Correlation of glass-forming ability to thermal properties in Ti-based bulk metallic glasses

Ti_45.8Zr_6.2Cu_45-xNi _xSn₂Si₁ (x = 0, 2, 4, 5, 7, 9, 11, 13 and 15 at.%) and Ti_52-yZr_yCu_40.9Ni _5.1Sn₂ (y = 4, 6, 8, 10, 12, 14 and 16 at.%) bulk metallic glasses with critical diameters up to 4 mm were prepared by copper mold casting. The thermal properties and crystallization behavior of these Ti-based glassy alloys have been investigated in detail. It is shown that the higher the onset temperature of the last crystallization event (T_n), the larger the glass forming ability (GFA). By considering the comprehensive effect of glass transition temperature (T_g), the onset temperature of the first crystallization event (T_x), T_n and liquidus temperature (T_l), we proposed a parameter N = (2T_x - T_g + T_n)/2T_l for the evaluation of GFA. It is found that this criterion is particularly effective for the BMGs which show multistage crystallization events upon heating.