Dynamic high-strain-rate mechanical behavior of microstructurally biased two-phase TiB2+Al2O3 ceramics

The dynamic high-strain-rate behavior of two-phase TiB2+Al2O3 ceramics with biased microstructures was investigated in this study. The microstructural bias includes differences in phase (grain) size and phase distribution such that in one case a continuous (interconnected) TiB2 network surrounds the Al2O3 phase (qualitatively termed "T@A") and in another case the TiB2 and Al2O3 phases are interdispersed and uniformly intertwined with each other (qualitatively termed "TinA"). Quantitative microscopy was used to characterize the phase size and the integral curvature which is taken as a measure of TiB2 phase connectivity around Al2O3. Dynamic compression and tension (spall) properties were measured using plate impact experiments. The measurements used piezoelectric polyvinyldine fluoride stress gauges to obtain the loading profile and to determine the Hugoniot elastic limit. In addition, velocity interferometry system for any reflector interferometry was used to obtain the spall signal and the tensile dynamic strengths of the materials. Experimental results reveal that while the sigma(HEL) and the compressive strengths of TiB2+Al2O3 ceramics are dependent on the average grain (phase) size, the tensile (spall) strength scales with the TiB2-phase connectivity. This result suggests that the interconnected TiB2/Al2O3 microstructural morphology provides a stronger impediment to failure in tension compared with the morphology with simply interdispersed phases. (C) 2002 American Institute of Physics.