Characterization of Vacuum Brazing of Ti6Al4V and Alumina With Cu-Ag Brazing Alloy via Substrate-Induced Reactive Mechanism

Abstract

Brazing of ceramic and metal components is an emerging manufacturing technology in which a furnace or a heat source is used to join the substrates using a brazing filler material. Brazing of ceramic and metal has received considerable attention in the field of nuclear reactor, aerospace, automobile, medical and electrical engineering. A brazing alloy can either be a conventional brazing alloy which requires the ceramic surface to be metallized or an active brazing alloy which does not require metallization. A sound interfacial adhesive bond is formed during the process. The typical active elements required in the brazing alloy for bonding of alumina are Ti and Zr. It is expected that since Ti is present in Ti6Al4V, a copper-silver alloy (Cusil™) without an active element can be used for brazing. The Ti substrate itself could provide the reactive element because of dissolution. Vacuum brazing of alumina and titanium with Cusil sheet has been carried out to analyze the characteristics of the joint. Behavior of the joint under different temperature conditions has been studied by thermal cycling of the joint. Uniformity of the joints is confirmed by observing the Scanning electron microscope (SEM) images. The elements and phases present in the joint interface are observed by energy dispersive spectroscopy (EDX) and X-ray diffraction (XRD) analyses. The maximum shear strength obtained in the brazedTi6Al4V/Cusil sheet/alumina joint was 102MPa and the average shear stress was found to be 70±3 MPa. The micro-Vickers hardness test showed that the micro hardness of the interface was lower than the substrates.