Influence of constitutional undercooling on grain refinement in titanium aluminide alloys

In this present work, the influence of constitutional undercooling on the grain size of titanium aluminide alloys and the dependence on boron content have been investigated. By means of the TTTIAL1 thermodynamic database of the Thermo-Calc programme, the values of the growth restriction factor for a series of alloys have been calculated. It can be shown that grain size decreases with increasing growth restriction factor. A comparison of calculated and published experimental results shows that the constitutional undercooling significantly influences the grain size in titanium aluminide alloys, but most likely, it is not the unique mechanism of grain refinement alone, in so far as not all of the experimental results may be explained by the influence of constitutional undercooling.