Publications by Andreas Mortensen

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We study the response to age hardening of Al-4.5%Cu replicated foams with 75 and 400 pm cell sizes and with varying relative densities. The 400 mu m cell size foams have a similar behavior to the bulk alloy, whereas the 75 pm cell size foams with relative ...

The influence of capillarity on the near-plane front solidification of metal matrix composites is examined by analysis of the one-sided solidification of a binary alloy in a planar interstice of constant width in the limit of low Peclet number. We assume that in this limit, solute isoconcentrates in the liquid are everywhere orthogonal to the growth direction. Capillarity causes the alloy to solidify in a cellular mode, even in the absence of constitutional supercooling. Two solution branches are derived fo

Open-pore 99.99% pure Al and Al-5 wt.% Mg foam produced by replication, with pores either 400 or 75 gm in average diameter, are tested in compression with repeated relaxation cycles, at room temperature. Similar data are collected on pure aluminium. Estima ...

This work probes the influence of wetting on pressure infiltration. Pressure/saturation curves for the infiltration of packed F1000 angular alumina particle preforms by liquid Cu-Al and Sn-Al alloys are measured using an instrumented high-temperature press ...

The flow and failure behaviour of replicated pure aluminium foams in the presence of holes and notches is explored, varying the pore size and the notch depth or hole radius. Flat dog-bone tensile specimens containing a cylindrical hole, and cylindrical V-n ...

The influence of applied stress on the equilibrium shape of a liquid intergranular inclusion is derived to show that (i) results differ significantly from those for a void, and (ii) this difference explains the experimental data if liquid inclusions behave ...

Single-crystalline cast aluminium microwires with a diameter near 15 are characterised by Laue microdiffraction. A microwire in the as-cast condition exhibits a misorientation below over a length of 500 . The measured density of geometrically necessary dis ...

The kinetics of the initial stage of uniaxial vacuum-hot-pressing of commercially pure spherical titanium powders are investigated for temperatures between 730 and 870-degrees-C and applied pressures from 25 to 50 MPa. Densification kinetics are found to agree with models of Arzt, Ashby and coworkers for hot isostatic pressing by power law creep. The best fit with all data is for a creep exponent of 4.9 and a creep activation energy of 208 kJ mol-1. With the addition to the titanium powder of 10 vol.% TiC p

Pressure infiltration of liquid metal is one of the most important processing routes for the production of aluminum-matrix composites having a self-supporting reinforcement phase. This article briefly examines the physical phenomena governing infiltration processes, to present practical guidelines derived from their analysis for optimization of the process and the materials produced. Engineering aspects that are pertinent to infiltration techniques, including preform preparation, process configurations, flo

Microprobe tips are commonly used to perform in-situ micromechanical tests within an electron microscope. In service, such tips have a tendency to accumulate along their surface a layer of deposited material. Tip cleanliness is crucial in order to obtain r ...

The tensile behaviour of composites produced by infiltrating ceramic particle beds with high purity (99.99%) At is studied as a function of reinforcement size and chemistry (Al2O3 and B4C). The yield stress is higher in composites containing B4C particles, increasing with decreasing interparticle distance in both composite systems. The flow stress of the composites, when corrected for damage, displays the same dependence on interparticle distance as the yield stress. The overall strain hardening exponent, h

We compare the uniaxial tensile behavior of mu m-scale cast silver tensile specimens at strain rates of 10(-3 )s(-1) and 2 s(-1) to find no major impact of the strain rate on either of the flow stress, work hardening, or strain to fracture. Plastic deforma ...

Acoustic Emission (AE) is used to characterize the plastic deformation of open-cell pure aluminum foams produced by salt replication. Measurements were performed on samples with cells 25, 75 or 400 μm in average diameter, all with a relative density near 24%. AE signals were measured during compression tests conducted with a constant cross-head speed. Deformation is uniform along the porous metal samples. Recorded AE accompanying plastic deformation of the cellular structure exhibits intermittent behaviour,

This data article presents a methodology and the corresponding code developed to perform and process stress relaxation tests where samples display superimposed (i) classical, continuous logarithmic relaxation together with (ii) sudden displacements manifes ...

The oxide film present along the interface between metal and pores in microcellular aluminium produced by replication depends on the leaching medium that is used to dissolve the NaCl preform: leaching in water produces a thick and irregular multilayered hy ...

Drainage curves (plots of the non-wetting fluid saturation versus applied pressure) for infiltration of SiC particle preforms with Al and Al-12.2 at.% Si are measured at 1023 K (750 degrees C) with a pressure infiltration apparatus adapted for direct track ...

We measure, using an adaptation of a method designed for ceramic ball bearings, the local strength of a brittle second phase that serves to reinforce a metal. The method uses focused ion beam milling and a nanoindentation device, and is free of artifacts c ...

Andreas Mortensen

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Age-Hardening Response of Replicated Microcellular Al-4.5%Cu

Analysis of steady-state shallow cell solidification in metal matrix composites

Permeability of open-pore microcellular materials

Activation volume in microcellular aluminium: Size effects in thermally activated plastic flow

Influence of the wetting angle on capillary forces in pressure infiltration

Hole and notch sensitivity of aluminium replicated foam

Young's modulus of ceramic particle reinforced aluminium: measurement by the Impulse Excitation Technique and confrontation with analytical models

Equilibrium shape of a liquid intergranular inclusion in a stressed elastic solid

Laue microdiffraction characterisation of as-cast and tensile deformed Al microwires

Initial-Stage Hot-Pressing Of Monosized Ti And 90-Percent Ti-10-Percent Tic Powders

Pressure-Infiltration Processing Of Reinforced Aluminum

A method for cleaning flat punch diamond microprobe tips

Size dependent strengthening in particle reinforced aluminium

Intermittent tensile deformation of silver microcastings: Influence of the strain rate

Deformation of Open-Cell Microcellular Pure Aluminum Investigated by the Acoustic Emission Technique

Stress relaxation in the presence of sudden strain bursts: Methodology and stress relaxation data of microcast aluminium microwires

Surface oxide in replicated microcellular aluminium and its influence on the plasticity size effect

Uniaxial deformation of microcellular metals

Direct measurement of drainage curves in infiltration of SiC particle preforms

The local strength of microscopic alumina reinforcements