Influence of Oxygen on the Fatigue Behaviour of Ti-6Al-7Nb Alloy

Hidalgo, Alexandra Amherd; Ebel, Thomas; Limberg, Wolfgang; Pyczak, Florian

doi:10.4028/www.scientific.net/kem.704.44

Cited by 15 publications

(4 citation statements)

References 7 publications

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“…The oxygen levels of some as-sintered parts were roughly adjusted by a special heat treatment in mixed argon-oxygen gas at 500°C for different dwell times before final sintering after pre-sintering stages (700°C/1hr) [13]. The carbon levels of some as-sintered parts were increased significantly to generate high carbon contamination by using a comparably ‘dirty’ retort without any burn-out clean-up programmes in advance.…”

Section: Methodsmentioning

confidence: 99%

Influence of defects on damage tolerance of Metal-Injection-Molded β titanium alloys under static and dynamic loading

Ebel

Pyczak

et al. 2022

Powder Metallurgy

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The β titanium alloys are key materials in lightweight and biomedical applications, due to the combination of excellent biocompatibility and mechanical properties. However, the Binderbased Powder Technologies such as Metal-Injection-Molding (MIM), Binder-Jetting and Fused-Filament-Fabrication, normally introduce three major processing-related defects in the as-sintered Ti-parts: (i) residual porosity, (ii) high impurity level and (iii) coarse-grained structure. The previous studies revealed that these processing defects invariably tend to be even more severe in β titanium alloys than in α/β Ti-6Al-4V alloy, all fabricated by powder metallurgical route. In this work, these processing defects and their likely origins in MIM β titanium alloys are analysed. Furthermore, the influence of these defects on damage tolerance and fracture mechanisms of MIM β titanium alloys under either static or dynamic loading is investigated. Based on the studies, strategic technical improvements in the processing to improve the reliability of MIM β titanium alloys products are proposed.

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Section: Methodsmentioning

confidence: 99%

Influence of defects on damage tolerance of Metal-Injection-Molded β titanium alloys under static and dynamic loading

Ebel

Pyczak

et al. 2022

Powder Metallurgy

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“…Bulk samples of Ti-6Al-7Nb (wt.%) were fabricated by means of sintering. The detailed synthesis route is described elsewhere [53]. Surface functionalization of Ti-6Al-7Nb was carried out by a two-stage process.…”

Section: Methodsmentioning

confidence: 99%

Surface Functionalization of Biomedical Ti-6Al-7Nb Alloy by Liquid Metal Dealloying

et al. 2020

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Surface functionalization is an effective approach to change the surface properties of a material to achieve a specific goal such as improving the biocompatibility of the material. Here, the surface of the commercial biomedical Ti-6Al-7Nb alloy was functionalized through synthesizing of a porous surface layer by liquid metal dealloying (LMD). During LMD, the Ti-6Al-7Nb alloy is immersed in liquid magnesium (Mg) and both materials react with each other. Particularly, aluminum (Al) is selectively dissolved from the Ti-6Al-7Nb alloy into liquid Mg while titanium (Ti) and niobium (Nb) diffuse along the metal/liquid interface to form a porous structure. We demonstrate that the porous surface layer in the Ti-6Al-7Nb alloy can be successfully tailored by LMD. Furthermore, the concentration of harmful Al in this porous layer is reduced by about 48% (from 5.62 ± 0.11 wt.% to 2.95 ± 0.05 wt.%) after 30 min of dealloying at 1150 K. The properties of the porous layer (e.g., layer thickness) can be tuned by varying the dealloying conditions. In-vitro tests suggest improved bone formation on the functionalized porous surface of the Ti-6Al-7Nb alloy.

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“…In contrast, Ti-6Al-7Nb specimens intended for the determination of the oxygen influence were additionally thermally treated in order to achieve different oxygen contents (Table 2). The oxidation procedure is explained in a previous publication [11]. Higher oxygen content is acquired when the specimens are exposed to longer times under oxygen-argon atmosphere at 400 °C.…”

Section: Methodsmentioning

confidence: 99%

“…In fact, oxygen acts as a potent, inexpensive alloying element for strengthening but it decreases the ductility of unalloyed titanium [1]. Surprisingly, the ductility of α/β titanium alloys processed by MIM is maintained up to 0.35 wt.% of oxygen in Ti-6Al-4V [1,2] and 0.38 wt.% of oxygen in Ti-6Al-7Nb [4]. However, influence of oxygen on the fatigue behaviour of α/β titanium alloys is still not known.…”

Section: Introductionmentioning

confidence: 99%

Influence of Alloying Elements in Fatigue Properties of α/β Titanium Alloys

Hidalgo

Limberg

Ebel

et al. 2018

KEM

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One strategy to make PM titanium components competitive in terms of mechanical properties is the addition of suitable alloying elements. PM offers the possibility to adapt the alloy composition in order to achieve the required properties. In this study, different alloying elements were introduced into α/β titanium alloys and fatigue behaviour was evaluated. Four-point bending fatigue tests with a stress ratio of 0.2 were performed on specimens manufactured by metal injection moulding (MIM) and shot peening. Results showed an enhanced sintering activity of Ti-6Al-7Nb by adding small amounts of iron. The impact on fatigue properties was evaluated. The increase of oxygen in Ti-6Al-7Nb from 0.15 wt.% to 0.45 wt.% caused a decrease in elongation from 16% to 6%. However the fatigue strength at 107cycles is just slightly reduced from 450 to 350 MPa. The addition of 0.5 wt.% yttrium powder to gas atomized Ti‑6Al‑4V powder led to a noticeable refinement of the microstructure of the sintered parts, due to the formation of Y2O3particles, which hinder grain growth. In spite of a slightly higher residual porosity, the microstructural refinement increased the fatigue strength at 107cycles from 450 to 470 MPa. At 106cycles, the fatigue strength increased even from 705 to 765 MPa. The addition of yttrium did not result in a higher oxygen pick up, which indicates a scavenging of oxygen from the titanium matrix by formation of Y2O3during sintering. Contrary to the fatigue strength results, the scavenging effect led to a decrease in tensile strength of about 70 MPa. The microstructure of fatigue-tested specimens was characterized by using optical and scanning electron microscopy.

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Influence of Oxygen on the Fatigue Behaviour of Ti-6Al-7Nb Alloy

Cited by 15 publications

References 7 publications

Influence of defects on damage tolerance of Metal-Injection-Molded β titanium alloys under static and dynamic loading

Influence of defects on damage tolerance of Metal-Injection-Molded β titanium alloys under static and dynamic loading

Surface Functionalization of Biomedical Ti-6Al-7Nb Alloy by Liquid Metal Dealloying

Influence of Alloying Elements in Fatigue Properties of α/β Titanium Alloys

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