The effect of an interstitial element, carbon, on the phase equilibria between a and g phases in Ti-Al-Nb ternary system was examined, particularly paying attention to the phase stability between the two phases, by using two series of alloys Ti-44Al-7Nb and Ti-46.5Al-7Nb without and with carbon of 0.5 at.%. The alloys were homogenized in the a single phase region, and then cooled to the temperatures near the a/a+g transus and held there, followed by water quench. From the microstructure observations and composition analysis, the a transus temperature increases by 5 K at 46.5Al and 15 K at 44Al by carbon in solution. The Al content in g phase in equilibrium with a phase in the alloy with carbon becomes lower than that of the alloy without carbon with decrease in temperature. Carbon atoms tend to be dissolved in the g phase more than in the a phase as temperature decreases. These results suggest that the expansion of the g single phase region toward lower Al concentration is attributed to the increase in phase stability of the g phase against a phase by carbon in solution, and this is responsible for the increase in the a transus temperature
各種検索
サポート
ヘルプ