Fabrication of New Composites Bearing High Wear Strength

1. Fabrication of New Composites Bearing High Wear Strength Oscar M. Suárez, University of Puerto Rico Mayaguez, DMR 0351449 • HRD 0833112 (CREST), DMR 0922994 (MRI) As part of the UPRM PREM project (DMR 0351449), a team led by the PI developed a new series of high strength, high wear resistance aluminum-based composites reinforced with hard diboride (AlB2) particles. The composite is intended for lunar exploration due to their high hardness-to-density ratio. As a result of the successful completion of the new composite development the research focused in the incorporation of harder aluminum compounds, Aluminum dodecaboride (AlB12) particles were selected to this purpose. The new composite displayed an even higher wear strength than the AlB2-containing material. Yet, the small reactivity previously observed between these particles and the liquid aluminum matrix upon processing could have caused a loss in hardness of the particle. For long wear processes that could cause earlier part failures. This eventuality was investigated using a recently acquired nanoindentation system (DMR 0922994). The figures on the right show the load vs. displacement curve resulting from a triangular indent (Bercovich tip) on an AlB12 particle embedded in the aluminum matrix and imaged using an atomic force microscope. The measured values of Young’s elastic modulus (E) and hardness (H) were 539.4 GPa, 48.9 GPa, respectively. Then they were contrasted with measurements on AlB12 single crystal available in the literature and it was discovered that there were no deterioration of those mechanical properties of the particle upon processing. As a consequence, the AlB12 containing composite is an even better alternative than the AlB2-reinforced one, where the nanoindenter measured E=224 GPa and H=17.5 GPa. The new material is being used in hybrid composites for device fabrication as part of a new Nanotechnology Center endeavor (HRD 0833112).