Damping of Fe-Al Alloy Electrodeposited in an Ionic Liquid

Iron-Aluminium alloys were produced by the electro-deposition of iron-aluminium on a copper substrate. The electro-deposition process was done in the ionic liquid 1-butyl-1-methylpyrrolidinium trifluoromethylsulfonate, [Py1,4]TfO. A solution of (0.2 M FeCl2 + 2.75 M AlCl3)/ [Py1,4] TfO was used at a temperature of T=363 K because this mixture is solid at room temperature. Electrodeposited samples were studied by means of mechanical spectroscopy, differential thermal analysis and laser light microscopy. Mechanical spectroscopy studies were performed as a function of temperature, frequency and strain. The usual damping peaks for copper, low temperature grain boundary peak, recovery peak and intermediate temperature grain boundary peak were observed. In addition, a new damping peak at around 800 K which is not thermally activated was discovered. The physical mechanism controlling the appearance of this new peak is the dissolution of small precipitates or agglomerates of defects which take place at around 800 K during the warming and the subsequent re-precipitation/re-agglomeration during the cooling. This process could occur either in the copper substrate or at the Fe-Al electrodeposit.本研究通过电沉积法在铜基底（copper substrate）上沉积铁铝合金层，制备得到铁铝合金试样。该电沉积过程在离子液体（ionic liquid）1-丁基-1-甲基吡咯烷鎓三氟甲磺酸盐（[Py1,4]TfO）中进行。由于(0.2 M FeCl₂ + 2.75 M AlCl₃)/[Py1,4]TfO混合体系在室温下呈固态，故实验采用该电解液，并将反应温度维持在363 K。对所得电沉积试样，研究人员采用力学谱（mechanical spectroscopy）、差热分析（differential thermal analysis）及激光显微成像技术进行表征；其中力学谱测试以温度、频率与应变为变量展开。实验观测到了铜基体典型的阻尼峰：低温晶界峰、回复峰以及中温晶界峰。此外，本研究还发现了一处位于800 K附近的新型阻尼峰，该峰不具备热激活特性。调控该新型阻尼峰出现的物理机制为：升温至800 K附近时，微小析出相或缺陷团聚体发生溶解；降温过程中则会发生再析出或缺陷的再团聚，该过程既可发生于铜基底内部，也可出现在铁铝电沉积层中。