Florián Algarín, David J.
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Publication Restricted Study of wire fabrication of aluminum treated with diboride particles(2014) Florián Algarín, David J.; Suárez, O. Marcelo; College of Engineering; Quintero Aguiló, Pedro O.; Valentín Rullán, Ricky; Department of Mechanical Engineering; Hernández Rivera, Samuel P.The present thesis focuses on the fabrication of aluminum wires by adding XB2 nanoparticles into an aluminum matrix, where X is a transition metal: Nb, Mg and Zr. The incorporation of aluminum in the XB2 particles is normally a complex process due to lack of enough affinity between the components. Liquid aluminum has a high surface tension, combined with the unavoidable oxide layer that is formed externally on the diboride prevents proper contact between the particle and liquid aluminum at the fabrication temperatures. An alternative process is then needed for proper inoculation of Al with the diborides. Diboride nanoparticles were obtained by fragmentation in a high energy ball mill and then mechanically alloyed with pure aluminum powder to form nanocomposite pellets. High energy ball milling was selected as the key process to achieve appropriate mixing and homogenization between components. The XB2/Al pellets were then sintered in a reduced vacuum atmosphere in order to increase the homogenization of the pellets and enhance the strength of diboride/ aluminum interface. The pellets of XB2/Al were added into the molten aluminum and mixed. The treated melt was then poured into a cylindrical mold to produce cylindrical ingots, which were subsequently cold-rolled to obtain wires with 1 mm diameter with a cross area reduction of 91%. The wire specimens were mechanically characterized and their electrical resistivity was measured and compared with pure aluminum. The results obtained in this thesis clearly demonstrated the feasibility of improving the mechanical properties of the material without significantly affecting its electrical resistivity of the wires.Publication Open Access Strengthening of aluminum wires treated with A206/Alumina nanocomposites(MDPI, 2018-03-10) Marrero Rosa, Raúl; Li, Xiaochun; Choi, Hongseok; Suárez, O. Marcelo; Florián Algarín, David J.; College of Engineering; Department of Materials Science and EngineeringThis study sought to characterize aluminum nanocomposite wires that were fabricated through a cold-rolling process, having potential applications in TIG (tungsten inert gas) welding of aluminum. A206 (Al-4.5Cu-0.25Mg) master nanocomposites with 5 wt % γAl2O3 nanoparticles were first manufactured through a hybrid process combining semi-solid mixing and ultrasonic processing. A206/1 wt % γAl2O3 nanocomposites were fabricated by diluting the prepared master nanocomposites with a monolithic A206 alloy, which was then added to a pure aluminum melt. The fabricated Al–γAl2O3 nanocomposite billet was cold-rolled to produce an Al nanocomposite wire with a 1 mm diameter and a transverse area reduction of 96%. Containing different levels of nanocomposites, the fabricated samples were mechanically and electrically characterized. The results demonstrate a significantly higher strength of the aluminum wires with the nanocomposite addition. Further, the addition of alumina nanoparticles affected the wires’ electrical condutivity compared with that of pure aluminum and aluminum–copper alloys. The overall properties of the new material demonstrate that these wires could be an appealing alternative for fillers intended for aluminum welding,Publication Restricted Study of portevin-le chatelier phenomenon in Al-Mg alloys treated with nanoparticles(2019-12-09) Florián Algarín, David J.; Suárez, O. Marcelo; College of Engineering; Suárez, Luis E.; López Rodríguez, Ricardo R.; Acosta Costa, Felipe J.; Department of Civil Engineering; Cancelos Mancini, SilvinaThis dissertation focuses on the study of the Portevin-Le Chatelier (PLC) phenomenon in Al-Mg (aluminum-magnesium) alloys. First, the research centered on the development of methodologies for the effective insertion of nanoparticles in an aluminum matrix. In these studies, Al2O3 and MoB2 nanoparticles were incorporated in pure aluminum and A206 alloy matrix to evaluate the effect of these reinforcements on the mechanical and electrical properties of the composites and the effectiveness of the methods developed. Second, the research studied the PLC phenomenon when Al/NbB2 nanocomposite pellets prepared via high-energy ball milling, and A206 - 1 wt.% Al2O3 nanocomposites are present in a magnesium-supersaturated Al matrix. The nanocomposites were added into a molten Al-Mg alloy to produce cylindrical ingots. These were subsequently cold-rolled to obtain wires with 1 mm diameter to produce specimens for standard tensile tests. Prior to the tensile test, the samples underwent a 30 minute solution treatment at 300 C, followed by ice-water quenching. As expected, the results corroborated that the phenomenon was observable only in the specimens bearing the solution treatment. The phenomenon was observable as the material entered the plastic region of the stress-strain curves. The results obtained in this thesis clearly demonstrated what the addition of the Al2O3, and NbB2 nanoparticles attenuated the serrated signal amplitude of the PLC phenomenon.