Effect of the cooling rate on the mechanical properties of Ti-Ni-Cu-Zr-based crystal/glassy alloys

Ti-Ni-Cu-Zr-based crystal/glassy dual-phase alloy samples with different sizes and good mechanical properties were manufactured. The structure of these samples was examined via X-ray Diffraction, Scanning Electron Microscopy, and Transmission Electron Microscopy. The developed dual-phase structure alloys combine the high strength of glassy alloys and plasticity of crystalline alloys. Plastic deformation was enhanced by this dual-phase structure. Mechanical characterization of the alloys revealed three deformation stages, namely a martensitic transformation, dislocation slip in a crystalline phase, and shear deformation of the glassy matrix. Two types of effects involving the martensitic transformation were observed: superelastic behavior and the transformation induced plasticity (TRIP) effect, which provide an additional deformation mechanism and lead to a significant increase in the plasticity of these dual-phase samples. The results indicate that the fraction of glassy phase occurring in large rods formed at lower cooling rates is lower than that occurring in smaller rods; therefore, the deformation-induced martensitic transformation of the crystalline cP2 phase in the large samples occurs at lower stresses.