Partnership for Research and Education on Functional and Nanostructured Materials

1. Novel Application of Strain-Gradient Plasticity Theory to Reveal Nanomechanical Properties of AlB2 Particles Embedded in an Al MatrixOscar M. Suarez, University of Puerto Rico Mayaguez, DMR 0351449 Partnership for Research and Education on Functional and Nanostructured Materials Use of nanoindentation on hard AlB2 reinforcements of soft Al matrix caused strong dependence of results on the loading magnitude. In this highly heterogeneous material the diborides are pushed in into the matrix (upper figure), which confounds the measurements. To eliminate this artifact, strain-gradient plasticity (SGP) theory was applied so as to incorporate in the analysis of the results, the compliance of the aluminum matrix. By implementing the SGP theory this PREM team was able to resolve the suspected high anisotropy of AlB2 in terms of its mechanical properties. Assisted by electron backscattered diffraction (EBSD), the researchers were able to calculate the effect of AlB2 crystallographic directions with respect to the load on the measured nanomechanical properties (lower figure). This is opening a new direction in the proper analysis of nanoindentation data of highly heterogeneous materials. Scanning electron image of nanoindented AlB2 particle pushed in into the Al matrix J. E. Jakes, C. R. Frihart, J. F. Beecher, R. J. Moon, P. J. Resto, Z. H. Melgarejo, O. M. Suárez, H. Baumgart, A. A. Elmustafa, D. S. Stone, “Analysis of Nanoindentation Near Free Edges and Heterophase Interfaces,” J. Materials Research, 24 [3], (2009): pp. 1016-1031. P. J. Resto, Z. H. Melgarejo, D. S. Stone, O. M. Suárez, “Study of Particle-Matrix Interaction in Al/AlB2 Composite via Nanoindentation,” Materials Characterization, (2009) [submitted]. Dependence of J01/2 (H1/2/Eeff) on Φ for AlB2 particles.