Microstructural characteristics and mechanical properties of in situ synthesized (TiB + TiC)/TC18 composites

Trace reinforcements can significantly refine microstructure and improve mechanical performance of composite. In this work, the in situ synthesized Ti–5Al–5Mo–5V–1Fe–1Cr titanium matrix composite containing trace TiB and TiC is fabricated. The microstructural characteristics and tensile properties of the heat-treated materials are investigated, with particular emphasis on researching the spheroidization of α phase and the effects of trace reinforcements. It is revealed that it presents the division of α grain during spheroidization process. The separated α phase, near equiaxed α phase and short-rod α phase tend to be spheroidized during the processing of diffusion. The trace reinforcements can accelerate the spheroidization of α by accelerating the extent of diffusion and then the microstructural homogeneity is promoted. The composite manifests excellent comprehensive mechanical properties due to the microstructural improvement and the effect of the trace reinforcements.

► Little information is available so far on Ti–5Al–5Mo–5V–1Fe–1Cr titanium matrix composite.
► The spheroidization of α in the composite during heat treatment has not been researched.
► Trace reinforcements can accelerate the spheroidization of α phase and promote microstructural homogeneity of the composite.
► The composite with spheroidization structure presents excellent comprehensive mechanical properties. The tensile properties of the composite are superior to those of the alloy.
► The promotion of the microstructural homogeneity is a major reason for the improvement of the mechanical properties of the composite, so are the effects of trace reinforcements.