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.