Dynamic mechanical properties of microstructurally-biased two-phase TiB_2+Al_2O_3 ceramics

摘要

The dynamic properties of two-phase TiB_2+Al_2O_3 (30:70 nominal ratio) ceramics with biased microstructures were investigated in this study. The microstructural bias includes differences in phase (grain) size and phase distribution such that in one case a continuous (interconnected) TiB_2 network surrounds the Al_2O_3 phase (qualitatively termed 'T@A'), and in another case the TiB_2 and Al_2O_3 phases are interdispersed and uniformly inter-twined with each other (qualitatively termed TinA'). Quantitative microscopy was performed to characterize the phase size and integral curvature as a measure of TiB_2 phase connectivity around Al_2O_3. Dynamic compression and tension (spall) properties were measured using plate-impact gas-gun and Split-Hopkinson Pressure Bar experiments. The measurements used piezoelectric PVDF stress gauges to obtain the loading profile and determine the Hugoniot Elastic Limit, and VISAR interferometry to obtain the spall signal and determine tensile properties. Micromechanical modeling based on a cohesive surface formulation that explicitly describes arbitrary microstructures and arbitrary fracture patterns, was used to study the deformation and damage sub-structure evolution during impact loading. The results of the quantitative microstructural characterization correlated with measured dynamic properties obtained from impact experiments, coupled with results of numerical simulations will be discussed.