Exploration Of Glass Transition Characteristic And GFA Of Zr-based BMGs With Electrical Resistivity Method

With so many excellent capabilities, bulk metallic glasses (BMGs) exhibit not only extensive applications in the engineering field but also important effect on the basic study field. The glass transition and the glass-forming ability (GFA) are the focus for developing new BMGs and studying the basic theory all the time. This paper has reviewed the method in establishing T_g of BMGs, pointed out its perplexities, emphasized the need for searching a new method, and investigated the glass transition characteristic and GFA of Zr-based BMGs mainly by the electrical resistivity method.Firstly, based on the experimental results of ZrAlNiCu (Nb,Ti) BMGs, we pointed out the need for standardizing the electrical resistivity method to determine glass transition temperature and also explained how to determine it in detail. On the reduced electrical resistivity temperature curve, we defined three kinds of characteristic temperature related to glass transition, T_g-dep1, T_g-int and T_g-dep2. By comparing T_g determined by the electrical resistivity and DSC method, we have found that, for the same alloy at the same heating rate, T_g-dep1, T_g-int and T_g-dep2 determined by the former method are very close to T_g-onset , T_g-mid and T_g-end obtained by the latter, respectively. The result validates the feasibility of electrical resistivity method. Compared with DSC method, the electrical resistivity method is operated more conveniently in practice and its equipment costs less; Furthermore, when the DSC curves cannot show the character of the glass transition, the reduced electrical resistivity temperature curve can do so. Therefore the electrical resistivity method offers a very useful tool to investigate the glass transition characteristic and the glass-forming ability of BMGs.Additionally, we have theoretically discussed the feasibility of considering the relaxation time of glass transition ((Ï„_Tg)^tot as a criterion of GFA. According to the characteristic temperatures obtained from DSC and electrical resistivity experiments, (Ï„_Tg)^tot is calculated to estimate the GFA of Zr₅₇Al₁₀Ni_12.6Cu_15.4Nb₅ and Zr_52.5Ti₅Al₁₀Ni_14.6Cu_17.9 BMGs. The result is consistent with that obtained by glass transition temperature and the supercooled region criterions, which demonstrates that Ï„_Tg^tot is efficacious to indicate the GFA of BMGs.Finally, based on Lasocka relation and Kissinger equation we have investigated the relationship between the kinetic characteristic of glass transition,the structural characteristic of BMGs and GFA of BMGs, which will bring some inspiration to understand the glass transition characteristic and GFA of BMGs.