Abstract
The study of Al based ultrafine-grained (UFG) composites is prompted by the objective to develop ultrahigh strength (>1000 MPa), low density materials that also posses attractive high strain rate behavior. In this study, UFG Al/B4C composites with a B4C reinforcement size of ~1 m and ~50 nm, respectively, were produced via cryomilling followed by consolidating via HIP and extrusion. The results showed that the mechanical milling process led to a homogeneous distribution of the micro- and nano-particles in the matrix and the matrix had an average grain size of ~300 nm after consolidation. HRTEM revealed a clean Al/B4C interface and no detrimental interfacial phase or defects such as voids were observed. The mechanical behavior of the UFG composites were studied and the strengthening mechanisms were discussed in the frame work of load transfer, Hall-Petch strengthening, geometry necessary dislocation strengthening and dispersion strengthening.