The influences of trace TiB and TiC on microstructure refinement and mechanical properties of in situ synthesized Ti matrix composite

Abstract

Ti–5Al–5Mo–5V–1Fe–1Cr Ti alloy and Ti–5Al–5Mo–5V–1Fe–1Cr Ti matrix composites containing different weight fractions of trace TiB and TiC are fabricated via in situ synthesis method. The as-cast ingots are subjected to thermo-mechanical processing and heat treatment. The Widmannstatten structure is obtained after the heat treatment. The microstructure length scales of the materials are identified. The identification indicates that 0.4wt.% TiB and 0.1wt.% TiC can reduce the average size of the β grains by more than 50%. Whereas the extent of the microstructure refinement gradually decreases while increasing the weight fraction of the trace reinforcements. The influences of weight fraction and morphology of the trace TiB and TiC on microstructure refinement are researched in this work. Moreover, the tensile properties of the heat-treated materials are examined. It is revealed that Hall–Petch mechanism plays an identically important role in improving the mechanical properties of the composites comparing with the load bearing and dispersion strengthening of the trace reinforcements.