Geometrical Scale-Sensitive Fatigue Properties of Ti–6.5Al–3.5Mo–1.5Zr–0.3Si Alloys With α/β Lamellar Microstructures

Fatigue properties of the Ti–6.5Al–3.5Mo–1.5Zr–0.3Si alloy sheets containing different numbers of α/β Widmanstätten colonies in the thickness direction of the sheets were investigated by tension–tension fatigue testing. It is found that fatigue properties of the Ti alloy either in low- or high-stress amplitude regimes become more sensitive to the sheet thickness of the Ti alloy as the sheet thickness is comparable to the length scale of the Widmanstätten colonies. The basic mechanism of such length scale-sensitive fatigue properties in the Ti alloy was elucidated.