Determination of the (α + β)/β-transition temperature in the quasi-binary system Ti5Al2.5Fe - H as a function of its hydrogen content

Near net shape components of titanium and titanium alloys produced by precision casting often show poor mechanical properties, especially a poor fatigue strength because of their coarse microstructure caused by the high process temperature. As hydrogen can be dissolved reversibly in titanium and titanium alloys and lowers the (α +β)/β-transition temperature, a thermochemical treatment can provide a reduction in grain size and hence improve the mechanical properties. The knowledge of the exact transition temperature depending on the hydrogen content will allow the development of such a thermochemical treatment. In the present study, the (α + β)/β-transition temperature of the biocompatible alloy TiAl5Fe2.5 was determined as a function of the hydrogen content by isothermal metal-gas-reaction measurements.