Abstract
Microstructural changes in Ti-5.6Al-4.8Sn-2.0Zr-1Mo-0.34Si-0.7Nd containing different amounts of carbon during solution treatment in the upper (α + β) field have been investigated. It was observed that the (α + β)/β transus temperature increases rapidly in the carbon range 0-0.32 wt-% and exhibits a maximum at a content of 0.32 wt-%, while the α/(α + β) transus temperature increases in a much less pronounced manner. For solution treatment in the high temperature (α + β) phase field, carbon addition in the range 0-0.23 wt-% retards the change in volume fraction of the primary α phase with temperature. This makes it easier to adjust the volume fraction of the primary α phase through control of heat treatment temperature. Regression equations to predict the variation of volume fraction of primary α phase were obtained by multiple regression analysis. The experimental results are discussed in terms of phase composition analysis and the Ti-8Al-C phase diagram.
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