Ultrasonic-assisted brazing of SiC ceramic to Ti–6Al–4V alloy using a novel AlSnSiZnMg filler metal

• A novel Al–15.5Sn–9.5Si–4.5Zn–0.5Mg (wt%) filler metal was developed.
• The novel filler metals had a low solidus temperature of ~183 °C.
• SiC and Ti–6Al–4V were bonded well with the novel filler metal by ultrasonic.
• Integrity joints were obtained by using the novel filler metals.
• Thermal residual stress in the joint was at a low level.

Newly developed AlSnSiZnMg alloys were used as filler metals for ultrasonic-assisted brazing of SiC ceramics to Ti–6Al–4V alloys in air. The novel filler metal consisted of Al, Sn, Si, Zn, Mg2Sn, and Al2Mg phases. Compared with a typical AlSi eutectic filler metal, it had a low solidus temperature of ~183 °C, low elastic modulus (E-Modulus) and low coefficient of thermal expansion (CTE). The microstructure, thermal residual stress and mechanical properties of the joints were investigated. The intermetallic compound Ti7Al5Si12 formed at the Ti–6Al–4V side interface and a straight bonding interface existed at the SiC ceramic side. An integrated joint was obtained when using the novel filler metals, compared with the inner fractured joint obtained by filling with the common AlSi alloy. Thermal residual stress (TRS) in the joint filled with the novel alloy was at a safe level, which was mainly determined by the low solidus temperature of the novel filler metals and the nearly continuous Sn-rich phase in the resulting joint alloy. The average shear strength of the joints was ~77.8 MPa.