Work-hardening mechanisms of the Ti₆₀Cu₁₄Ni₁₂Sn₄Nb₁₀ nanocomposite alloy

The work-hardening mechanisms of the Ti₆₀Cu₁₄Ni₁₂Sn₄Nb₁₀ nanocomposite alloy were studied. This material is composed of micrometer-sized dendrites embedded in a nanostructured eutectic matrix and a CuTi₂ intermetallic phase. Our study shows that, in the as-quenched state, the nanostructured eutectic matrix behaves softer than the dendrites. During mechanical deformation, both the dendrites and the eutectic matrix harden, whereas the hardness of the CuTi₂ intermetallic phase remains unaltered. The high strength of the dendrites is caused by the interplay between solid solution hardening and dislocation networks during plastic flow. Interestingly, the mechanical hardening of the nanoeutectic matrix is also assisted by a martensitic transformation of the NiTi phase. Transmission electron microscopy studies clearly show that the martensitic transformation of this phase is accompanied with grain size refinement, which also plays a role in the deformation-induced mechanical hardening.