Development of thermal plastic forming process for Ti₃₅Zr₁₅Ni₃₅Cu₁₅ metallic glass exhibiting superelasticity after crystallization

In order to enhance the TPF ability of Ti₃₅Zr₁₅Ni₃₅Cu₁₅ metallic glass alloy exhibiting superelasticity after crystallization into the single B2 phase, newly developed “heating TPF process” has been introduced as compared to the conventional “isothermal TPF process”. The result shows that both the surface hologram pattern and superelasticity can be obtained by a one-step heating TPF process under a reasonable condition of target temperature, applied pressure and, processing time. In the case of the heating TPF process, the filling depth generally increases with increasing the compressive load. Besides, during the heating TPF process, the crystallization occurs easily within the processing time of 120 s because of a gradual increase in processing temperature. However, in the case of the isothermal TPF process, though the crystallization can be delayed up to ~1200 s, the complete filling is not achieved even after 1200 s. This result reveals that the heating TPF process is more efficient than the isothermal TPF process. Also, the F_mod parameter, which is a newly modified TPF ability parameter, shows a great correspondence to the experimental result. We confirm the superelasticity of the crystallized B2 phase after the heating TPF process by the nano-indentation test. This result suggests the possibility of further development to effectively combine the superplasticity of metallic glass with superelasticity of B2 phase alloy.