Optimization of thermomechanical treatments of titanium alloys (in view of improving mechanical properties) requires a better knowledge 4 transformation mechanisms. Fr and CCT (continuous cooling transformation) diagrams were drawn for three alloys after being put into solution in the #beta# (T#beta#+ 30 deg C) domain thanks to the continuous measurement of the resistivity during heat treatment, dilatometry and metallography. Thus, tour distinct isotherm transformation domains are shown. The analogies between the alloys are more marked at high temperature than at low temperature. In anisothermal conditions, the transformation domains crossed during cooling correspond in reality to he ones defined by the C-curves of the Fr diagrams. Comparison of he various diagrams clearly shows the influence of the chemical composition on the precipitation kinetics and on the nature of the phases appearing at low temperature.
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