Publications by Andreas Mortensen

Chat with Graph Search

Ask any question about EPFL courses, lectures, exercises, research, news, etc. or try the example questions below.

DISCLAIMER: The Graph Chatbot is not programmed to provide explicit or categorical answers to your questions. Rather, it transforms your questions into API requests that are distributed across the various IT services officially administered by EPFL. Its purpose is solely to collect and recommend relevant references to content that you can explore to help you answer your questions.

Aluminium-5 wt.% magnesium open cell foam produced by replication and tested in tension at 300, 350 or 450 degrees C creeps at rates between 10(-3) and 10(-8) s(-1). The behaviour of the foam matches that of the alloy from which it is made: three-power law ...

The plastic deformation of small-scale face-centered cubic metals exhibits intermittent slip burst events that appear on stress-strain curves as sudden strain jumps and/or load drops. These events are generally attributed to the avalanche-like cooperative ...

The influence exerted by the shape of randomly oriented non-conducting inclusions on the electrical conductivity of a metal is investigated using the aluminum-sit icon eutectic alloy. By varying the time and temperature of heat treatment after solidification, the shape of the silicon inclusions is varied between plate-like and close-to-spherical. The influence of the geometry of the inclusions on the resistivity of the composite is separated from the influence of varying amounts of silicon in solid solution

Dendrite tip temperature measurements are reported for the hypereutectic alloy Al-30% Si, directionally solidified as a bulk (non-composite) alloy, and also as the matrix of a fibrous metal matrix composite. Over the range of tip velocities studied (10-1000 mu m s) the primary Si tip undercooling in the directionally solidified bulk alloy increases slightly with increasing tip velocity, and indicates, by its large value, the presence of significant kinetic undercooling. This is in contrast with solidificati

The thermal expansion of three isotropic metal-matrix composites, reinforced with SiC particles or microcellular foam, is measured between 25 degrees C and 325 degrees C. All three composites show initial coefficient of thermal expansion (CTE) values in agreement with the Turner model predictions, and near Schapery's lower-elastic bound for CTE. At higher temperatures, the CTE of foam-reinforced Al decreases, while that of the two particle-reinforced composites increases. These observations are interpreted

Microcellular Al-4.5 wt pct Cu of 400- or 75-mu m average pore diameter is solidified at cooling rates ranging from -30 K/min to -0.45 K/min (-30 A degrees C/min to -0.45 A degrees C/min). In the 400-mu m pore size samples, the dendritic character is lost, ...

Fracture toughness tests are conducted at room temperature and 923 K (650 degrees C) on SENB (Single Edge Notched Bend) specimens of three different (alpha(2) + gamma ) TiAl-based alloys. One alloy is a conventional near fully lamellar Ti-45Al-2Mn-2Nb + 0. ...

Microcellular aluminium can be produced by a process known as replication; this involves the infiltration of a packed bed of NaCl particles which are subsequently leached after metal solidification. The resulting material features a uniform distribution of ...

Micron-scale shaped 2D or 2.5D structures made of silver or copper can be produced by combining silicon photolithographic etching with metal casting by pressure infiltration. This combination of two classical pro-cesses, one from semiconductor fabrication ...

Particle reinforced composites are produced by infiltrating ceramic particle beds with 99.99% Al. Resulting materials feature a relatively high volume fraction (40-55 vol. pet) of homogeneously distributed reinforcement. The evolution of damage during tensile straining of these composites is monitored using two indirect methods; namely by tracking changes in density and in Young's modulus. Identification and quantification of the active damage mechanisms is conducted on polished sections of failed tensile s

A method is presented for the simultaneous measurement of relative grain boundary energy and all five macroscopic grain boundary degrees of freedom in leaded copper. When compared to the Wynblatt–Takashima model, results suggest a lowered boundary energy w ...

Scaling exponents for the conductivity and stiffness of replicated microcellular materials exceed commonly predicted values of 1 and 2. We show here that this is caused by the fact that, in replicated microcellular materials, the solid architecture varies ...

