Study of Thermo-Mechanical Properties of an Al-Zn Matrix Reinforced with Dodecaboride Particles

Undergraduate #369
Discipline: Technology and Engineering
Subcategory: Materials Science

Marivic Hernández - University of Puerto Rico - Mayaguez Campus
Co-Author(s): José Luis Colón, Sujeily Soto, and Oscar Marcelo Suárez, University of Puerto Rico – Mayagüez

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Aluminum-zinc alloys have been widely used in automotive and aerospace applications due their small weight-to-strength ratio. In particular, the study of the behavior at high temperatures of these composites has been mandatory. Previous studies have shown that adding hard boride particles to an aluminum matrix can enhance the resulting composite mechanical strength. This research, specifically, studied the effect of AlB12 particles in an Al-Zn matrix at high temperatures. These composites were characterized using thermo-mechanical analysis (TMA), Rockwell hardness and optical microscopy. The composite samples were homogeneized at 500ºC and then quenched in ice water. Subsequently the specimens were studied at 125ºC, 160ºC and 200ºC in the TMA to simulate an aging treatment. As expected, the resulting Rockwell hardness of the composite specimens increased for higher concentrations of AlB12 particles. However, such increment was not uniform for all samples at higher temperatures, which suggests an interaction between the dodecaboride particles and zinc. This was further corroborated by the TMA experiments, where samples with higher zinc levels containing AlB12 particles underwent higher deformations at higher temperatures. After the TMA experimentation, optical microscopy revealed the precipitation of zinc near or at the aluminum grain boundaries. This led us to discard the potential effect of fine precipitation due to aging in the composites.

Funder Acknowledgement(s): This study was based upon work supported by the National Science Foundation under Grant No. HRD 1345156 (CREST Phase II).

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