The Effects of Residual Stress Distributions on Indentation-induced Microcracking in B_4C-TiB_2 Eutectic Ceramic Composites

摘要

The boron carbide (B_4C) titanium diboride (TiB_2) ceramic eutectic is being investigated for armorand tribological applications. Electron diffraction shows [1 120] TiB_2//[2131] B_4C// growth direction, (0001) TiB_2//(1210) B_4C is parallel to the interface plane, and transmission electron microscopy (TEM) imaging reveals no interface phase. Thermal residual stress distributions are calculated via finite element modeling of an experimental eutectic microstructure. The B_4C matrix is found to be about 400 Mpa in compression, and the TiB2 lamellae approximately 1.3 Gpa in tension. Stress and strain energy concentrations are found at the tips of TiB_2 lamellae. TEM of deformed materials correlates well with the finite element calculations, showing preferential fracture in areas of stress concentration. Interfacial delamination and crack deflection are also observed in deformed materials.