Analysis of the Strength Property for TiC-Mo Composites at High Temperature

TiC-21 mol% Mo solid solution (delta-phase) and TiC-99 mol% Mo solid solution (beta-phase), and TiC-(80 similar to 90) mol% Mo hypo-eutectic composite were deformed by compression in a temperature range from room to 2300 K and in a strain rate range from 4.9 x 10(-5) to 6.9 x 10(-3)/s. The deformation behaviors of the composites were analyzed from the strengths of the delta- and beta-phases. It was found that the high strength of the eutectic composite is due primarily to solution hardening of TiC by Mo, and that the delta-phase undergoes an appreciable plastic deformation at and above 1420 K even at 0.2% plastic strain of the composite. The yield strength of the three kinds of phase up to 1420 K is quantitatively explained by the rule of mixture, where internal stresses introduced by plastic deformation are taken into account. Above 1420 K, however, the calculated yield strength was considerably larger than the measured strength. The yield stress of beta-phase was much larger than that of pure TiC. A good linear relationship was held between the yield stress and the plastic strain rate in a double-logarithmic plot. The deformation behavior in delta-phase was different among the three temperature ranges tested, i.e., low, intermediate and high. At an intermediate temperature, no yield drop occurred, and from the beginning the work hardening level was high. At the tested temperature, a good linear relationship was held in the double logarithmic plot of the yield stress against the plastic strain rate. The strain rate dependence of the yield stress was very weak up to 1273 K in the hypo-eutectic composite, but it became stronger as the temperature rose.