Infrared brazing Cu and Ti using a 95Ag-5Al braze alloy
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RODUCTION
THE joining of pure titanium and copper currently is applied for the production of titanium targets used in physical vapor deposition (PVD) infrastructures. In this process, it is desirable that the high-purity titanium target is bonded with the water-cooled oxygen-free copper substrate without significant loss of its thermal conductivity. Brazing is often one of the best choices in manufacturing of the Ti target due to the high thermal conductivity of the brazed joint as compared with adhesive bonding.[1,2] It has been reported that the titanium alloy can be successfully brazed with several silver-based braze alloys,[2–6] and 95Ag-5Al in weight percent is a type of silver-based braze alloy. The melting point of pure Ag is significantly decreased with 5 wt pct Al additions, resulting in solidus and liquidus temperatures of 95Ag-5Al braze being 780 °C and 810 °C, respectively.[2] Infrared heating is a novel technique characterized by an extraordinary fast heating rate up to 3000 °C/min.[7] Thus, the interfacial reaction among the molten braze and substrates during infrared brazing may be greatly decreased due to the rapid thermal history. Accordingly, there are many successfully infrared-brazed joints demonstrated in previous studies.[7–10] This research investigates infrared brazing Cu and Ti using the 95Ag-5Al braze alloy. Dynamic wetting angle measurement, microstructural evolution, reaction kinetics across the brazed joint, and shear strength are comprehensively evaluated in the experiment. II. MATERIAL AND EXPERIMENTAL PROCEDURES The base metals used in the experiment were commercially pure titanium plate and oxygen-free copper plate. 95Ag-
R.K. SHIUE, Associate Professor and S.K. WU, Professor, are with the Department of Materials Science and Engineering, National Taiwan University, Taipei 106, Taiwan. C.H. CHAN, former Graduate Student, is with the Department of Mechanical Engineering, National Taiwan University, Taipei 106, Taiwan. Contact e-mail: [email protected] Manuscript submitted December 12, 2003. METALLURGICAL AND MATERIALS TRANSACTIONS A
5Al alloy was chosen as the brazing filler metal, and braze alloy foil with thickness of 100 m was used throughout the experiment. Figure 1(a) illustrates the schematic diagram of the wetting angle measurement device. The instrument was composed of three major parts, an infrared vacuum furnace, a specimen holder, and the image analysis system. The ULVAC* *ULVAC is a trademark of ULVAC Japan, Ltd., Japan.
SINKO-RIKO RHL-P816C infrared furnace was used as the main body of the vacuum furnace. The measurement was performed in a vacuum of 5 105 mbar throughout the experiment. Infrared rays were generated from the infrared lamps, transmitting through a transparent quartz tube and focused on the specimen holder. One end of the quartz tube was attached to the specimen holder, and the other end could transmit the signal into the image analysis system. An enlarged diagram of the specimen holder is shown in Figure 1(b). The filler metal was located on the sub
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