Solid-liquid cast-rolling bonding (SLCRB) and annealing of Ti/Al cladding strip

Abstract

By feeding the solid titanium strip together with the molten aluminum into the twin-roll caster simultaneously, Ti/Al cladding strips were successfully fabricated in a solid-liquid cast-rolling bonding (SLCRB) process. Annealing treatment was subsequently applied on the Ti/Al cladding strips to eliminate the residual stress and improve the bonding quality. The microstructure, composition of the interface reaction products and bonding strength were investigated by scanning electron microscope (SEM), energy dispersive spectrometer (EDS), peeling and tension-shear test. It indicates that, at the beginning of the cast-rolling process, diffusion reaction occurs at the interface of the liquid aluminum and the titanium strip. At the exit of caster, the bonding interface presents jagged bite due to the hot rolling, and the thickness of diffusion layer is about 3μm. After annealing treatment at 520°C for more than 2h, a continuous compound layer was generated on the bonding interface and the composition is single TiAl3 phase. The influence of annealing time on the thickness of diffusion layer was discussed and it indicates that the interface growth kinetics obeys linear law from 25h to 200h. Annealing treatment can improve the adhesive strength of the cladding strip. After annealing treatment for 25h, the average peeling strength increases from 21N/mm to 27N/mm. The micro-morphology of the peeled surface was subsequently investigated, and the SEM images show that the Ti side surface is almost completely covered with aluminum, which indicates that the fracture is located at aluminum substrate.