Effects of Microstructural Anisotropy on the Dwell Fatigue Life of Ti-6Al-4V Bar

Cyclic fatigue, dwell fatigue and crack growth properties were evaluated in the axial direction (L) transversal (T) of Ti-6Al-4V forged round bar. In SN curve where stress is normalized by 0.2% proof stress, cyclic life L/T almost same, whereas T as short 1/5. ductile fracture occurred when maximum was higher than 95% stress. At stresses below 870 MPa, inelastic strain range increase rate gradually decreased with decreasing mode transitioned to that growth. The gradual change must have been caused mixture anisotropic microtexture regions. 825 rapidly L direction, soft oriented regions dominant. low ΔK region (≤15 MPa√m), about twice radial shorter under conditions showing explained significantly earlier initiation compared faster along