Temperature effects on solid state bonding joints of ultrafine-grained CNT/Al–Cu–Mg composites

Abstract

The joining of CNT/Al composites is a technology bottleneck in its engineering application. In this study, a bonding method of ultrafine-grained CNT/Al–4Cu–1Mg composites was performed. Microstructure and mechanical properties of the joints were characterized, then the interface bonding process and mechanism were explored. The results indicate that increasing temperature can accelerate the healing of interface voids and the dissolution of interface oxides, but overheat will lead to the softening of bonding joints and the conversion of CNTs to Al4C3. Under the optimal temperature of 500 °C, the bonding interface has basically healed, and the bonding strength is up to 380 MPa, which exceeds 90 % of the strength of raw materials. Besides, the key to interface healing is the fragmentation and dissolution of interface oxides which have been identified as MgAl2O4. The bonding behavior is a synergistic effect of dynamic recovery, interface migration, and atomic diffusion. Especially, CNTs and Al4C3 phases provide short-circuit diffusion channels and also inhibit the softening of the joints.