Abstract
Cold dwell fatigue is a well-known problem in the titanium components of aircraft engines. The high temperature and low dwell stress of in-service conditions have been reported to give rise to dwell fatigue resistance through a thermal-mechanical alleviation process. Here, dwell fatigue tests at room temperature and the component operating temperature were performed on IMI834 titanium alloy to assess the microstructural effects on thermal-mechanical alleviation of cold dwell fatigue while eliminating the effect of chemical composition. The ratcheting strain rates under different loading conditions were quantitatively investigated to aid the understanding of thermal-mechanical alleviation.
Highlights
Titanium alloys are widely used in manufacturing high-stressed components of aeroengines due to their high strength-to-weight ratio and good corrosion resistance [1,2,3,4,5]
Experimental [14,15,16,17] and analytical [18,19,20,21,22] observations have shown that the dwell and strain rate sensitivity is associated with the microstructure of titanium alloys
The strain rate sensitivity exponent m can be determined from the stress-drop during the strain hold period given by [33]
Summary
Titanium alloys are widely used in manufacturing high-stressed components of aeroengines due to their high strength-to-weight ratio and good corrosion resistance [1,2,3,4,5] These titanium components have been found to suffer from cold dwell fatigue since the 1970s [6]. Experimental work on dwell fatigue sensitivities of Ti-6Al-2Sn-4Zr-xMo (Ti-624x) alloys by Qiu et al [27] found that the Mo content apparently had a large influence on the dwell fatigue life debit Both chemical composition and microstructure were different in the Ti-624x series alloys considered, the alloys were designed to have the same nominal type of microstructure, but the average grain sizes and phase volume fractions were different. For the purpose of investigating microstructural effects on cold dwell fatigue, it is important and necessary to eliminate the composition effects of alloys
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