Dwell-Fatigue Behavior of a Near α Ti 6242 Alloy

摘要

For over three decades, aeroengine manufacturers are confronted to the phenomenon ofrnroom temperature dwell-effect consisting in a decrease in structure life due to the introduction ofrnhold periods at the maximum stress of the pure cyclic loading waveform. Even if many studies havernbeen conducted to analyze the parameters responsible of this life decrease the so called “dwellrneffect” remains not completely understood. The present paper focused on damage occurring duringrnpure cyclic, dwell fatigue and creep tests on a β-forged Ti-6242 alloy. It results from SEM andrnTEM analysis that crack initiation occurs by coalescence of shear-induced cavities nucleated at α/βrninterfaces in large colonies of α laths nearly parallel to the loading axis. The density and averagernsize of cavities were larger in dwell-fatigue and creep than in fatigue.