Entwicklung und Charakterisierung von hoch Niob-haltigen Gamma-Titanaluminid Legierungen
Research output: Thesis › Doctoral Thesis
Intermetallic -TiAl based alloys exhibit increasing technical importance for high-temperature applications in automotive and aerospace industries. Their advantage is mainly seen in low density, combined with high specific yield strength and stiffness, good creep properties up to high temperatures as well as good oxidation resistance. 3rd generation titanium aluminides are high Nb bearing alloys and an example of complex multi-phase materials. The present work combines the determination of transition temperatures by heat-treatments followed by a metallographic examination of the microstructure and by means of differential scanning calorimetry (DSC). Complementarily, appearing phases and transition temperatures were predicted by thermodynamic calculations employing a commercially available TiAl database. In order to reach better agreement of the prediction of transition temperatures the database was modified by using the experimental determined data. Deformation test were conducted on a deformation dilatometer and the influence of temperature, deformation rate and strain on the flow stress of an industrial-scale alloy (TNB-V5) was investigated. With this knowledge an industrial-scale forging process was realized. Additionally a new alloy (TNM-B1) was designed and characterized in order to permit a near conventional forging process. The microstructure of deformed parts was characterized by means of electron microscopy, electron back-scattered diffraction and X-ray diffraction.