Microstructure and fabrication of hybrid in situ titanium matrix composites

The feasibility of fabrication in situ TiB and TiC hybrid titanium matrix composites based on a Ti-B₄C-C system was analyzed in theory and chemical reactions among the blended powders of Ti, B₄C and C powders during the heating process was studied by differential scanning calorimetry (DSC). The results of DSC show that drastic exothermal reactions take place during the course of heating, which indicates that some new phases are formed. X-ray diffraction (XRD) patterns of the as-sintered composites reveal that TiB and TiC would be formed in the as-sintered composites and the peak intensity of TiC increases with increasing amount of graphite powder, showing that both the reactions of Ti-B₄C and Ti-C systems have taken place completely within the range of 940~1150℃. OM and SEM results show that rodlike TiB whiskers and equiaxed TiC particulates distribute uniformly in titanium matrix. It is suggested that in situ TiB whisker and TiC particulate hybrid reinforced titanium matrix composites can be prepared by hot pressing of a Ti-B₄C-C system.