The influence of loading cycle and environment on fatigue crack propagation in Ti6246 alloy

Fatigue crack growth tests on Ti-6Al-2Sn-4Zr-6Mo(Ti6246) alloy were carried out at 773K with either cyclic and dwell waveforms in air, an intermediate vacuum and high vacuum. Results for the DEN (Double Edge Notch) specimens showed that the fatigue crack growth rate with the dwell waveform was the h ighest among the various waveforms presently studied. Particularly at low s tress intensity factor range (DeltaK), the fatigue crack growth rate was co nsiderably affected by different waveforms. The difference in fatigue crack growth rates between cyclic and dwell waveforms was, however, reduced at i ntermediate and high DeltaK regions. The effect of environment on fatigue c rack growth rate in Ti6246 alloy was also significant at 773K. The highest resistance to fatigue crack growth was observed in a high vacuum, followed by air and an intermediate vacuum. The highest fatigue crack growth rate wa s obtained in an intermediate vacuum, but there was only slight variation o n the fatigue crack growth rates in between air and an intermediate vacuum.