Local structure and glass transition in Zr-based binary amorphous alloys
Local structure and glass transition in Zr-based binary amorphous alloys
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DOI：
10.2320/matertrans.46.2282
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发表时间：
2005-10
影响因子：
1.2
通讯作者：
T. Ichitsubo;E. Matsubara;J. Saida;H. Chen
中科院分区：
文献类型：
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作者：
T. Ichitsubo;E. Matsubara;J. Saida;H. Chen
通过对非晶态合金的升温速率β、玻璃化转变温度Tg和晶化温度Tx的测量以及对非晶态结构的X射线研究，探讨了差示扫描量热法在金属玻璃中观察到的玻璃化转变的物理意义。在差示扫描量热法(DSC)中，在常规时间尺度的升温速率下，Zr-7-Cu3-0在晶化前发生玻璃化转变，而Zr-7-Ni3-0则立即晶化。在Tg和Tx的两条线性曲线的交点处的升温速率βc与β的关系为我们提供了一个重要的测量来确定金属玻璃的非晶形成能力或热稳定性。当加热温度β大于βc时，即使在Zr7.0Ni30合金中也能观察到明显的玻璃化转变，并抑制了晶化。非晶态合金的热稳定性是由于其非晶态结构不同于Zr2Cu晶相而导致的晶化滞后所致。相反，ZR7.0Ni3.0的热不稳定性归因于其与Zr2Ni晶相的结构相似。因此，抑制晶化是提高现有非晶态合金热稳定性的关键。
The physical significance of the glass transition observed by differential scanning calorimetry (DSC) in the metallic glasses was considered through the measurements of the heating-rate, β, dependence of the glass transition temperature, Tg, and the crystallization temperature, T x , in the Zr 7 0 Cu 3 0 and Zr 7 Ni 3 0 amorphous alloys and X-ray study of their structures in as-quenched and crystallized states. Zr 7 0 Cu 3 0 exhibits the glass transition before crystallization, hut Zr 7 0 Ni 3 0 is immediately crystallized at heating rates of conventional time scale in the DSC measurement. The heating rate β c at the intersection of the two linear curves of T g and T x against log β provides us with a significant measure to determine the glass-forming ability or thermal stability of the metallic glasses. By heating at β larger than β c , the crystallization is suppressed and the glass transition is clearly observed even in Zr 7 0 Ni 3 0 . The thermal stability of the Zr 7 0 Cu 3 0 amorphous alloy is caused by retardation of crystallization due to the amorphous structure that is different from the Zr 2 Cu crystalline phase. In contrast, the thermal instability of Zr 7 0 Ni 3 0 is attributed to the structural similarity to the Zr 2 Ni crystalline phase. Thus, suppressing the crystallization is shown to be a key to enhance the thermal stability of the present amorphous alloys.