Microstructural Development of an AlNiBi Alloy and Influence of the Transient Horizontal Solidification Parameters on Mi
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optimization of microstructures of aluminum-based alloys via solidification processes is considered in the literature to be a fundamental example of the enhancement of mechanical properties[1–35] Obviously, these alloys have gained notoriety due to their excellent resistance/weight ratio, especially in the aerospace and automotive industries, because the HUGO M. AZEVEDO, GABRIEL H. MACHADO, CAROLINA R. BARBOSA, FERNANDO S. ROCHA, ROGE´RIO B. COSTA, and THIAGO A. COSTA are with the Federal Institute of Education, Science and Technology of Para´, IFPA, Almirante Barroso Avenue 1155, Bele´m, PA, 66093-020, Brazil. OTA´VIO L. ROCHA is with the Federal Institute of Education, Science and Technology of Para´, IFPA and also with the Institute of Technology, Federal University of Para´, UFPA, Augusto Correa Avenue 1, Bele´m, PA, 66075-110, Brazil Contact e-mail: [email protected] Manuscript submitted February 21, 2018.
METALLURGICAL AND MATERIALS TRANSACTIONS A
substitution of components with higher specific weight metallic alloys by lighter materials in these industries promotes considerable reductions in the weight of the final product and, as a consequence, increased energy efficiency of manufactured cars and aircraft.[35,36] In this sense, binary Al-Si, Al-Cu, Al-Mg, Al-Sn, Al-Ni, Al-Ag, Al-Bi, and Al-Mg alloys and multicomponent Al-Si-Mg, Al-Si-Cu, Al-Cu-Mg, Al-Cu-Mn, Al-Sn-Cu, Al-Sn-Si, and Al-Sn-Bi alloys[1–55] have been extensively investigated in the substitution of materials traditionally used as structural components subjected to compressive, tractive and cyclic efforts and to frictional wear, such as sliding bearings. In the case of Al-Ni alloys, due to their microstructural features, consisting of two phases, an a-Al primary phase and an Al3Ni intermetallic, they have been highlighted as materials for use in harsh environments that require mechanical properties for high-temperature conditions such as a high Young’s modulus and a low coefficient of thermal expansion.[39] In addition, these alloys are potentially promising for
bimetallic applications in nanotechnology structures[35] and protective coatings.[40] Obviously, for these applications, more refined microstructures have been designed in binary alloys that have eutectic constituents, as observed in Al-Ni alloys.[41] Farahany et al.[42,43] reported that the addition of Bi to Al-based multicomponent alloys influenced the refinement of plate-like eutectic silicon in Al-7Si-0.4Mg alloys and changed the morphology of the primary Mg2Si particles in Al–20Mg2Si–2Cu metal matrix composites (MMCs) from plate to fibrous, improving the wear resistance of the investigated alloys. This improvement has been attributed to the solid lubricant function of the insoluble soft Bi phase and modification effects on Mg2Si particles.[43] More recently, Al-Bi alloys have been presented as viable options to replace and/or eliminate constituent layers of sliding bearings, thus reducing the weight of these components employed in various industry sectors, such as the aerospace and automo
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