Growth and crystallography of the unidirectionally solidified Al-Al4Ca eutectic

Growth and crystallography of the unidirectionally solidified Al-Al4Ca eutectic

METALLIC MATRICES Compressive properties of the unidirectionally solidified Sb-Ge eutectic Sahoo, M., Baragar, D. and Smith, R.W. Journal o f Material...

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METALLIC MATRICES Compressive properties of the unidirectionally solidified Sb-Ge eutectic Sahoo, M., Baragar, D. and Smith, R.W. Journal o f Materials Science Vol 13 (1978) pp 1565-1575 The Sb-Ge faceted/faceted eutectic has been unidirectionally solidified over a wide ranuge of growth rates in a s t u d y o f s t r u c t u r e andcompressivc properties, and are compared with faceted/non-faceted AI-Si and Zn-Ge eutecties. The compressive strength is independent of the scale of the microstructure as modified by growth rate, but additions of reeoding elements led to dramatic decreases attributed to decreased Sb-Ge interface energy. Sb primaries control strength as they case crack propagation, A directionaily solidified Ni-base eutectic alloy reinforced by a mixed hafnium-zirconium monocarbide Kim, Y.G. Journal of Materials Science Vol 13 (1978) pp 759-765 This directionally solidified alloy was found to contain up to 8% by volume of rod or ribbon shaped carbide fibres in a matrix also containing45% of coherent Ni3A1 (7') precipitate, this adding to the matrix strengthening. The crystallographic orientations of both fibre and matrix were determined by x-ray techniques to be parallel to the (100) direction. The stability of the fibres under thermal cycling between 425°C and 1100°C proved to be excellent. The effect of ply lay-up sequence on the fracture toughness of boron aluminium Prewo, K.M. Journal of Composite Materials Vol 12 (January 1978) p 40 The ply lay-up sequence of 0°/90 ° cross plied composites affects the fracture morphology which governs the degree of matrix deformation blunting the crack tip. The proportion of 0 ° and 90 ° plies is the major factor controlling this behaviour, and the resulting fracture toughness is simply calculated with a rate of mixtures approach, Effects of composition and microstructure on fatigue of "Y/7' 6 type eutectic alloys Grossman, J.E. and Stoloff, N.S.

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Metallurgical Transactions Vol 9A (January 1978) p 117 Tension-tension fatigue tests have been performed on two directionally solidified alloys of Ni, Nb and Al with 0% and 6% Cr as a function of growth rate, solution treatment and ageing. The 0% Cr alloy, which failed in a ductile fashion, had a superior fatigue resistance to the brittle 6% Cr alloy. Doubling the growth rate improved the high stress fatigue resistance of the 0% Cr material. Partial heat treatment increased the high stress fatigue life of the 0% Cr material, but full treatment reduced the intermediate stress fatigue life. This behaviour is accounted for in terms of differences in microstructure. Fracture of laminates combining 2024-T3 and 7075-T6 aluminium alloys Alic, J.A. and Danesh, A. Engineering Fracture Mechanics Vol 10 (1978) pp 177-186 The crack growth resistance curves for laminates of each alloy and combinations of the two show that the hybrid laminates have intermediate properties. This behaviour stems from the weak bonding between the laminae (using epoxy cement), and has important implications for the use of such laminated structures in crack divider applications, Friction and wear properties of aluminium-partieulate graphite composites Tokisue, H. and Abbaschian, G . J .

Materials Science and Engineering Vol 34 No 1 (June 1978) pp 75-78 Aluminium alloy matrix composites containing 3, 6 and 9 wt% particulate graphite were produced and their friction, wear, and tensile properties were determined. The composite fabrication process consisted of adding nickel- coated graphite particles to a partially solidified and vigorously agitated AI-7%Si-I%Mg alloy, followed by rcmelting and casting into ingots, The coefficients of friction and wear of the as-cast and liquid-forged composites were determined by a Falex lubricant test machine. It was found that the friction and wear properties of both as-cast and liquid-forged alloys considerably improved with addition of graphite, While the tensile strength and ductility of composites containing

3% graphite were comparable with those of the matrix, increasing graphite content reduced these properties.

Growth and crystallography of the unidirectionally solidified AI-AhCa eutectic Pellegrini, G., Gabetta, G. and Piatti, G. Materials Science and Engineering Vol 34 No 2 (July 1978) pp 171-181 The growth morphology and crystallography of unidirectionally-solidified AI/AhCa eutectic were studied over a growth range of 1-60 cm/h and using a thermal gradient of 100-110°C/cm. It was found that a transition from a regular to cellular microstructure occurs at a thermal gradiant/growth rate ratio of 5 × 104 °C.s/cm 2. Kinking as a mode of structural degradation in carbon fibre composites Evan, A.G. and Adler, W.F. Acta Metallurgica Vol 26 (1978) pp 725-738 With localised impact loading the carbon fibre/carbon matrix composites of this stud?, failed bv 'kinking' - a co-operative microbuckling of the fibres. A thermodynamic analysis of the kinking phenomenon accounts for the kink inclination and boundary orientation, and highlights the role of plastic work in the matrix and the fibre stremzth distribution. Interface interaction during fabrication of aluminium alloy-alumina fibre composites Levi, C.G., Abbaschian, G.J. and Mehrabian, R. Metallurgical Transactions A. Vol 9A (May 1978) p 697 Aluminium alloy - alumina fibre composites fabricated by incorporation of discontinuous fibres into a slurry of partially solidified alloy exhibited good wetting and the formation of an intimate void free bond between fibre and matrix. The interface region showed a significantly altered micro-structure, consisting of a Ald)3 aluminates, oxides of alloying elements, and intermetallic compounds. Fracture surfaces of composites indicate this interface has a high load transfer capability.

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