An understanding of the electrodeposition process of Al–Mg alloys using an organometallic-based electrolyte

Abstract

Al-Mg alloys were deposited using a baseelectrolyte with the composition Na[AlEt 4 ] ? 2Na[Et 3 Al-H-AlEt 3 ] ? 2.5AlEt 3 ? 6toluene (where Et = -C 2 H 5 ). Mg was introduced into this electrolyte by employing a pure Mg anode. It was found that initially the amount of Mg in the electrolyte increased with the deposition time but eventually a steady state was reached such that the amount of Mg dissolved at the anode became equal to that deposited at the cathode. Compositional and phase analyses indicated that this state is achieved at a critical Mg/Al ratio that resulted in the formation of the hcp Mg-rich phase. By devising various component electrolytes we have attempted to understand the roles of different compounds in the base-electrolyte and have proposed a scheme for the Al-Mg alloy deposition.

Potentiostatic versus galvanostatic electrodeposition of nanocrystalline Al–Mg alloy powders

“…4a), the depositing ions have enough time for arranging themselves in low-energy configurations resulting in featherlike morphology. Interestingly, our recent detailed crystallographic analysis reported elsewhere showed that the featherlike morphology grows with its stem and several higher-order arms oriented in specific crystallographic directions rendering not only morphological but also crystallographic anisotropy to this morphology [9]. At higher applied potential of E=−5 V since the recorded current density value is higher (60 mA cm −2 in Fig.…”

“…Our detailed morphological and microstructural analyses showed that nanocrystalline Al-Mg dendrites appeared with featherlike and globular morphologies [9]. In the present study, we conducted electrodeposition of Al-Mg alloy powders using both potentiostatic and galvanostatic deposition techniques under equal charge conditions.…”

Evolution of Morphology and Microstructure in Electrodeposited Nanocrystalline Al–Mg Alloy Dendrites

“…This shows that an inverse relationship exists between current density and grain size of the depositing morphologies. Our earlier results suggested that the Mg in the electrolyte [15] and thus in the deposits [13] increases with both current density and deposition time. Consistently, the smooth globules possessed higher amount of Mg (~20 at.% Mg) than feather-like morphology (Figure 2(a)).…”

“…The almost constant composition of the smooth globular morphology at ~20 at.% Mg along the length of the dendrite (Figure 2(a)) indicates that this is the solubility limit of the fcc-Al(Mg) phase. With further deposition following the formation of fcc-Al(Mg) phase, the electrolyte was still enriched with Mg [15]. The increased Mg encouraged the nucleation of hcp-Mg(Al) phase with composition ~80 at.% Mg (Figure 6(b) and 2(a)).…”

“…The polished rod was rinsed with DI water and dried before transferring into the glove box. Mg was introduced into the electrolyte by a process which we termed pre-electrodeposition [15]. The Mg enriched electrolyte was used for the actual powder production.…”