Key Laboratory of Liquid Structural Evolution and Processing of Materials (Ministry of Education), Shandong University, Jinan 250061, China.
J Chem Phys. 2013 May 7;138(17):174508. doi: 10.1063/1.4803136.
Recently, we observed an unusual non-monotonic glass relaxation phenomenon, i.e., the three-step sub-T(g) relaxation in hyperquenched CuZrAl glass ribbons [L. N. Hu and Y. Z. Yue, Appl. Phys. Lett. 98, 081904 (2011)]. In the present work, we reveal the origin of this abnormal behavior by studying the cooling rate dependence of the sub-T(g) enthalpy relaxation in two metallic glasses. For the Cu46Zr46Al8 glass ribbons the sub-T(g) enthalpy relaxation pattern exhibits a three-step trend with the annealing temperature only when the ribbons are fabricated below a critical cooling rate. For the La55Al25Ni20 glass ribbons the activation energy for the onset of the sub-T(g) enthalpy relaxation also varies non-monotonically with the cooling rate of fabrication. These abnormal relaxation phenomena are explained in terms of the competition between the low and the high temperature clusters during the fragile-to-strong transition. By comparisons of chemical heterogeneity between Cu46Zr46Al8 and La55Al25Ni20, we predict that the abnormal relaxation behavior could be a general feature for the HQ metallic glasses.
最近，我们观察到一种不寻常的非单调玻璃弛豫现象，即在过冷 CuZrAl 玻璃带中出现的三步亚 Tg 弛豫[L. N. Hu 和 Y. Z. Yue, Appl. Phys. Lett. 98, 081904 (2011)]。在本工作中，我们通过研究两种金属玻璃中亚 Tg 焓弛豫的冷却速率依赖性，揭示了这种异常行为的起源。对于 Cu46Zr46Al8 玻璃带，只有在低于临界冷却速率下制备时，亚 Tg 焓弛豫模式才表现出三步趋势随退火温度的变化。对于 La55Al25Ni20 玻璃带，亚 Tg 焓弛豫的起始激活能也随制备的冷却速率呈非单调变化。这些异常的弛豫现象可以用脆性到强转变过程中低温和高温团簇之间的竞争来解释。通过比较 Cu46Zr46Al8 和 La55Al25Ni20 之间的化学不均匀性，我们预测异常弛豫行为可能是过冷金属玻璃的一个普遍特征。
