PH SS, so shear strengths of joints are more stable. For the use of Ag-Cu-1.75Ti filler to braze 17-4PH SS coated with Cr film, TiCr2 is formed next to the 17-4PH SS, and it impairs shear strength of the brazed joint. For the use of 60Ti-15Cu-25Ni filler to braze Ti50Al50 alloy, two layers are formed: one layer composed of α2-Ti3Al and γ-TiAl mixtures and the other having a continuous α2-Ti3Al phase. The residual filler in the brazed zone is composed of Ti2Cu and Ti2Ni. For 70Ti-15Cu-15Ni filler, the microstructural evolution of the joint is very similar to that of 60Ti-15Cu- 25Ni filler except for the decreased residual filler zone. The phase evolution of the joint brazed by 40Ti-20Zr-20Cu- 20Ni filler is changed because of introducing Zr, and there are at least three different phases formed in the residual filler zone.