Fabrication, characterization and tensile property of a novel Ti₂Ni/TiNi micro-laminated composite

A novel Ti₂Ni/TiNi laminated composite has been fabricated by diffusion bonding using Ti foils and Ni foils under the protection of argon gas at 900°C. The effect of diffusion time on the microstructure of the composite was investigated. The results indicate that with the increase of diffusion time, Ti and Ni foils were gradually consumed while forming different intermetallics (Ti₂Ni, TiNi, Ni₃Ti). When the diffusion time reached 36h, the final composite consisting of alternative layers of Ti₂Ni and TiNi was fabricated. XRD results reveal that TiNi layer in Ti₂Ni/TiNi laminated composite has a complex monoclinic B19'-type crystal structure and DSC results show that A_s, A_f, M_s, M_f and transition hysteresis temperature of the composite are 83.3°C,106.7°C,71.8°C,51.2°C and 35.7°C, respectively. The tensile experiment reveals that the Ti₂Ni/TiNi laminated composite exhibits a high ultimate tensile strength of 790MPa and a high elongation of 9.3% which overcomes the brittleness of Ti₂Ni. The formation of transverse cracks in brittle Ti₂Ni layers getting arrested at ductile TiNi layers, the deflection and the connection of consequently produced cracks caused the delamination and final fracture of the whole composite.