Outstanding Tensile Ductility in High Iron-Containing Al-Si-Cu Alloys
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ue to the low ductility caused by the presence of coarse and faceted silicon particles, h-Al2Cu and ironrich intermetallic phases, the use of hypoeutectic Al-SiCu alloys is mainly restricted to the production of nonloading bearing cast parts for the automotive industry, usually engine heads and gearboxes.[1] The presence of iron in Al-Si alloys leads to the formation of iron-rich intermetallic phases, such as aAlFeSi and b-AlFeSi, which induce several defects and severely impair the ductility of cast parts. In addition, the existent techniques for iron removal from the metal
BRENDA JULIET MARTINS FREITAS and CLAUDEMIRO BOLFARINI are with the Department of Materials Engineering (DEMa), Federal University of Sa˜o Carlos (UFSCar), Rodovia Washington Luı´ s, km 235, Sa˜o Carlos, SP 13565-905, Brazil and also with the Graduate Program in Materials Science and Engineering (PPGCEM), Federal University of Sa˜o Carlos (UFSCar), Rodovia Washington Luı´ s, km 235, Sa˜o Carlos, SP 13565-905, Brazil. Contact e-mail: [email protected]. ALBERTO MOREIRA JORGE JUNIOR, GUILHERME ZEPON, CLAUDIO SHYINTI KIMINAMI and WALTER JOSE´ BOTTA are with the Department of Materials Engineering (DEMa), Federal University of Sa˜o Carlos (UFSCar). Manuscript submitted December 9, 2019.
METALLURGICAL AND MATERIALS TRANSACTIONS A
bath are not economically feasible, limiting the use of recycled alloys to the casting sector.[2–4] The microstructure of cast Al-Si alloys also exhibits plate-like eutectic silicon that can be refined by the addition of strontium/sodium or via Si globulization treatment.[4–8] However, even with iron content around the maximum allowed by the AA Standards (0.8 wt pct) and refined/globular silicon particles, conventionally cast 319-aluminum alloys are brittle, presenting elongation to fracture values ranging between 0 and 2 pct at room temperature.[6,9,10] Spray forming is an advanced casting technology that allows the manufacture of aluminum alloys with a refined and homogeneous microstructure that can improve the mechanical properties.[11–15] In the case of the cast Al-alloys the tailored microstructure formed by spray forming allows thermomechanical processing by extrusion or forging, opening a new route for recycling these materials, contributing to the efforts of saving raw materials, energy and reducing the pollution levels caused by the aluminum industry.[10,16–19] Besides allowing mechanical processing, previous studies[10,20] showed that spray forming followed by rotary swaging route, hereinafter called SF + RS, applied in high iron-containing 319-aluminum alloys is capable of significantly improve the tensile ductility (6 to 8 pct) in comparison to the cast counterpart, due to alloy homogeneity and microstructural refinement. An approach widely used to enhance ductility of Alalloys in the last decades is via intragranular precipitation of nanoparticles, which favor the splitting of the plastic strain induced by deformation within grains and reduces the tendency of stress concentration at the grain boundaries and on the mat
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