In-situ measurement of continuous cooling beta ->alpha transformation behavior of CP-Ti

Abstract

The beta --> alpha transformation kinetics of CP-Ti during continuous cooling was measured using a fully computer-controlled resistivity-temperature real-time measurement apparatus. Unlike the pure Ti case, the massive transformation occurs at medium cooling rates, about 90 degreesC/s to 600 degreesC/s. Its start temperature is estimated to be about 890 degreesC, which is close to the To temperature. The reason for the appearance of massive transformation in CP-Ti is because CP-Ti contains a significant amount of Fe as an impurity, which leads to the T-0(beta --> alpha) vs composition curve being parallel to the composition axis due to its retrograde solubility. The martensitic transformation starts to occur at a cooling rate of about 500 degreesC/s, which is much slower than that (about 3000 degreesC/s) reported in a pure Ti case. This retardation effect of martensitic transformation is also believed to arise from the presence of Fe in CP-Ti, which is a strong beta stabilizer.