Role of Microtexture on Fatigue Lifetime Variability and Crack Initiation Mechanisms (Preprint)

摘要

Commercial titanium alloys have demonstrated a fatigue lifetime debit in material that contains microtextured regions, as compared to material that has been processed to reduce microtexture. This result has generated commercial incentive to identify the effectiveness of various thermomechanical processing steps to remove microtexture and to determine the fatigue crack initiation mechanism in these microtextured regions. To quantify the efficacy of microtexture reduction on the fatigue behavior of alpha + beta titanium alloys, three different microstructural conditions of Ti-6Al-4V have been produced via distinct thermomechanical processing routes: an equiaxed alpha microstructure containing microtexture, an equiaxed alpha microstructure free of microtexture, and a beta annealed structure. The impact of sample orientation on fatigue behavior was examined by testing specimens along three different directions relative to the original plate reference frame; the rolling direction, the transverse direction, and 45 deg from the rolling direction for each of these.