ATOM-PROBE DETERMINATION OF INTERSTITIAL ELEMENT CONCENTRATION IN 2-PHASE AND SINGLE-PHASE TIAL-BASED ALLOYS

Interstitial elements (O,C,N) seem to have a key role with respect to mechanical properties of TiAl-based alloys. This paper presents an ato m-probe study of the distribution of interstitial elements in the alph a2 and gamma phases of two-phase TiAl alloys. These elements are found to preferentially segregate in the alpha2 phase. This effect is parti cularly important for oxygen. Measurements of oxygen concentration in the gamma phase of two-phase and of single-phase alloys were performed . This allows the maximum solubility of oxygen in the gamma phase to b e determined. The result shows that the poor low-temperature ductility of single-phase TiAl alloys cannot be simply due to the presence of o xygen in the gamma phase.