Effect of the oxygen content in solution on the static and cyclic deformation of titanium foams

It is well known that interstitials affect the mechanical properties of titanium and titanium alloys. Their effects on the fatigue properties of titanium foams have not, however, been documented in the literature. This paper presents the effect of the oxygen content on the static and dynamic compression properties of titanium foams. Increasing the oxygen content from 0.24 to 0.51 wt% O in solution significantly increases the yield strength and reduces the ductility of the foams. However, the fatigue limit is not significantly affected by the oxygen content and falls within the 92 MPa \ub1 12 MPa range for all specimens investigated in this study. During cyclic loading, deformation is initially coming from cumulative creep followed by the formation of microcracks. The coalescence of these microcracks is responsible for the rupture of the specimens. Fracture surfaces of the specimens having lower oxygen content show a more ductile aspect than the specimens having higher oxygen content.Il est bien connu que les interstices affectent les propri\ue9t\ue9s m\ue9caniques du titane et des alliages de titane. Leurs effets sur les propri\ue9t\ue9s de fatigue des mousses de titane n\u2019ont cependant pas encore \ue9t\ue9 document\ue9s dans la litt\ue9rature. Dans le pr\ue9sent article, on pr\ue9sente l\u2019effet de la teneur en oxyg\ue8ne sur les propri\ue9t\ue9s de compression statique et dynamique des mousses de titane. L\u2019augmentation de la teneur en oxyg\ue8ne de 0,24 \ue0 0,51 % en poids en solution accro\ueet de mani\ue8re significative la limite d\u2019\ue9lasticit\ue9 conventionnelle et r\ue9duit la ductilit\ue9 des mousses. Toutefois, la limite de fatigue n\u2019a pas \ue9t\ue9 affect\ue9e de mani\ue8re significative par une teneur en oxyg\ue8ne dans la gamme de 92 \ub1 12 MPa pour tous les \ue9chantillons test\ue9s dans le cadre de la pr\ue9sente \ue9tude. Pendant une charge cyclique, la d\ue9formation provient initialement d\u2019un fluage cumulatif, suivi par la formation de microfissures. La coalescence de ces microfissures est responsable de la rupture des \ue9chantillons. Les surfaces des fissures dans les \ue9chantillons ayant une teneur en oxyg\ue8ne plus faible exhibent un aspect plus ductile que celles des \ue9chantillons ayant une teneur plus \ue9lev\ue9e en oxyg\ue8ne.Peer reviewed: YesNRC publication: Ye

SINTERING SUPPORTS FOR TI-BASED POWDER METALLURGY COMPONENTS

Peer reviewed: NoNRC publication: Ye

Direct visualization and quantification of bone growth into porous titanium implants using micro computed tomography

The utility of porous metals for the integration of orthopaedic implants with host bone has been well established. Quantification of the tissue response to cementless implants is laborious and time consuming process requiring tissue processing, embedding, sectioning, polishing, imaging and image analysis. Micro-computed tomography (\u3bcCT) is a promising three dimensional (3D) imaging technique to quantify the tissue response to porous metals. However, the suitability and effectiveness of \u3bcCT for the quantification of bone ingrowth remains unknown. The purpose of this study was to evaluate and compare bone growth within porous titanium implants using both \u3bcCT and traditional hard-tissue histology techniques. Cylindrical implants were implanted in the distal femora and proximal tibiae of a rabbit. After 6 weeks, bone ingrowth was quantified and compared by \u3bcCT, light microscopy and backscattered electron microscopy. Quantification of bone volume and implant porosity as determined by \u3bcCT compared well with data obtained by traditional histology techniques. Analysis of the 3D dataset showed that bone was present in the pores connected with openings larger 9.4 \u3bcm. For pore openings greater than 28.2 \u3bcm, the size of the interconnection had little impact on the bone density within the porosity for the titanium foams.Peer reviewed: YesNRC publication: Ye

Interstitial elements in titanium powder metallurgy: sources and control

The effect of interstitials on the mechanical properties of cast and wrought titanium alloys has been extensively reported but less information is available on the effect of contamination during PM processing. The sources of interstitial contamination when processing titanium powders by compaction, isostatic pressing, powder injection moulding (PIM) and innovative foaming processes are reviewed, focusing specifically on oxygen. The initial powder characteristics (surface area, size), process parameters (time, temperature) and environment (atmosphere, binder, support) may all have significant impact on the final interstitial content. It is, therefore, important to identify and control the sources of contamination by interstitials. A case study on PIM is provided to illustrate the relative contribution of the different sources.Peer reviewed: YesNRC publication: Ye

Oxygen sources and control in titanium PIM process

Peer reviewed: NoNRC publication: Ye

Gas Permeation Through Perforated Metallic Foams

Peer reviewed: YesNRC publication: Ye

Morphological and mechanical comparision of injection and compression moulding in-line compounding of direct long fibre thermoplastics

Long fibre thermoplastics (LFT) based on polypropylene/glass fibre (PP/GF) composites has become one of the most widely used plastics in semi-structural and structural automotive applications in both aesthetic and non-aesthetic parts. LFT are commercially available in pre-compounded pellets for injection moulding and are developed with specific properties for targeted functions. In a rationalizing effort to reduce costs, heat histories, and create in-house flexibility of material blending in-line compounding (ILC) of base materials including resin, additives (heat stabilizers, colors, coupling agents, etc.), and glass roving reinforcements for direct moulding of LFT parts (D-LFT) has been developed in the last 10 years. Two major versions of D-LFT technology currently exist on the market, both relying on twin-screw extrusion (one-stage or two-stage) for ILC, one utilizing compression moulding and the other injection moulding. While these two technologies share several similarities, they also present significantly different features in terms of fibre length, orientation and mechanical properties for example, related to their respective processing conditions. The objective of this paper is to address some of them. A Dieffenbacher LFT Direct system, using the compression moulding process, and a Krauss-Maffei Injection Moulding Compounder (IMC), using the injection moulding process, were used to mould similar test parts that have a significant level of complexity in their geometry. Samples were taken from the parts and from machine purges for a comparison of the respective fibre distribution patterns of the two moulding technologies using micro focus X-ray computed tomography. A characterization of their fibre length distribution was also performed on these samples from pyrolysis and image analysis. Resulting mechanical properties were then added to the comparison matrix to provide a comprehensive picture of the two moulding technologies.Peer reviewed: YesNRC publication: Ye

Numerical simulation of the flow through metallic foams : multi-scale modeling and experimental validation

NRC publication: Ye