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.

Issue Section:
Gas Turbines: Manufacturing Materials and Metallurgy, and Marine
Keywords:
fatigue, fractography, aluminium alloys, crystal microstructure, internal stresses, stress analysis, deformation, gas turbines
Topics:
Creep, Failure, Fatigue, Stress, Titanium alloys, Power stations, Alloys, Temperature, Gas turbines, Tension
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