Ti-4.5Al-4Cr-0.5Fe-0.2C is solution-hardened effectively in the temperature range up to 500degreesC due to its ultra high carbon content. On the other hand, the solution hardening effect is considerably reduced at temperatures higher than 500degreesC because the carbon is interstitial, leading to extra low flow stress similar to commercially pure titanium at 850degreesC. In an alloy system of Ti-4.5Al-4Cr-0.5Fe-C, we have examined the microstructural changes with increasing carbon content to find out if TiC and beta phase could metastably exist even below a peritectoid temperature with C no less than 0.15%. Metastably existing TiC basically transforms into alpha phase during heating at high temperatures below the peritectoid temperature that was finally determined to be 970degreesC. Even if a small amount of TiC was retained for Ti-4.5Al-4Cr-0.5Fe-02C, its fatigue strength was also comparable to Ti-6Al-4V.