Rebecca A Sweny, Jay F Tressler and Richard P Martukanitz
Experiments were conducted on several alloys representing the Al-Cu-Ag-Mg system to determine the applicability of using these alloys for AM. Alloys were formulated and prepared utilizing a powder blending technique using a pre-alloyed master alloy powder containing Al, Mg, Ti, and Zr with elemental powders of pure Cu and Ag. These powder were processed using laser-based directed energy deposition to produce specimens that were treated to represent the post-process aged only and post-process solution heat treated and aged conditions. Microhardness and microstructural characterization was then conducted. Results of this investigation showed that an aluminum alloy containing between 6 and 8% Cu and 1 to 4% Ag, while also containing 0.3% Mg, Ti, and Zr, displayed excellent response to precipitation strengthening for both post-process treatments. Alloys that were completely solutionized and aged after processing where able to achieve microhardness values exceeding 180 VHN, which are significantly higher than the commonly used Al-10Si-0.5 Mg alloy for AM processes. The high microhardness achieved with the experimental alloy could be attributed to a uniformly distributed network of fine θ’ and Ω precipitates, which was confirmed through TEM. Depending upon the desired post processing treatment (aging only or solutionizing and aging), the results indicate that an alloy composition within this system may be defined to provide optimal strength.
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