Abstract: The thermodynamic model of multicomponent chemical short range order (MCSRO) wasestablished in order to evaluate the glass forming ability (GFA) of ternary alloys. Comprehensive numerical calculations using MSCRO software were conducted to obtain the composition dependence of the MCSRO undercooling in Zr-Ni-Cu, Zr-Si-Cu and Pd-Si-Cu ternary systems. By the MCSRO undercooling principle, the composition range of Zr-Ni-Cu system with optimum GFA is determined to be 62.5～75 Zr, 5～20 Cu, 12.5～25 Ni ( n (Ni)/ n (Cu)=1～5). The TTT curves of Zr-Ni-Cu system were also calculated based on the MCSRO model. The critical cooling rates for Zr-based alloy with deep MSCRO undercooling are estimated to be as low as 100K/s, which is consistent with the practical cooling rate in the preparation of Zr-based bulk metallic glass (BMG). The calculation also illustrates that the easy glass forming systems such as Pd-based alloys exhibit an extraordinary deep MCSRO undercooling. It is shown that the thermodynamic model of MCSRO provides an effective method for the alloy designing of BMG.

Key words:  thermodynamic model; multicomponent chemical short range order (MCSRO); undrcooling; bulk metallic glasses (BMG); glass forming ability (GFA), Zr-Ni-Cu system