The phenomenon of “dwell sensitivity” in the α+β and near α titanium alloys and the intrinsic relationship with quasi-cleavage facet formation is discussed. In the present paper, particular emphasis is placed upon the role of “cold creep” and ambient temperature strain accumulation under cyclic loading. A process of stress redistribution between microstructurally distinct regions that demonstrate different strengths is proposed as the fundamental cause of facet development and subsequent dwell failures. A model to describe the redistribution process is validated through a matrix of fatigue testing designed to assess the effects of microstructural form, stress axiality and periods of dwell loading at peak stress on cyclic strain accumulation.

Volume Subject Area:
Manufacturing Materials and Metallurgy
Topics:
Fatigue, Power stations, Titanium alloys, Stress, Creep, Failure, Fatigue testing, Temperature
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