The effect of molybdenum on the microstructure and creep behavior of Ti–24Al–17Nb–xMo alloys and Ti–24Al–17Nb–xMo SiC-fiber composites

Quast, Jeffrey; Boehlert, C. J.

doi:10.1007/s10853-008-2582-5

Cited by 9 publications

(5 citation statements)

References 29 publications

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“…The fibre/matrix debond location was identified to be within the carbon layers at the fibre-matrix interface and the debond strength was found to be almost negligible. The low debond strength between the carbon layers in the interface is in agreement with several previous studies of continuously-reinforced MMCs containing SiC-based fibres [20,[24][25][26][27][28].…”

Section: Discussionsupporting

confidence: 92%

“…Where V is the volume fraction of the fibre, η = E f / E m and E f and E m are the fibre and matrix Young's modulus, 390 GPa and 120 GPa respectively, Δα = (α m -α f ) where α f and α m are the coefficients of thermals expansion for the matrix and fibre, 4.65 x 10 -6 /°C and 10.0 x 10 -6 /°C respectively [20], ΔT is the stress free temperature minus the current temperature, which was estimated to be 500°C in this case, and ν is the Poisson's ratio of the composite, which was 0.25 [20].…”

Section: Resultsmentioning

confidence: 99%

“…The onset of debonding was identified using the onset of nonlinearity in the stress versus strain plot. The debond stress was estimated using analytical techniques based on previous work [20]. Scanning electron microscopy (SEM) was used to identify the location of the debond Fig.…”

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confidence: 99%

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Evaluation of the Fibre-Matrix Debond Strength of a Ti-22Al-23Nb (AT.%)/Trimarc Metal Matrix Composite

LeBoeuf

Boehlert

2010

Advanced Composites Letters

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Silicon carbide fibre reinforced titanium metal matrix composites are of interest for engineering applications which require high strength, high temperature, low weight and damage tolerance [12-14]. Developing experimental methods to characterize and analyze their mechanical properties is of critical importance so that deformation and failure mechanisms can be established. It has been found that mechanical test specimen geometry is important for determining the fibre-matrix debond strength in continuous fibre reinforced metal matrix composites (MMCs) [2,4-8,10,11,15-19]. Specimens containing exposed fibres lead to edge stress singularities at the fibre/matrix interface for fibre orientations which are perpendicular to the applied stress. This stress singularity leads to fibre/matrix debonding at the specimen edge without the application of an externally applied mechanical load. Accurate determination of the debond strength is difficult using such a specimen geometry. A cruciform specimen geometry mitigates this edge effect by requiring the greatest stresses to be at the centre of the sample, thereby forcing the debond to occur at the centre of the cruciform [2,4-8]. Fig. 1 gives the dimensions of the experimental cruciform specimen designed to promote debond occurrences at the centre of the cruciform. The centre wing has been added to the traditional dogbone specimen so that the free edges of the wing are stress free. The largest stress occurs in the centre region of the specimen. The strain can be measured at this location using a strain gage placed Letter

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Section: Discussionsupporting

confidence: 92%

Section: Resultsmentioning

confidence: 99%

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Evaluation of the Fibre-Matrix Debond Strength of a Ti-22Al-23Nb (AT.%)/Trimarc Metal Matrix Composite

LeBoeuf

Boehlert

2010

Advanced Composites Letters

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“…Secondly, Mo atoms will contribute to the formation of the O phase when they diffuse into the matrix, as the Mo element is also an O phase stabilizer [21].…”

Section: Methodsmentioning

confidence: 99%

Effect of C/Mo duplex coating on the interface and tensile strength of SiCf/Ti-21Al-29Nb composites

Wang

Yang

et al. 2017

Journal of Alloys and Compounds

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Abstract:SiC fiber-reinforced Ti-21Al-29Nb matrix composites with either C and C/Mo duplex coatings were prepared by the foil-fiber-foil (FFF) method, in order to comparatively study the effects of C/Mo duplex coatings on the interface and mechanical properties of the composites. The longitudinal tensile strength of the as-prepared composites was measured at room temperature. In order to study the interfacial thermal stability and microstructure evolution characteristics of the composites, vacuum thermal exposures of the composites were carried out at 800, 900 or 940 °C for different durations. The interfacial microstructures of the as-prepared and thermally-exposed composites were investigated by means of scanning electron microscopy (SEM) and X-ray energy dispersive spectroscopy (EDS). The results indicate that the C/Mo duplex coating does not only have better thermal stability, but also can further slow down the interfacial reaction of the composites in comparison with the C single coating. The diffusion of a small amount of Mo atoms made the matrix close to the interface have better plasticity, so the tensile strength of the composites can be further improved. The interface of the composite with the C/Mo duplex coating was nearly intact after the 940 /50 h thermal exposure while that of the composite with the C single coating was not intact, as the C/Mo duplex coating can better relax the thermal residual stresses than the C single coating.

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“…[29][30][31][32] Alloys containing Nb less than 12 at. pct have a two-phase microstructure a 2 (hcp structure based on Ti 3 Al) and the high-temperature phase b/B2 (bcc structure).…”

Section: Introductionmentioning

confidence: 99%

Oxidation and Diffusion in Ti-Al-(Mo, Nb) Intermetallics

Ramachandran

Mantha

Williams

et al. 2010

Metall Mater Trans A

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The oxidation resistance of Ti-Al intermetallics is superior to many of their counterparts at high temperatures. High-temperature stability of these intermetallics appears to improve with a ternary alloying addition such as Mo, Nb, etc. A detailed analysis of oxidation of the Ti 3 Al intermetallics, Ti 3 Al-2.9 at. pct Mo and Ti 3 Al-1.1 at. pct Nb, in pure oxygen using crystallographic and microscopic techniques is presented here. The alloy containing 1.1 at. pct Nb did not show an improvement in oxidation resistance over the base alloy but that containing 2.9 at. pct Mo showed marked resistance to oxidation. Activation energies of oxidation for both the alloys were comparable with those reported in the literature for similar compositions. TiO 2 and Al 2 O 3 were the major phases present in the oxide scales of the oxidized alloys. The crystal orientations from the X-ray diffraction (XRD) patterns and the morphologies from scanning electron microscopy (SEM) were in good agreement and were helpful in further analysis of the oxidation process. The effective diffusion of oxygen in the oxide layers was calculated using the mole fraction of individual oxide and the diffusivity of oxygen in pure oxide. The activation energy for the effective diffusion of oxygen through the oxide layers was determined to bẽ 24 kJ/mol. The activation energy for the oxidation process was higher than that of the diffusion of oxygen. Hence, it can be concluded that the oxidation process in both the alloys studied is not diffusion controlled.

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The effect of molybdenum on the microstructure and creep behavior of Ti–24Al–17Nb–xMo alloys and Ti–24Al–17Nb–xMo SiC-fiber composites

Cited by 9 publications

References 29 publications

Evaluation of the Fibre-Matrix Debond Strength of a Ti-22Al-23Nb (AT.%)/Trimarc Metal Matrix Composite

Evaluation of the Fibre-Matrix Debond Strength of a Ti-22Al-23Nb (AT.%)/Trimarc Metal Matrix Composite

Effect of C/Mo duplex coating on the interface and tensile strength of SiCf/Ti-21Al-29Nb composites

Oxidation and Diffusion in Ti-Al-(Mo, Nb) Intermetallics

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