Microstructural and load hold effects on small fatigue crack growth in α plus β dual phase Ti alloys

Microstructurally small crack growth was monitored in Ti-6Al-4V and Ti-6Al-2Sn-4Zr-2Mo with equiaxed and bimodal microstructures. The influence of the microstructure was assessed to obtain an improved understanding of the lifetime variability observed in Ti alloys. Primary alpha grains, basal plane cracking and misalignment across boundaries were identified as key features for high crack growth rates. The origin of life debits encountered under dwell-fatigue loadings was also investigated through crack growth monitoring with the introduction of load holds at peaks stress. Dwell periods were found to induce a substantial small crack acceleration.

Automated summary

This study monitored the microstructurally small crack growth in Ti-6Al-4V and Ti-6Al-2Sn-4Zr-2Mo with equiaxed and bimodal microstructures. The influence of microstructure on the lifetime variability observed in Ti alloys was evaluated, and primary alpha grains, basal plane cracking, and misalignment across boundaries were identified as key features for high crack growth rates. Dwell periods were found to induce significant small crack acceleration.