Effect of NbB2 Nanoparticles on the Portevin-Le Chatelier Phenomenon in Al-Mg Alloys

Undergraduate #372
Discipline: Technology and Engineering
Subcategory: Materials Science

Michelle Marrero-García - University of Puerto Rico, Mayagüez Campus
Co-Author(s): Rafael Martínez, Javier Martínez, David Florián, and Oscar Marcelo Suárez, University of Puerto Rico, Mayagüez Campus, Mayagüez, PR

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This research focuses on the effects of the addition of niobium diboride (NbB2) nanoparticles on the Portevin-Le Chatelier (PLC) phenomenon, occurring primarily in aluminum alloys and some steels. It is evinced by serrations in the stress-strain curves, and occurs due to the precipitation from a supersaturated solid solution, as a consequence of dislocation movement. Hence, mechanical properties like strain rate, ultimate tensile strength, ductility and fracture toughness, among others, are affected. PLC, subsequently, snarls manufacturing of parts in transportation and aerospace industries, i.e. main users of aluminum-magnesium alloys. Pure aluminum pellets and a ballmilled composite, containing 90% Al – 10% NbB2 nanoparticles, were used to fabricate the specimens. Different amounts of the resulting composite were then added to a molten Al-Mg alloy. This was then cast into rods that were cold-rolled into wires with 1mm diameter. Three wire specimen sets were prepared: a control group, a solution-treated group, and a solution treated and aged group. The solution treatment consisted of annealing the samples and quenching them in ice water. Natural aging was used by storing the samples at room temperature for 168 hours before performing the tensile tests. Our results showed that the PLC occurred in the solution-treated, and the solution-treated and aged groups. As expected, the phenomenon was observable as the material entered the plastic region upon the tensile experiment. It was also noticeable that the phenomenon was affected by the addition of nanoparticles. However, further quantification of those effects using numerical analysis is required. To this purpose, noise signals are being filtered for proper modeling of the nanoparticles effect on the PLC phenomenon. Future studies hinge on the assessment of the amplitude and frequency of the peaks in the serrated plastic deformation section of the stress-strain curve.

Funder Acknowledgement(s): This material is based upon work supported by the National Science Foundation under Grant No. 1345156 (CREST Program).

Faculty Advisor: Oscar Marcelo Suárez, msuarez@ece.uprm.edu