Fatigue Crack Growth of Ti-48Al-2Mn-2Nb Intermetallics by Centrifugal Spray Deposition

Abstract

Based upon understanding the effects of CSD and HIP processing on the mechanical properties and microstructure of the TiAl alloy, three point bending fatigue tests were carried out under load control at room temperature, and fatigue crack growth process and fatigue thresholds of the Ti-48Al-2Mn-2Nb alloys by CSD and HIP were investigated. The results show that the mean stress inducing fatigue crack initiation from notch tip and the stress intensity factor for the CSD TiAl samples are 346 MPa and 9.60 MPa•m 1/2 , respectively, while 307 MPa and 8.67 MPa•m 1/2 for the HIP TiAl samples, correspondingly. The CSD TiAl samples show better fatigue crack growth resistance and higher fatigue threshold than that of the HIP TiAl samples. It indicates clearly that the lamellar structure has a better resistance to fatigue crack growth than that of duplex structure. The fatigue crack growth process and mechanism for the CSD and the HIP samples are discussed.