The presence of deformation twins was documented in boron carbide reinforcement particles within a nanostructured Al 5083/B4C metal matrix composite. High-resolution transmission electron microscopy analysis suggested that these were (00•1) twins. This work considered the mechanisms responsible for their formation based upon crystallographic analysis and mechanical loading conditions. Specifically, it was proposed that there were two potential models that could be used to describe twin formation in boron carbide particles. The structural models involved slip in the 1/3[11•0](01•0) or 1/3[01•0](01•0) 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 indicated that local high stress intensity and the presence of a high shear force around the boron carbide particles were two factors that contributed to twin formation.

Deformation Twinning in Boron Carbide Particles within Nanostructured Al 5083/B4C Metal Matrix Composites. Y.Li, Y.H.Zhao, W.Liu, Z.H.Zhang, R.G.Vogt, E.J.Lavernia, J.M.Schoenung: Philosophical Magazine, 2010, 90[6], 783-92