Abstract
Al-x wt.% Fe bulk alloys were fabricated from a powder mixture of pure Al and x wt.% of Fe, where x = 2 wt.%, 5 wt.% and 10 wt.%. Initially, as-mixed mixtures were processed using a mechanical-alloying (MA) technique in an attritor for 4 h. The milling was performed in an argon atmosphere at room temperature followed by the sintering of the milled powders in a high-frequency induction furnace to produce bulk samples. Scanning electron microscopy (SEM) was used to study the morphology of the produced alloys, and X-ray diffraction (XRD) to determine the phases formed after the sintering process and their crystallite size. The corrosion behavior of the fabricated samples was studied by immerging them in a 3.5% sodium chloride (NaCl) solution at room temperature using cyclic-polarization (CP) and electrochemical-impedance-spectroscopy (EIS) techniques. The SEM results showed that Fe was uniformly distributed in the Al matrix, and XRD revealed the formation of Al and intermetallic, i.e., Al6Fe and Al13Fe4, phases in the Al-Fe alloys after sintering. The hardness of the Al-Fe alloys was increased with the addition of Fe due to the formation of intermetallic compounds. Electrochemical results showed that there was a proportional relationship between the percentage of Fe additives and corrosion potential (Ecorr) where it shifted toward a nobler direction, while corrosion current density (icorr) and corrosion rate decreased with an increasing Fe%. This observation indicates that the addition of Fe into an Al matrix leads to an improvement in the corrosion resistance of the alloys.
Highlights
The mechanical-alloying (MA) technique is used to fabricate bulk metallic alloys from elemental powders that demonstrate better physical and mechanical properties when compared with similar alloys produced using a conventional manufacturing process [1,2,3]
The Scanning electron microscopy (SEM) micrographs with the corresponding energy-dispersive spectrometry (EDS) analysis of pure Al and Al-10 wt.% Fe alloys after the sintering process are shown in Figure 2a,b, respectively
Uniform distribution of Fe in an Al matrix was revealed by Field emission scanning electron microscope (FESEM) and EDS mapping, achieved by the combined process of MA and HFIS
Summary
The mechanical-alloying (MA) technique is used to fabricate bulk metallic alloys from elemental powders that demonstrate better physical and mechanical properties when compared with similar alloys produced using a conventional manufacturing process [1,2,3]. Coatings 2019, 9, 686 processes, such as consolidation and sintering, in order to produce a homogeneous structure It has been reported in the literature that the MA technique leads to the production of stable microstructures in terms of the uniform dispersion of oxides, and produces alloys with fine-grain structures [4]. It was reported that transition metals are not freely miscible in Al, for example, the solubility of Fe in Al can reach the maximum level of 0.03%, which delays the age-hardening process [10,11] Nonequilibrium processes, such as mechanical-alloying and rapid-solidification techniques, are used to increase the solubility of Fe in an α-Al matrix [12,13,14,15,16]. The corrosion resistance of nanocrystalline and coarse-grained Al was affected, as it was reported that the formation of pits on the alloy surface resulted in higher corrosion than the values obtained from the coarse-grained material. Coatings 2019, 9, x FOR PEER REVIEW immerging them in a 3.5% NaCl solution for 1 h via cyclic-polarization (CP) and electrochemicalimpedance-spectroscopy (EIS) techniques
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