Phase transformations in Ti3Al and Ti3Al + Mo aluminides

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Abstract
We have analyzed the phase relationships in two titanium aluminides containing 3.4 at. % Mo with different aluminum compositions. The alloys were first homogenized in the β field, then cooled continuously at different cooling rates from 80 °C/s to 0.1 °C/s. The continuous cooling transformation diagrams (CCT) show that phase transformations and resulting microstructures are highly dependent on cooling rate. The microstructure consists of ordered α2 (DO19), ordered β0 (B2), and athermal ω (hexagonal) phases. The “tweed microstructure” is observed. The evolution of microhardness was determined as well as the relative partitioning of Al and Mo in (α2', α2) and β0 phases as a function of cooling rate.