Enhancement of Mechanical Properties of Aluminum and 2124 Aluminum Alloy by the Addition of Quasicrystalline Phases

Abstract

A structural and mechanical characterization of pure aluminum and 2124 T6 aluminum alloy reinforced with quasicrystalline phases of composition Al 65 Cu 20 Fe 15 and Al 70.5 Pd 21 Mn 8.5 (%at.) were performed. The quasicrystalline phases were synthesized by arc melting and then milled to produce powder of the alloys, which were then mechanical mixed with the starting powders of aluminum and 2124 aluminum alloy. The composites were produced by hot extrusion of a mechanical mixture containing 20% (%wt.) of the reinforcing phases on the metallic matrix. The structural characterization of the composites was carried out by X-ray diffraction, scanning electron microscopy and transmission electron microscopy. Mechanical characterization was carried out by Vickers hardness measurements and torsion tests at room temperature. The pure aluminum/quasicrystal composite showed the presence of the same phases from the starting powder mixture while for the 2124 aluminum alloy/Al 65 Cu 20 Fe 15 the quasicrystalline phase transformed to the tetragonal ω-Al 7 Cu 2 Fe during the solution heat treatment. Mechanical strength of the composites presented a substantial increase in comparison to the original matrix metal. While the equivalent ultimate tensile strength of the Al/quasicrystal composites reached values up to 215MPa and Vickers hardness up to 60HV, the 2124/quasicrystal composites reached values up to 670MPa and Vickers hardness up to 190HV.

Consolidation of magnesium and magnesium-quasicrystal composites through high‑pressure torsion

“…These properties are associated to their complex atomic organization [19]. To this date, MMCs reinforced with quasicrystals have been only fabricated by thermally assisted processes, involving solidification [20,21] or hot consolidation of mechanically mixed powders [22]. In this work, we fabricate this composite by cold consolidation.…”

Recent developments on fabrication of Al‐matrix composites reinforced with quasicrystals: From metastable to conventional processing

“…Although most of the studies about MMCs reinforced with stable quasicrystals are based on the Al-Cu-Fe system, a few have also fabricated Al-matrix composites reinforced with Al-Pd-Mn-based quasicrystals using hot extrusion [70] and Al-Cu-Cr-Fe-based quasicrystals using SPS or uniaxial compression [112,113,114]. In these studies, the same type of coarse particle reinforcement was observed.…”

“…The "stable" quasicrystals reinforcing a metallic matrix are mostly fabricated by powder metallurgy. In this case, the quasicrystal is produced either by gas-atomization or mechanical alloying, and then, the composite can be fabricated by different methods that can include: a mechanical mixture of powders to be subsequently consolidated [70], deposited onto a substrate by thermal spraying [40], spray formed [71], conventionally casted [72], and more recently by additive manufacturing [73]. In turn, MMCs reinforced with "metastable" quasicrystals need to be processed using rapid solidification techniques since they only form under these conditions.…”

“…Other authors have also tried this approach [110,111]; however, they report a complex microstructure formed after matrix solidification due to partial dissolution of the quasicrystalline particles. Figure 6(d) shows a composite microstructure fabricated by hot-extrusion [70]. This latter microstructure shows wavelike patterns of the reinforcing phase.…”

Formation and stability of complex metallic phases including quasicrystals explored through combinatorial methods

“…Since the discovery of quasicrystals (QCs) by D. Shechtman et al . 1 , more than a hundred metallic systems were found to form quasicrystalline phases such as Al-Cu-Fe 2–4 , Al-Cu-Fe-Cr 5 , Al-Fe-Cr-(TM = transition metal) 6–8 , Al-Mn-(TM) 9,10 , Al-Ni-Fe 11 and Al-Ni-Co 12,13 . As the formation motifs of QCs are to a large extent due to geometry, size differences and size ratio of constitutive elements, QCs usually form in narrow composition ranges 13 , and are often metastable 7 .…”