High cycle fatigue properties of Ti-48Al-2Cr-2Nb alloy additively manufactured via twin-wire directed energy deposition-arc

Recently, additive manufacturing for titanium aluminide has received sustained attention. Considering the extensive applications on low pressure turbine blades in aerospace field, dynamic mechanical properties of titanium aluminide, especially the fatigue properties, are of great importance. In present work, fatigue test at ambient temperature was conducted for the first time on twin-wire directed energy deposition-arc (TW-DED-arc) fabricated Ti-48Al-2Cr-2Nb alloy with equiaxed lamellar colonies. More detailed researches on fatigue fracture characteristics and deformation modes are also investigated. The experiment results indicate that TW-DED-arc fabricated Ti-48Al-2Cr-2Nb alloy exhibits flat S–N behavior with a good resistance to fatigue. Fatigue life fluctuates widely at same stress level, but such fluctuations gradually weaken as stress decreases. Furthermore, γ/α₂ interface and lamellar colony boundary as well as special microstructures of as-fabricated Ti-48Al-2Cr-2Nb alloy are weak areas during fatigue process, which easily become crack nucleation sites. As stress level decreases, deformation mode of as-fabricated Ti-48Al-2Cr-2Nb alloy translates from twinning and dislocation slip to predominantly dislocation slip. In general, these findings provide an important reference for engineering applications of titanium aluminide.