Discipline: Technology and Engineering
Christian Vázquez Rivera - University of Puerto Rico - Mayaguez
Co-Author(s): Andres Calle and O. M. Suárez, University of Puerto Rico, Mayagüez
Aluminum is a high-demand material for welding applications in the automotive and aerospace industries among others. Aluminum welds satisfy requirements of strong joints of parts adding minimal weight as demanded in many structures. However, the performance of these welds at high temperatures is unsatisfactory showing crack sensitivity. The reinforcement of aluminum fillers with niobium diboride (NbB2) nanoparticles can improve the welding quality and increase its high-temperature service capacity. Nonetheless, prior studies on reinforcing aluminum matrices with nanoparticles revealed lack of homogenous distribution of the added particles affecting the metal performance. To overcome this limitation, we used stir casting during the manufacturing process of novel aluminum fillers reinforced with NbB2 nanoparticles. The completion of a central composite design experiment allowed optimizing the manufacturing process by varying the stirring speed and stirring time to optimize the fillers quality. In this study, as in many industries, we employed the tungsten inert gas (TIG) welding method. Advantages of TIG method include an inert gas constantly providing a clean environment upon the process. The NbB2 nanoparticles were obtained by high energy ball mill fragmentation and mechanically alloyed to form Al/NbB2 nanocomposite pellets that were incorporated into the melt. Filler wires were prepared with different amounts of nanoparticles and an Al – 5 wt.% Mg binary alloy. Filler rods of 2.4 mm in diameter were obtained via rolling. The analysis of the results showed that the fillers hardness can be increased by 7% with the addition of 2%wt of nanoparticles stirring the mix at 750 revolutions per minute for 12 seconds. To assess the factors affecting the ultimate tensile strength, we employed a full factorial design by fixing the amount of nanoparticles at 1%wt and varying levels of the same casting parameters studied before. The experiment yielded similar results, suggesting that better fillers can be obtained by stirring the molten alloy at high speed for a short period of time. Porosity analysis also agreed with the results of the experimental design, entailing the achievement of a better weld quality. Ongoing and upcoming work includes the study of thermal expansion coefficient of the reinforced filler along with an analysis of the melting behavior upon welding on a commonly used base material.
Funder Acknowledgement(s): This material is based in part upon work supported by the National Science Foundation Grant No 1345156 (CREST Program).
Faculty Advisor: Oscar Marcelo Suarez, firstname.lastname@example.org
Role: Initially my effort was put on the review of literature required for the understanding of aluminum welding and obtain the necessary knowledge for the completion of experiments, this include the development of welding skills for the fabrication of our samples. Then, in the next three experiments conducted, I contribute in the preparation of materials including the NbB2 nanoparticles via planetary ball mill, the fabrication of fillers via casting and cold rolling. Finally, for fillers’ quality assessment, I carried out porosity and hardness analysis through micrographs obtained at the laboratory.