Microstructural effects on fatigue and dwell-fatigue crack growth in α/β Ti-6Al-2Sn-4Zr-2Mo-0.1Si

Abstract

This article presents the results of an experimental and theoretical study of the effects of microstructure on room-temperature fatigue and dwell-fatigue crack growth in Ti-6242. The crack growth rates and micromechanisms of long crack growth are elucidated for equiaxed, elongated, and colony microstructures. The article shows that dwell and pure fatigue crack growth rates are generally similar in the long crack growth regime. The underlying mechanisms of long crack growth are also generally similar under pure fatigue and dwell-crack growth conditions. However, differences in dwell and fatigue sensitivities are observed between the different microstructure in the mid-and high-⌬K regimes. These are explained by considering the possible interactions between fatigue and creep during dwell fatigue loading at room temperature. Linearized fracture mechanics crack growth laws are presented for the modeling of crack growth in the near-threshold, Paris, and high-⌬K regimes.

Al-Ti-Containing Lightweight High-Entropy Alloys for Intermediate Temperature Applications

“…The hardness of the AlCrMoTi (#4) and AlCrMoTiV (#7) solid solutions were compared with that of other HEAs and commercial alloys and is summarized in Table 2 [26][27][28][29][30][31]. The hardness of the AlCrMoTi (#4) and AlCrMoTiV (#7) were 606 ± 11 and 556 ± 25 HV, respectively.…”

Prediction of Cold Dwell-Fatigue Crack Growth of Titanium Alloys

“…The prior research on titanium alloys attributes dwell sensitivity to many deleterious mechanisms. These mechanisms involved many factors, such as timedependent strain accumulation [4][5][6], microstructure and micro-texture influences [1,[7][8][9], stress ratio effects [10,11], internal hydrogen content [12,13] and environmental effects [14,15], crystallographic orientation dependence [5,16], interactions between creep and fatigue [17]. However, there is no consensus on the basic cause of the dwell-fatigue sensitivity of titanium alloys.…”

Observations of Facet Formation in Near-α Titanium and Comments on the Role of Hydrogen

“…As mentioned by Brandes, [9] there are contradicting reports in the literature on the effect of dwell periods on fatigue crack propagation rates. [15,26,[69][70][71][72][73][74] Some researchers find increased crack growth rates, whereas others measure no difference, and some even find reduced growth rates. The relevance of these studies has been called into question, [9] however, because they generally focused on long cracks growing in air as opposed to internally initiated cracks that are not surface connected, which are growing in a vacuum.…”