Effects of Electromagnetic Fields on Interfacial Bonding Strength of Ti/Al Clad Sheet Processed by Horizontal Twin-Roll Casting

In this study, a Ti/Al clad sheet was fabricated using horizontal twin-roll casting (HTRC) with the application of pulsed electric field (PEF) and electromagnetic oscillation field (EOF), and the effects of different external fields on interfacial bonding strength were investigated in detail. The external electromagnetic fields have little influence on the stability of HTRC process. With the application of PEF and EOF, the width of diffusion layer at the Ti/Al interface increases obviously, and the interfacial bonding strength increases from 20.1 to 21.4 N/mm and 24.5 N/mm, respectively. When the EOF is applied, the electromagnetic volumetric force is generated in the liquid cavity of cast-rolling zone, which is much larger than the electromagnetic force caused by single PEF. Under the action of the electromagnetic volume force, aluminum melt in the liquid cavity oscillates repeatedly, which scours the surface of the titanium strip and makes the newly formed crystal nuclei fall off the surface of strip. In addition, the oscillation effect reduces the temperature gradient at the contact area between strip and melt and slows down the solidification process, thus prolonging the contact time between aluminum and titanium. All of these effects make the melt spread more sufficient on the surface of titanium strip and promote the interdiffusion between atoms. As a result, more metallurgical bonding regions are formed and enhanced, which leads to the improvement of bonding strength of the clad sheet.