Effect of MgO·Al2O3·SiO2 glass-ceramic as sintering aid on properties of alumina armors

Liquid-phase sintering is advantageous compared to solid-state sintering in manufacturing ceramic composites including lightweight armors. The crystalline phases formed from the liquid phase affect the mechanical properties of the material, and thus, to the best of our knowledge, their effect on the ballistic behavior need to be understood. In this paper, the correlation between mechanical properties and ballistic performance of non-stoichiometric cordierite-based glass-ceramic/alumina composites arrays with 99.8% purity was evaluated. The precursor alumina had average particle sizes of 0.5 and 1.7 μm, and the added glass-ceramic contents were 7 and 14 vol%. Cold-pressed samples were sintered under conditions of maximum densification. The behavior of each composition was compared with that of pure alumina with respect to sintering, mechanical properties, and ballistic performance evaluated by depth of penetration (DOP). For a single precursor alumina, decreases in ballistic resistance were observed with increases in the content of glass-ceramic due to the reduction in mechanical properties, specially hardness and Young's modulus (E). The overall analysis of the data indicated that ballistic behavior of alumina is more complex, and the toughness (KIC) and hardness (HK) can be regarded as predictive properties for determining alumina ballistic performance in DOP test. It is demonstrated that glass-ceramic addition lead to lower sintering time and temperature, from 1670 °C for 5 h to 1570 °C for 0.5 h, and these compositions have the similar areal density of pure alumina regarding ballistic performance, with less than 4% difference between 1.7 μm pure alumina and the composition with 7 vol% glass-ceramic precursor addition.