A new microstructure model is developed for amorphous alloys,so called Cluster medel, in which the amorphous phase is thought of composing of randomly distributed ordered clusters of different sizes.Thermodynamic calc...A new microstructure model is developed for amorphous alloys,so called Cluster medel, in which the amorphous phase is thought of composing of randomly distributed ordered clusters of different sizes.Thermodynamic calculation on this model deduces a parameter describing the glass forming ability of metallic alloys:α_c=(1-2.08/Φ_m)T_g/T_m,where T_g is gass transition temperature,T_m is the melting temperature,and Φ_m is entralpy change of melting.It is believed that easy glass forming alloy systems have larger values of a_c.This new criterion of GFA not only provides the theoretical background for several GFA criteria in the literature cited,but also can predict the GFA of many alloy systems more reasonably and accurately.展开更多
The thermodynamic model of multicomponent chemical short range order (MCSRO) was established in order to evaluate the glass forming ability (GFA) of ternary alloys. Comprehensive numerical calculations using MSCRO sof...The thermodynamic model of multicomponent chemical short range order (MCSRO) was established 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 100?K/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.展开更多
Key step of exploiting a new type BMG (Bulk Metallic Glass) is quickly judging GFA (Glass Forming Ability) of the alloys. The mole melting heats of BMGs are calculated using the weighted averages principle. The reliab...Key step of exploiting a new type BMG (Bulk Metallic Glass) is quickly judging GFA (Glass Forming Ability) of the alloys. The mole melting heats of BMGs are calculated using the weighted averages principle. The reliability and limitation of Trg criterion for GFA are discussed. The reason why Trg of BMGs is larger than 0.5 is discussed. Two new criteria for GFA, ΔHmg and ΔGg, are proposed. GFA sequence of BMGs is calculated using the ΔHmg criterion, the result agrees with that of A. Inoue and the Rc criterion. Furthermore, as an example, the Rc of the alloys developed by Chuang DONG et al is calculated using the ΔHmg and ΔGg. The ascending sequence of these alloys calculated with the ΔHmg criterion agrees with that of Chuang DONG et al. On the contrary, the result by the ΔGg criterion is in contrary with Chuang DONG et al, indicating that the ΔHmg criterion is better and more convenient than the ΔGg criterion. Calculation showed that the optimum ΔHmg is -15.16 kJ/mol.展开更多
A ferromagnetic amorphous Fe73Al4Ge2Nb1P10C6B4 alloy with high glass-forming ability was synthesized by melt spinning. The supercooled liquid region before crystallization reaches about 65.7 K. The crystallized struct...A ferromagnetic amorphous Fe73Al4Ge2Nb1P10C6B4 alloy with high glass-forming ability was synthesized by melt spinning. The supercooled liquid region before crystallization reaches about 65.7 K. The crystallized structure consists of alpha -Fe, Fe3B, FeB, Fe3P and Fe3C phases. The Fe-based amorphous alloy exhibits good magnetic properties with a high saturation magnetization and a low saturated magnetostriction. The crystallization leads to an obvious decrease in the soft magnetic properties.展开更多
文摘A new microstructure model is developed for amorphous alloys,so called Cluster medel, in which the amorphous phase is thought of composing of randomly distributed ordered clusters of different sizes.Thermodynamic calculation on this model deduces a parameter describing the glass forming ability of metallic alloys:α_c=(1-2.08/Φ_m)T_g/T_m,where T_g is gass transition temperature,T_m is the melting temperature,and Φ_m is entralpy change of melting.It is believed that easy glass forming alloy systems have larger values of a_c.This new criterion of GFA not only provides the theoretical background for several GFA criteria in the literature cited,but also can predict the GFA of many alloy systems more reasonably and accurately.
文摘The thermodynamic model of multicomponent chemical short range order (MCSRO) was established 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 100?K/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.
文摘Key step of exploiting a new type BMG (Bulk Metallic Glass) is quickly judging GFA (Glass Forming Ability) of the alloys. The mole melting heats of BMGs are calculated using the weighted averages principle. The reliability and limitation of Trg criterion for GFA are discussed. The reason why Trg of BMGs is larger than 0.5 is discussed. Two new criteria for GFA, ΔHmg and ΔGg, are proposed. GFA sequence of BMGs is calculated using the ΔHmg criterion, the result agrees with that of A. Inoue and the Rc criterion. Furthermore, as an example, the Rc of the alloys developed by Chuang DONG et al is calculated using the ΔHmg and ΔGg. The ascending sequence of these alloys calculated with the ΔHmg criterion agrees with that of Chuang DONG et al. On the contrary, the result by the ΔGg criterion is in contrary with Chuang DONG et al, indicating that the ΔHmg criterion is better and more convenient than the ΔGg criterion. Calculation showed that the optimum ΔHmg is -15.16 kJ/mol.
文摘A ferromagnetic amorphous Fe73Al4Ge2Nb1P10C6B4 alloy with high glass-forming ability was synthesized by melt spinning. The supercooled liquid region before crystallization reaches about 65.7 K. The crystallized structure consists of alpha -Fe, Fe3B, FeB, Fe3P and Fe3C phases. The Fe-based amorphous alloy exhibits good magnetic properties with a high saturation magnetization and a low saturated magnetostriction. The crystallization leads to an obvious decrease in the soft magnetic properties.
