Journal of Advanced Materials in Engineering (Esteghlal)

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Solid Assisted Melt Disintegration (SAMD) is a relatively new method for producing metallic powder particles in which the kinetic energy transferred from a rotating impeller to the melt via a solid medium causes melt disintegration. These droplets are then solidified and separated from the media to obtain metallic powder particles. In the present study, sodium chloride (NaCl) was used to produce Al-6wt%Si powder particles. A specified amount of NaCl was introduced into the aluminum alloy melt and the slurry was stirred following a specified time-temperature regime to disintegrate the molten alloy into droplets. This blend was quenched in water to solidify Al powder particles and to dissolve NaCl in water. The Al powder particles were then collected, washed, dried, and subjected to laser particle size (LPS) analysis and scanning electron microscopy (SEM). The effects of different time-temperature regimes on the size and morphology of the resultant Al-6wt%Si powder particles were investigated and the optimum conditions for obtaining the finest spherical particles were established. It was concluded that the finest and most spherically shaped Al powder particles could be produced by stirring the slurry at 690 °C for 5 min followed by water quenching.

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Despite a great thermodynamic driving force, copper cementation by aluminum from sulfate solutions involves a relatively slow kinetics due to the presence of the passive oxide film on the surface of aluminum. The previous studies have confirmed the positive effect of the presence of small amounts of chloride ion on reducing the scale of this problem. In this paper, the effect of concurrent ball milling on the kinetics of this process has been investigated. The cementation experiments were carried out in a polyamide jar with alumina balls inside by planetary ball milling. The studied parameters were ball number (0, 4), temperature (25-55 °C) and time (0-240 s). All experiments were conducted at constant condition of [Cu²⁺] = 6 g/L, [Cl⁻] = 75 mg/L, rotation speed of 160 rpm, average aluminum particle size of 279 µm and [H⁺] = 1.94×10^-3. The results showed that concurrent ball milling reduces the induction period of the cementation process to less than 120 s.  The apparent rate constant of cementation showed the positive influence of simultaneous milling on the kinetics of the studied cementation process. Moreover, activation energies of the induction and main periods were calculated to be respectively 86 and 26 kJ.mol^-1, indicating the shift of the reaction mechanism from chemical control to mass transfer control.