X-ray microtomography and three-dimensional (3D) image analysis are used to quantify the structural evolution during cold isostatic compaction of two irregularly shaped NaCl powders having different mean particle sizes (75 and 400 mu m) and somewhat differ ...

The hydrostatic compaction of composites comprising a closely-packed particle-bed filled by a dense matrix is measured experimentally using a fluid-pressurization apparatus. A highly compliant polymer or pure aluminium are infiltrated into preforms of pack ...

All three classes of fibre reinforced composite materials (polymer, metal and ceramic matrix) may be produced by flow of liquid matrix into the open spaces left within pores of a fibre preform. Even though several specific issues arise from the nature of each composite matrix class, governing phenomena apply to all infiltration processes, and include in particular: (i) capillary phenomena, (ii) transport phenomena, and (iii) the mechanics of potential fibre preform deformation. These phenomena and their gov

A new process for infiltrating fibrous pre-forms with liquid metal is presented which eliminates the need for pressurization of the metal or pre-form chemical pretreatment. The molten matrix material and preform are held in a cermic crucible so that the melt forms an annulus around the pre-form. These are then subjected to an intense high frequency magnetic pulse. The eddy currents induced in the melt interact with the magnetic pulse to propel the metal into the pre-form at a high speed, infiltrating the pr

Capillary pressures encountered in composite processing are often evaluated by measuring infiltration rates as a function of applied pressure. Such data are generally interpreted assuming slug-flow. Using the Brooks-Corey correlations we relax this assumpt ...

We extend to flat surfaces the fracture toughness method presented in Acts Materialia vol. 86 (2015) p.385 and measure in this manner the fracture toughness of fused quartz. Tests give 0.67 +/- 0.01 MPa m(1/2) which agrees with earlier microscopic and macr ...

Silver chloride containing fibers, spheres and particles of irregular form is used as a model material to study plasticity in metal matrix composites. Matrix dislocations generated upon cooling by the mismatch of coefficient of thermal expansion between the matrix and the reinforcement are observed by transmission optical microscopy after decoration at room temperature by photodissociation of the matrix. The plastic zone around the fibers, spheres and particles takes two forms: (a) trains of coaxial prismat

Microsegregation in a binary alloy solidified in the form of deep cells is predicted using a simplified finite difference model. The model accounts for solid state diffusion and for flow of liquid between cells driven by solidification shrinkage. Cell tip undercooling is predicted using the expression originally derived by Bower et al. Cells are assumed to be cylindrical, and solid state diffusion along the cell axis is ignored, simplifying considerably prediction of solid state diffusion and cell shape beh

Andreas Mortensen

Chat with Graph Search

Creep of aluminium-magnesium open cell foam

On the slip burst amplitude cutoff in dislocation-rich microcrystals

On the influence of the shape of randomly oriented, nonconducting inclusions in a conducting matrix on the effective electrical conductivity

Kinetic undercooling in solidification of a hypereutectic Al-Si alloy; Effect of solidifying within a ceramic preform composite

Thermal expansion of metals reinforced with ceramic particles and microcellular foams

Solidification of Al-4.5 wt pct Cu-Replicated Foams

Fracture of convoluted and lamellar α2 + γ TiAl alloys

Uniaxial deformation of microcellular metals: model systems and simplified analysis

Coupling silicon lithography with metal casting

Quantification of microdamage phenomena during tensile straining of high volume fraction particle reinforced aluminum

Measurement and anisotropy of grain boundary energy in Cu-1 wt.% PB

Scaling of conductivity and Young’s modulus in replicated microcellular materials

Coordination measurements in compacted NaCl irregular powders using X-ray microtomography

On the bulk compressibility of close-packed particles and their composites

Infiltration processing of fibre reinforced composites: governing phenomena

Lorentz-Force-Driven Infiltration By Aluminum

On measuring wettability in infiltration processing

Fracture toughness measurement in fused quartz using triangular chevron-notched micro-cantilevers

Reinforced silver chloride as a model material for the study of dislocations in metal matrix composites

Microsegregation In Cellular Solidification