Effect of α phase morphology on fatigue crack growth behavior of Ti-5Al-5Mo-5V-1Cr-1Fe alloy
(1. School of Materials Science and Engineering, Central South University, Changsha 410083, China;
2. Advanced Research Center, Central South University, Changsha 410083, China;
3. State Key Laboratory of Powder Metallurgy, Central South University, Changsha 410083, China)
2. Advanced Research Center, Central South University, Changsha 410083, China;
3. State Key Laboratory of Powder Metallurgy, Central South University, Changsha 410083, China)
Abstract: Taking a Ti-5Al-5Mo-5V-1Cr-1Fe alloy as exemplary case, the fatigue crack growth sensitivity and fracture features with various tailored α phase morphologies were thoroughly investigated using fatigue crack growth rate (FCGR) test, optical microscopy (OM) and scanning electron microscopy (SEM). The tailored microstructures by heat treatments include the fine and coarse secondary α phase, as well as the widmanstatten and basket weave features. The sample with coarse secondary α phase exhibits better comprehensive properties of good crack propagation resistance (with long Paris regime ranging from 15 to 60 MPa·m1/2), high yield strength (1113 MPa) and ultimate strength (1150 MPa), and good elongation (11.6%). The good crack propagation resistance can be attributed to crack deflection, long secondary crack, and tortuous crack path induced by coarse secondary α phase.
Key words: Ti-5Al-5Mo-5V-1Cr-1Fe alloy; α phase; fatigue crack growth; fracture feature