Infrared brazing of Ti-6Al-4V using the Ti-15Cu-15Ni braze alloy

Abstract

Titanium and its alloys are relatively new engineering metals because they have been used as structural materials only since 1952 [1]. Ti-6Al-4V is by far the most important and widely used titanium alloy, accounting for 60% of the titanium market in 1989. It can be readily welded, forged and machined [1]. However, the welding of Ti alloys may be not appropriate for all applications such as titanium honeycomb sandwich structure [2]. In such a case, brazing is a better way to join the titanium alloy. However, selection of filler metals used in brazing titanium alloys is critical to avoid the formation of undesirable intermetallics [2]. Ti-15Cu-15Ni in weight percent is a successful commercially available brazing filler metal which can braze titanium and its alloys [2–4]. Ti-15Cu15Ni can be used at temperatures up to 870 ◦C, and it is used in this study. Infrared brazing is featured with a very high heating rate of up to 3000◦C/min, and many successful joints have been made by infrared brazing [5–10]. Accordingly, it is a novel technique applied in brazing many structural alloys. The purpose of this research is focused on vacuum brazing including traditional furnace brazing and infrared brazing Ti-6Al-4V alloy using the Ti-15Cu-15Ni filler metal. The wetting angle measurement, microstructural evolution, and shear strength of the brazed joint are extensively assessed in the experiment. Ti-6Al-4V plate with the dimension of 10 × 10 × 3 mm was used in the experiment. The substrate was polished by SiC papers up to 1200 grits, and subsequently cleaned using an ultrasonic bath with acetone as the solvent prior to brazing. Ticuni R © foil purchased from Wesgo, Inc. was used as the brazing filler metal. Its nominal composition is 15%Cu, 15%Ni and Ti balance. The dimensions of Ticuni R © foil are 100 mm width and 50 μm thickness. The solidus and liquidus temperatures of the Ticuni R © foil are 910 and 960◦C, respectively.