Effect of Ti content and sintering temperature on the microstructures and mechanical properties of TiB reinforced titanium composites synthesized by SPS process

Titanium matrix composites reinforced with TiB whiskers have been synthesized using the spark plasma sintering method at temperatures between 950-1250 degrees C. The influences of the Ti content of the initial mixtures and sintering temperature on the microstructure and mechanical properties of the TiB-Ti composites are investigated. The results indicate that the average size of the TiB whiskers increases significantly with an increase in Ti content of the initial mixtures. However, the TiB whiskers in the composites synthesized from the mixtures containing low content of Ti powders have a high tendency to agglomerate. Both bending strength and fracture toughness of the TiB-Ti composites increases with increasing Ti content of the initial mixtures. But bending strength increases slightly with increasing sintering temperature because of the simultaneous increase in the relative density of the composite and the average grain size of the TiB reinforcement. The results also suggest that hybrid-fracture characteristics appear in the fracture surface of the TiB-Ti composites synthesized in situ, which includes pull-out of the TiB reinforcement and the quasi-cleavage of the Ti matrix. Quasi-cleavage of the Ti matrix are the dominant fracture modes in the composites, and the volume fractions of pull-out of the TiB whiskers are relatively low. (C) 2012 Elsevier B.V. All rights reserved.