| Popis: |
The effects of thermal and thermomechanical processing, sample orientation, and load ratio on the room temperature fatigue crack growth and fracture behavior of a third-generation gamma titanium aluminide Ti-43.5Al-4Nb-1Mo-0.1B (TNM) were determined in this study. Bend bar specimens, excised from TNM in as-cast, cast + hot isostatic pressing, and forge + heat treat conditions in the longitudinal and transverse directions, were tested at room temperature in lab air. Load ratios in the range 0.1 – 0.9 were used in fatigue testing to determine their effects on the fatigue threshold, Paris law slope, and stress intensity at overload. Microscopy, fractography, and X-ray diffraction were used to understand the effects of process and testing variables on the fatigue crack path and morphology. The effects of microstructure length scales and microconstituents are discussed in relation to the properties measured. |
