Degradation of TiB_2 ceramics in liquid aluminum

摘要

Infiltration of liquid aluminum in three TiB_2 materials with significantly different microstructures at 1000 deg C has been studied. The results show large differences in resistance towards aluminum penetration. A TiB_2 material containing transition metal sintering aid, displayed a low resistance towards penetration of liquid aluminum along grain boundaries. Grain boundary penetration was also observed in a second material containing an oxycarbide secondary phase TiC_(1-x)O_x, while Al infiltration could not be detected after 100 h, in a third material with apparently no secondary phases. The flexural strength, hardness and stiffness of the exposed material showing the lowest resistance towards penetration of aluminum, decreased due to penetration along grain boundaries, and the fracture mode changed from transgranular to intergranular. The experimental observations were analyzed using a two-dimensional finite element model, reproducing the observed reduction in the stiffness due to aluminum infiltration.