Publications de Andreas Mortensen

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We present a process for the production of Cu-Al matrix composites containing between 25 and 30 vol.% in situ Al2O3. The composites are prepared by pressing, heat-treating and hot working blended powders of Cu, Al and CuO packed into copper alloy cans. The ...

We explore the influence (i) of the interaction between aluminium and alumina, and (ii) of sodium impurities present in Bayer alumina, on the pressure infiltration of alumina particle preforms with molten aluminium. At 1000°C or above, although the alumini ...

A computational analysis of the longitudinal deformation of continuous fibre reinforced metals is presented. Elastic and elastic-plastic matrix behaviour are considered. Analytical approaches are confronted with finite element analyses (FEA) for varying fi ...

A microscopic three-point bending test that measures the strength of faceted particles of high aspect ratio is developed and used to probe individual coarsened plate-like silicon particles extracted from the eutectic Al-12.6%Si alloy. Focused ion beam mill ...

We consider a binary hypoeutectic alloy casting which solidifies in dendritic form in an unreinforced engineering casting and seek to predict its microstructure in a metal matrix composite. We focus on the case where the reinforcement is fixed in space and fairly homogeneously distributed. We assume that the reinforcement does not catalyze heterogeneous nucleation of the solid. We show that the reinforcement can cause several microstructural transitions in the matrix alloy, depending on the matrix cooling r

Aluminium (Al 99.99 % purity) and aluminium alloy Al-5.7Ni and Al-5Mg (wt.%) open-cell foams made by replication processing are creep-tested in the temperature range T/Tm=0.5-0.8, varying the relative density between 0.10 and 0.25. Steady state creep rates are measured and interpreted on the basis of analytical models developed using the variational estimate of Ponte Castañeda and Suquet, as well as the beam engineering model developed by Andrew-Gibson-Ashby. The steady state creep rate, in foams produced o

Aligned nickel wire bundles 4 to 5 cm in length and up to 2.5 cm in diameter are infiltrated by pure aluminum using gas-assisted infiltration, to produce samples having global compositions in the range of 40 to 76 at, pet nickel. As-reacted sample macrostructures feature a large single-phase region of NiAl independent of applied pressure and nickel preform volume fractions in the ranges of 0.15 to 0.3 MPa and 0.23 to 0.44, respectively. These macrostructures also contain, in some cases, either an aluminum-r

We present dynamic measurement of drainage curves in two systems having relevance to metal matrix composite processing, namely SiC/Al and SiC/Al-12.2at%Si. Data show that liquid/solid chemical reactions that cause a lowering of the contact angle do indeed ...

Interfaces in metal and ceramic composites differ from interfaces in polymer matrix composites inasmuch as: (i) fiber degradation due to chemical reaction with the matrix at processing temperatures is frequent and (ii) bonding at the interface is generally chemical in nature (i.e. features primary chemical bond formation across the interface). Elementary analysis of requirements placed on the interface for mechanical property optimization indicate that, for toughening by fiber debonding and pull-out, very w

Over the past two decades, means allowing to probe experimentally the mechanical behavior of materials specimens only a few micrometers or less in diameter have multiplied, largely owing to the widespread adoption and versatility of focused ion beam (FIB) ...

Monocrystalline, cast aluminium microwires of diameter (D) below 25 mu m free of micromilling artefacts are annealed under protective atmosphere. Annealing increases the flow stress of all tested microwires, by an amount that is found, in a Haasen plot of ...

The evolution of microstructural damage during tensile deformation of pure aluminium reinforced with 10 vol.% alumina short fibres is studied by monitoring the evolution of density and Young's modulus as a function of tensile strain. It is found that Young ...

The wetting of angular alumina particle preforms by Cu-Sn alloys is investigated by means of pressure infiltration experiments conducted at 1150 A degrees C, using a system enabling dynamic and precise measurements of the metal volume injected into the pre ...

Room-temperature fracture along the (111) plane of silicon is probed at the micron-scale using chevron notched cantilever beams that enable stable crack growth before unstable fracture in successful tests. The main experimental observation is that a growin ...

It is proposed that a critical combination of matrix strain hardening exponent and fibre volume fraction must be exceeded to confer attractive tensile ductility to short-fibre reinforced metal. © 2005 Acta Materialia Inc. Published by Elsevier Ltd. Al ...

Solution-reprecipitation during liquid phase sintering can lead to gravity-aligned gradients in the amount of refractory phase as a result of the interaction between gravitational forces and capillary forces. We provide an analysis of this mechanism for gradient formation and show that for most important engineering materials, solution-reprecipitation does not cause substantial gravity-induced gradients. This conclusion is in agreement with published data for tungsten heavy alloy materials containing volume

We use the long-wavelength model of Hutchinson and Neale (1977) and Ghosh (1977) to estimate the uniform tensile elongation of two-phase composites deforming quasistatically according to the equistrain rule of mixtures, in which one phase is ductile while ...

We show that uniaxial compression testing of spherical particles can give unambiguous access to their tensile strength as governed by surface flaws if one uses pairs of elasto-plastic platens, tailoring their hardness in order to control the relative area ...

Chalcogenide glass exhibits a wide transmission window in the infrared range, a high refractive index, and nonlinear optical properties; however, due to its poor mechanical properties and low chemical and environmental stability, producing three-dimensiona ...

Silver chloride containing particles of irregular form of the order of 1-mu-m in diameter is used as a model material for particle-reinforced metal matrix composites (MMCs). Matrix dislocations due to the mismatch of the coefficients of thermal expansion of the two phases are made visible to transmission optical microscopy through bulk decoration performed at room temperature. The plastic zone around the particles takes two forms, similar to what is observed around the glass microspheres: (a) rows of coaxia

Andreas Mortensen

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In situ copper–alumina composites

Kinetic processes in the high-temperature pressure-infiltration of Al into Al2O3

Longitudinal deformation of fibre reinforced metals: Influence of fibre distribution on stiffness and flow stress

Microscopic strength of silicon particles in an aluminium–silicon alloy

Solidification of binary hypoeutectic alloy matrix composite castings

Creep behaviour of replicated open-pore aluminium and aluminium alloy foams

Reactive infiltration processing of aluminum-nickel intermetallic compounds

Direct measurement of drainage curves in infiltration of SiC particle preforms: influence of interfacial reactivity

Interface chemistry of inorganic composite materials

On the preparation and mechanical testing of nano to micron-scale specimens

The effect of size on the plastic deformation of annealed cast aluminium microwires

Damage evolution in Saffil alumina short-fibre reinforced aluminium during tensile testing

Infiltration of tin bronze into alumina particle beds: influence of alloy chemistry on drainage curves

Stable room-temperature micron-scale crack growth in single-crystalline silicon

Ductility of Saffil(TM) short fibre reinforced metals

The effect of gravity on solution-reprecipitation during liquid phase sintering

Tensile elongation of unidirectional or laminated composites combining a brittle reinforcement with a ductile strain and strain-rate hardening matrix

Compression testing spherical particles for strength: Theory of the meridian crack test and implementation for microscopic fused quartz

Glass-in-glass infiltration for 3D micro-optical composite components

Thermal mismatch dislocations produced by large particles in a strain-hardening matrix