Investigation of Solidification and Precipitation Behavior of Si-Modified 7075 Aluminum Alloy Fabricated by Laser-Based
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ASED powder bed fusion (L-PBF), also known as selective laser melting (SLM), is a powder-based additive manufacturing (AM) technique utilizing a laser as the energy source, allowing to manufacture complex-shaped metal components by additive consolidation of powder layers.[1] Compared to conventional subtractive manufacturing processes, AM offers immanent advantages for medium-low batch production, owing to its capability to fabricate customized and complex-shaped parts as an integral piece without the need for expensive molds and tooling.[2] Moreover, due to the steep thermal gradients and high
GUICHUAN LI, SURAJ DINKAR JADHAV, MARIA L. MONTERO-SISTIAGA, JEROEN SOETE, and KIM VANMEENSEL are with the Department of Materials Engineering, KU Leuven, Kasteelpark Arenberg 44, 3001 Heverlee, Belgium. Contact e-mail: [email protected] ARTURO MARTI´N and CARMEN M. CEPEDA-JIME´NEZ are with the IMDEA Materials Institute, C/Eric Kandel, 2, 28906 Getafe, Madrid, Spain. MARIA SAN SEBASTIAN is with the IK4 LORTEK Technological Centre, Arranomendia 4A, 20240 Ordizia, Spain. Manuscript submitted May 5, 2020; accepted October 17, 2020.
METALLURGICAL AND MATERIALS TRANSACTIONS A
cooling rates during L-PBF, 3D-printed components exhibit enhanced mechanical performance. L-PBF processed metals owe their enhanced strength to the presence of supersaturated solid solutions and non-equilibrium phases, as well as to their refined solidification microstructures with high dislocation densities.[3] The formation of a supersaturated matrix in L-PBF processed aluminum alloys offers opportunities to further improve the strength by precipitation during subsequent heat treatment. This is particularly interesting in the 2xxx, 6xxx, and 7xxx series aluminum alloys, as they obtain their mechanical strength from the precipitate formation during post-heat treatments. High strength Al-Zn-Mg-Cu alloys, especially AA7075 aluminum alloys, are widely used for the fabrication of structural components in the automotive and aerospace industries due to their high specific strength and good fatigue properties.[4,5] However, traditional cold deformation manufacturing techniques are unable to fabricate AA7075 aluminum alloy components with complicated geometries because of their poor formability and high elastic spring back.[6] Due to its inherent layer-by-layer building fashion, L-PBF offers completely new opportunities to design and manufacture metallic structures and components with
high complexity and precision.[7] Unfortunately, the widespread application of L-PBF as a manufacturing technique to fabricate high strength Al-Zn-Mg-Cu alloys is hindered by solidification cracking, also known as hot tearing. A major contributor to this phenomenon is the large solidification interval, extended under rapid cooling conditions, that is characteristic for this type of alloys.[8] The extensive vaporization of the main strengthening alloying elements, i.e., Zn and Mg, as a result of their high equilibrium vapor pressure and low boiling point, during the L-PBF process, re
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