Enhancement of Mechanical Strength in Hot-Pressed TiB sub 2 Composites by the Addition of Fe and Ni

摘要

Improvement in the fracture strength of TiB sub 2 composites through the addition of Fe and Ni is reported. Beam specimens containing up to 20 wt % of the metal component were fabricated by hot pressing above the eutectic temperature. Four point bending results indicated that the observed enhancement in strength was proportional to the vol % of the metal present. The results also revealed that TiB sub 2 --Ni composites have slightly better strength than TiB sub 2 --Fe samples at elevated temperatures, and that their strengths were consistently about twice that of pure TiB sub 2 . They also did not exhibit any serious degradation in strength up to 700 exp 0 C. The fracture behavior was characterized using optical and scanning electron microscopy. The strengthening appears to be related to the presence of a metallic grain boundary phase between TiB sub 2 particles. The results further suggested that the formation of a special eutectic-like grain microstructure could render additional strengthening. (ERA citation 04:023995)