Makarov A S, Qiao J C, Kobelev N P, Aronin A S, Khonik V A
Department of General Physics, State Pedagogical University, Lenin St. 86, Voronezh, 394043, Russia.
School of Mechanics, Civil Engineering and Architecture, Northwestern Polytechnical University, Xi'an 710072, People's Republic of China.
J Phys Condens Matter. 2021 May 28;33(27). doi: 10.1088/1361-648X/abfc6c.
Fragility constitutes a major parameter of supercooled liquids. The phenomenological definition of this quantity is related to the rate of a change of the shear viscosityat the glass transition temperature. Although a large number of correlations of the fragility with different properties of metallic glasses were reported, an adequate understanding of its physical nature is still lacking. Attempting to uncover this nature, we performed the calculation of the fragility within the framework of the interstitialcy theory (IT) combined with the elastic shoving model. We derived an analytical expression for the fragility, which shows its relation with the high-frequency shear modulusin the supercooled liquid state. To verify this result, specially designed measurements ofandwere performed on seven Zr-, Cu- and Pd-based metallic glasses. It was found that the fragility calculated from shear modulus relaxation data is in excellent agreement with the fragility derived directly from shear viscosity measurements. We also calculated the heat capacity jump Δat the glass transition and showed that it is related to the fragility and, consequently, to shear modulus relaxation. The Δ-value thus derived is in a good agreement with experimental data. It is concluded that the fragility and heat capacity jump in the supercooled liquid state can be determined by the evolution of the system of interstitial-type defects frozen-in from the melt upon glass production, as suggested by the IT. This connection is mediated by the high-frequency shear modulus.
脆性是过冷液体的一个主要参数。该量的唯象定义与玻璃化转变温度下剪切粘度的变化率有关。尽管已经报道了大量关于脆性与金属玻璃不同性质之间的相关性，但对其物理本质仍缺乏充分的理解。为了揭示这种本质，我们在间隙原子理论（IT）与弹性推挤模型相结合的框架内进行了脆性计算。我们推导了脆性的解析表达式，该表达式显示了其与过冷液态高频剪切模量的关系。为了验证这一结果，我们对七种锆基、铜基和钯基金属玻璃进行了专门设计的测量。结果发现，由剪切模量弛豫数据计算得到的脆性与直接从剪切粘度测量得到的脆性非常吻合。我们还计算了玻璃化转变时的热容跃变Δ，并表明它与脆性相关，进而与剪切模量弛豫相关。由此得到的Δ值与实验数据吻合良好。结论是，如间隙原子理论所表明的，过冷液态中的脆性和热容跃变可以由玻璃形成时从熔体中冻结的间隙型缺陷系统的演化来确定。这种联系是由高频剪切模量介导的。
