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Abstract

This work analyzes the effect of precipitation of nanoscale α laths on slip activity in three ultrastrong β Ti-xAl-yMo-zV alloys. It is shown that α precipitates act as selective barriers for {1 1 0}β slip, offering comparatively higher resistance to low Schmid factor (SF) systems (anomalous slip), which are suppressed following precipitation. This study reveals a dominant role of the global SF over geometrical factors in β-α-β slip transfer in densely aged β Ti alloys.

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... Crystallographic orientations between α and β phases are related by the Burgers orientation relationships (BOR) under certain circumstances [11] . This feature plays a key role in the slip transfer processes across α/ β interfaces, which contributes to a noticeable tensile anisotropy [12][13][14][15][16] . Incompatibility stresses arising from elastic anisotropies of α and β phases have been considered for a long time [ 17 , 18 ]. ...
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High strength metastable β titanium alloys are widely used in the aerospace industry for their superior mechanical properties, including an outstanding strength-to-weight ratio. Although prior studies have suggested a major influence of the elastic anisotropies of α and β phases on deformation, the understanding of the onset and the development of plasticity at the β grain scale is still limited. Strain localization was presently investigated in various Ti alloys with different microstructures. In-situ optical microscopy tensile tests were carried out in combination with digital image correlation and electron back-scattered diffraction in order to relate the local deformation behavior with the microstructure. The low directional modulus along the [001] direction of β phase was observed to generate high incompatibility stresses, which governs the onset of slip activity and strain localization. However, it was found to emerge differently depending on the presence of α phase. In α phase free microstructures, high incompatibility stresses across β grain boundaries triggers the onset of {112}〈111〉 slip on the side exhibiting the highest stiffness. In α+β microstructures, β grains with a [001] direction aligned with the loading direction were found to experience an early onset of plastic deformation and subsequent strain localization. A mechanistic understanding was obtained through the simulation of micromechanical fields in α and β phases. The behavior of polycrystalline aggregates with explicit modeling of hierarchical dual phase microstructure inherent to β grains was studied within an anisotropic elasticity framework using fast-Fourier transforms-based simulations. An early onset of plastic deformation was found to occur in α phase embedded in [001] oriented β phase as compared to other β orientations due to stress partitioning driven by the stiffness difference. The effects of the Burgers orientation relationships, the β phase fraction and the selected set of single crystal elastic constants on stress heterogeneity were also examined and discussed.
... Metastable β titanium alloys are attracting the interest in aerospace, marine, and medical industries due to their superior properties such as high specific strength, excellent corrosion resistance, and suitable cold formability [10,11]. TB8 (Ti-15Mo-3Al-2.8Nb-0.2Si) is a kind of high strength and ductility metastable β titanium alloy developed by China, which is similar to American β-21S alloy in chemical composition [12]. ...
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Chapter
IntroductionMetallurgy and ProcessingMechanical Properties Tensile PropertiesFracture ToughnessFatigue (HCF)Fatigue Crack Propagation (FCP)ApplicationsReferenced Literature and Further Reading Tensile PropertiesFracture ToughnessFatigue (HCF)Fatigue Crack Propagation (FCP)
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