Strengthening effects of TiC particles and microstructure refinement in in situ TiC-reinforced Ti matrix composites

- Beta transus temperatures of in situ TiC/Ti composites were measured and discussed.
- Various strengthening effects of TiC were modeled, main effects were clarified.
- Strengthening effects of microstructure refinement were measured and evaluated.
- Some models were suggested to evaluate the mechanical properties of TMCs.

TiC-reinforced Ti matrix composites of various TiC volume fractions were prepared via an in situ synthesis method. The microstructure of the composites was refined by thermo-mechanical processing yielding Widmanstätten and bimodal microstructures. The strengthening effects exerted by TiC reinforcement and microstructure refinement in the composite were evaluated via tensile tests at 873 K, and the strengthening mechanisms were investigated by transmission electron microscopy and mechanical models. The addition of carbon increased the beta transfus temperature of the composite significantly. The strengthening effect exerted by the solid solution carbon and dislocation hindering by the TiC particles played important roles in determining the strength of the prepared composites. In composites that featured Widmanstätten and bimodal microstructures with no precipitated silicides, the size of the α colonies was an important factor that determined the composite strength. In contrast, in composites wherein silicide precipitation had occur, the size of the α plates was a contributing factor owing to the dislocation hindering effect exerted by the silicides.

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