Bulk metallic glass formation in Zr$_{65}$Cu$_{27}$Ti$_{8}$ Alloys

Although bulk glass (BMG) formation has been reported in Cu- rich Cu-Zr alloys, it has not been observed in the Zr-rich alloys. Here, we report that the substitution of Ti for Cu in Zr$_{65}$Cu$_{35}$ alloys dramatically improves glass formation, giving Zr$_{65}$Cu$_{27}$Ti$_{8}$ bulk metallic glasses with diameters up to 1mm by suction casting. However, the onset crystallization temperatures and the widths of the supercooled liquid region are reduced with the introduction of Ti, due to the formation of a metastable icosahedral quasicrystal at lower crystallization temperatures in the glasses made with Ti. These observations suggest the formation of icosahedral short-range order in the supercooled liquid alloy, which increases the nucleation barrier for the Zr$_{2} $Cu phase during the quench and makes glass formation easier. This is supported by results from recent in-situ measurements of the supercooled liquid structures of Zr-Ti-Cu-Ni-Al alloys.