Dynamic high-pressure properties of AlN ceramic as determined by flyer plate impact

The dynamic properties of hot-pressed aluminum nitride ceramics were determined in a series of plate impact experiments using longitudinal and transverse in-material manganin gauges. The Hugoniot curve for hot pressed specimens was determined in the range of 0–190 kbar with a value of 94±2 kbar for the Hugoniot elastic limit (HEL). Using both gauge orientations, the stress deviator in the specimens was determined as the difference between longitudinal and transverse stresses. It was found that the stress deviator remains relatively constant above the HEL, and is about 10% higher than the value at the HEL point. The inferred Hugoniot converges to the extrapolation of the hydrostat. Since the convergence is not due to loss of strength, it may be due to a phase change in the AlN from low-pressure (wurtzite) structure to high-pressure (rocksalt) structure.