A MICROSTRUCTURAL STUDY OF FATIGUE FAILURE IN Ti-15V-3Cr-3Sn-3Al ALLOY

摘要

Ti-15-3 alloy thin plate specimen having two different microstructures has been cyclically stressed in alternating plane bending to clarify the fatigue failure micromechanism of P titanium alloys. Microstructures of the specimen were controlled by the heat treatment in two ways: as solution-treated (specimen S), and as solution-and-aging treated (specimen S+A). Fatigue tests were conducted at R = -1, at room temperature and in air. Specimen S was better in fatigue properties than specimen S+A. Fatigue cracks in both specimens propagated in transgranular mode. Fracture surface topography appeared more brittle in specimen S than in specimen S+A. It was found from microstructural examinations that fatigue failure micromechanism depended on the applied stress amplitude in specimen S and on the configuration of the α-phase platelets precipitated in specimen S+A during the heat treatment.