Microstructural Assessment of a Multiple-Intermetallic-Strengthened Aluminum Alloy Produced from Gas-Atomized Powder by Hot Extrusion and Friction Extrusion

Abstract

An aluminum (Al) matrix with various transition metal (TM) additions is an effective alloying approach for developing high-specific-strength materials for use at elevated temperatures. Conventional fabrication processes such as casting or fusion-related methods are not capable of producing Al–TM alloys in bulk form. Solid phase processing techniques, such as extrusion, have been shown to maintain the microstructure of Al–TM alloys. In this study, extrusions are fabricated from gas-atomized aluminum powders (≈100–400 µm) that contain 12.4 wt % TM additives and an Al-based matrix reinforced by various Al–Fe–Cr–Ti intermetallic compounds (IMCs). Two different extrusion techniques, conventional hot extrusion and friction extrusion, are compared using fabricating rods. During extrusion, the strengthening IMC phases were extensively refined as a result of severe plastic deformation. Furthermore, the quasicrystal approximant IMC phase (70.4 wt % Al, 20.4 wt % Fe, 8.7 wt % Cr, 0.6 wt % Ti) observed in the powder precursor is replaced by new IMC phases such as Al3.2Fe and Al45Cr7-type IMCs. The Al3Ti-type IMC phase is partially dissolved into the Al matrix during extrusion. The combination of linear and rotational shear in the friction extrusion process caused severe deformation in the powders, which allowed for a higher extrusion ratio, eliminated linear voids, and resulted in higher ductility while maintaining strength comparable to that resulting from hot extrusion. Results from equilibrium thermodynamic calculations show that the strengthening IMC phases are stable at elevated temperatures (up to ≈ 600 °C), thus enhancing the high-temperature strength of the extrudates.

Parameters, Properties, and Process: Conditional Neural Generation of Realistic SEM Imagery Toward ML-Assisted Advanced Manufacturing

“…We develop generative models trained on SEM images of aluminum alloy AA7075 tubes manufactured via the Shear-Assisted Processing and Extrusion (ShAPE) technology [7,8]. ShAPE is an emerging advanced manufacturing process that an synthesize rods, bars, tubes, and wires [9][10][11][12] of different cross-sectional areas and shapes from metallic (pure metals, alloys) feedstock in various forms such as powders, chips, films, discs, and solid billets [13][14][15]. ShAPE-synthesized parts demonstrate unique microstructures with minimal porosity and never-before-seen performance.…”

Shear-Deformation-Induced Modification of Defect Structures and Hierarchical Microstructures in Miscible and Immiscible Alloys

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Shear-based deformation is used for several advanced materials' processing methods such a friction-stirbased processing, welding, or additive manufacturing [1][2][3][4][5]. In these processes, the mechanical-thermal coupling obscures a deep mechanistic understanding of the microstructural evolution of multi-phase metallic systems under extreme shear deformation, and the knowledge of how these microstructures influence mechanical properties is in its nascency (Figure 1).

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