Deformation twinning in boron carbide particles within nanostructured Al 5083/B4C metal matrix composites

The presence of deformation twins is documented in boron carbide reinforcement particles within a nanostructured Al 5083/B4C metal matrix composite. High resolution transmission electron microscopy analysis suggests that these are (0001) twins. This work discusses the mechanisms responsible for their formation based on crystallographic analysis and mechanical loading conditions. Specifically, we propose that there are two potential models that can be used to describe twin formation in boron carbide particles. The structural models involve slip in the 1/3[(1) over bar 100] (01 (1) over bar0) or 1/ 3[01 (1) over bar0] (01 (1) over bar0) planes of C-C-C chains and the appropriate reconfiguration of B-C bonds. Analysis of the loading conditions experienced by the boron carbide particles indicates that local high stress intensity and the presence of a high shear force around the boron carbide particles are two factors that contribute to twin formation.