Novel twin-roll-cast Ti/Al clad sheets with excellent tensile properties

Abstract

Pure Ti or Ti alloys are recently spot-lighted in construction industries because they have excellent resistance to corrosions, chemicals, and climates as well as various coloring characteristics, but their wide applications are postponed by their expensiveness and poor formability. We present a new fabrication process of Ti/Al clad sheets by bonding a thin Ti sheet on to a 5052 Al alloy melt during vertical-twin-roll casting. This process has merits of reduced production costs as well as improved tensile properties. In the as-twin-roll-cast clad sheet, the homogeneously cast microstructure existed in the Al alloy substrate side, while the Ti/Al interface did not contain any reaction products, pores, cracks, or lateral delamination, which indicated the successful twin-roll casting. When this sheet was annealed at 350 °C~600 °C, the metallurgical bonding was expanded by interfacial diffusion, thereby leading to improvement in tensile properties over those calculated by a rule of mixtures. The ductility was also improved over that of 5052-O Al alloy (25%) or pure Ti (25%) by synergic effect of homogeneous deformation due to excellent Ti/Al bonding. This work provides new applications of Ti/Al clad sheets to lightweight-alloy clad sheets requiring excellent formability and corrosion resistance as well as alloy cost saving.

Effect of Post-Heat Treatment Temperature on Interfacial Mechanical Properties of Cold-Rolled Ti/Al Clad Material

“…In addition, no phase transformations of Ti and Al occur at the post-heat treatment temperatures. In general, the intermetallic compound layer at the interface of dissimilarly jointed materials can improve the interfacial strength, but reduce the interfacial properties, owing to its brittleness [ 39 , 40 ]. Therefore, there is a critical thickness of the intermetallic compound layer, which is sufficient to ensure proper bonding properties while being not too large to degrade the mechanical properties of the dissimilarly jointed material [ 41 ].…”

“…In Figure 9 a, Ti and Al are separated owing to delamination at the Ti/Al interface. The delamination of various bonded materials during tensile testing has been frequently reported in the literature [ 39 ]. This phenomenon is closely related to the different plastic strains in each material under the applied stress, and the insufficient diffusion bonding strength produced by the cladding process.…”