Enhancement of the glass forming ability of superelastic Ni-Ti-Cu-Zr-Si alloy

In this study, the use of (Ni0.35Ti0.30Cu0.15Zr0.20)100−xSix (x = 0, 0.5, 1.0, 2.0 at%) alloy as a metallic glass precursor for a superelastic alloy, following thermoplastic forming, is investigated. The addition of Si improved the glass forming ability such that a fully amorphous sample with a thickness of ~450 µm was obtained with the x = 2.0 at% alloy. The addition of Si effectively stabilises the supercooled liquid by significantly increasing the activation energy of glass transition. The incubation time, τ, increased from 89 s for the x = 0 alloy to 346 s for the x = 2.0 at% alloy. The parameters relevant to superelastic effects, such as the maximum indentation depth (Dmax) and remnant indentation depth (Drem), remained almost constant. However, the remnant depth ratio increased slightly with the addition of Si. The fabrication of millimetre-scale Ni-Ti-Cu-Zr-Si metallic glass was achieved via the hot pressing of overlapped as-cast plates.