Université de Lyon, CNRS , Lyon, France.
J Phys Chem B. 2013 Oct 31;117(43):13658-66. doi: 10.1021/jp4067179. Epub 2013 Oct 10.
The relaxational dynamics in metallic glasses (MGs) is investigated by using mechanical spectroscopy. The spectra show that in MGs there are two relaxations: (i) the α relaxation, linked to the glass transition, as observed in other classes of amorphous materials; and (ii) the β relaxation, well observed below the glass transition, with an intensity strongly dependent on the MG composition, the nature of which has been linked to the local microstructure of MGs. For the investigated MGs we find that the intensity and relaxation time of the β relaxation depends, in a reproducible fashion, on the thermal history of the samples. During aging experiments, the intensity decreases (as well as the τβ) with a time dependence described well by a stretched exponential, with an exponent β(aging) independent of the driving frequency. Moreover, we find that the activation energy Uβ and the peak temperature Tβp of the β relaxation follow the approximate relationship: Uβ ≈ 31.5RTβp (for driving frequency 1 Hz), indicating that the high temperature limit of the peak frequency is approximately the same for all the MGs investigated. Finally, the frequency separation of the α and β processes in the mechanical loss spectra for La-and Pd-based metallic glasses is tested against the prediction of the Coupling Model.
采用力学谱研究了金属玻璃（MGs）中的弛豫动力学。谱表明，在 MGs 中有两种弛豫：（i）与玻璃转变有关的α弛豫，如在其他非晶态材料中观察到的；和（ii）β弛豫，在玻璃转变以下很好地观察到，其强度强烈依赖于 MGs 的组成，其性质与 MGs 的局部微观结构有关。对于所研究的 MGs，我们发现β弛豫的强度和弛豫时间以可重复的方式依赖于样品的热历史。在老化实验中，强度随着时间的推移而降低（τβ也是如此），其时间依赖性很好地由扩展指数描述，指数β（老化）与驱动频率无关。此外，我们发现β弛豫的激活能 Uβ和峰值温度 Tβp 遵循近似关系：Uβ≈31.5RTβp（驱动频率为 1 Hz），表明所有研究的 MGs 的峰值频率的高温极限大致相同。最后，针对耦合模型，对 La 和 Pd 基金属玻璃的力学损耗谱中α和β过程的频率分离进行了测试。
