Publications de Michel Rappaz | EPFL Graph Search

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In order to quantify the cooling conditions undergone by an ingot during direct-chill (DC) casting, thermocouples were immersed in the liquid pool and consequently entrapped in the solid, thus monitoring the temperature of the metal during its descent. Assuming steady-state thermal conditions, the time-dependent temperatures measured by these thermocouples were then converted into spacedependent temperature profiles. These values were the input of a Maximum A Posteriori (MAP) inverse method described by Rap

A fairly simple experimental setup has been designed for testing the resistance of the mushy zone of alloys during solidification under tensile conditions. It has been used to study the effect of coalescence among the solid grains at a late stage of solidi ...

The prediction of the ingot deformation during direct chiil (DC) and electromagnetic (EM) casting of aluminum alloy slabs would allow the optimization of the moldlinductor shape capable of producing flat ingots. The transient thermomechanical model presented here predicts the deformation and the temperature field evolution during DC/EM casting. Deformation in the solid is assumed to obey a viscoplastic law. The model is validated on the basis of the measurements presented in part I. It enables to predict th

The present contribution reviews the recent progress related to the influence of Icosahedral Short-Range Order (ISRO) and icosahedral Quasicrystals (i-QC) formation on the solidification of fcc alloys through minor solute element additions. From intensive ...

Twinned dendrite growth has been found to occur in aluminum alloys when critical thermal conditions (G approximate to 100 K/cm, nu(s) approximate to 1 mm/s) and a slight convection in the melt are present during directional solidification. Split in their t ...

Modelling of hot tearing must encompass several aspects: solidification, percolation of grains, stress/strain development, liquid feeding. The present contribution reviews recent progress made in this domain, both at the macro- and microscopic levels. At t ...

A three-dimensional (3-D) multiphase-field model has been developed in order to study the formation of a micropore constrained to grow in a solid network (i.e. pinching effect). The model accounts for the pressure difference due to capillarity between liqu ...

Hot tearing formation in both a classical tensile test and during direct chill (DC) casting of aluminum alloys has been modeled using a semicoupled, two-phase approach. Following a thermal calculation, the deformation of the mushy solid is computed using a ...

Recently, we have shown that minute Cr additions (typically 0.1 wt%) to Al-Zn alloys solidified in a uniform temperature field lead to the formation of fine equiaxed fcc Al grains [1]. Furthermore, these grains exhibit an unexpectedly large number of twin, ...

Based on detailed EBSD analyses, Kurtuldu et al. (Acta Mater. 70:240-248, 2014) have explained the grain refinement of Au-12.5 wt pctCu-12.5 wt pctAg (yellow gold) by the addition of minute amounts of Ir in terms of icosahedral quasicrystal (iQC)-mediated ...

In order to better understand the microstructure that forms during laser welding of an 18 carat gold and an austenitic stainless steel, solidification of the Au-Fe binary analog has been studied using thermal analysis and interrupted Bridgman experiments. ...

The formation of twinned dendrites (feathery grains) in binary Al-Zn, Al-Mg, Al-Cu and Al-Ni alloys has been studied in specimens directionally solidified under identical thermal conditions, i.e. G approximate to 100 K cm(-1), v approximate to 1 mm s(-1), ...

While studies of solidification microstructures have focused mainly on the tips of the dendrites, the last stage solidification is equally important from the point of view of defect formation (porosity, hot tearing), mechanical strength build-up and precip ...

Intergranular penetration of liquid 18 K gold into a superaustenitic stainless steel, which occurs during laser welding of these two materials, has been studied using a C-ring device which can be put under tensile stresses by a screw. It is shown that liqu ...

The biomedical industry has an increasing demand for processes to join dissimilar metals, such as laser welding of NiTi and stainless steel wires. A region of the weld close to the NiTi interface, which previously was shown to be prone to cracking, was fur ...

Heterogeneous nucleation is governed by the interplay of interfacial energies between a substrate, a solid and a liquid. Although the intensity of these energies can strongly change with the orientation of the nucleus for anisotropic media, this parameter ...

The anisotropy of the solid-liquid interfacial energy plays a key role during the formation of as-solidified microstructures. Using the xi-vector formalism of Cahn and Hoffman, this contribution presents the effect that anisotropy has on the equilibrium sh ...

The prediction of the ingot deformation during direct chill (DC) and electromagnetic (EM) casting of aluminum alloy slabs would allow the optimization of the mold/inductor shape capable of producing flat ingots. The transient thermomechanical model presented here predicts the deformation and the temperature field evolution during DC/EM casting. Deformation in the solid is assumed to obey a viscoplastic law. The model is validated on the basis of the measurements presented in part I. It enables to predict th

As for most of the topics in the field of solidification, Mert Flemings has always pioneered new ideas. While much of the understanding of hot tearing formation was already known about 30 years ago, he devised with Metz an interesting apparatus for studying the resistance of mushy zones to compression and shearing [1,2]. Part of the results of these tests lead Flemings to become interested in semi-solid processing of metallic alloys, with the success we know today (e.g., production of automobile components

The deformation and the temperature field within direct chill (DC) and electromagnetic (EM) cast aluminum ingots have been measured in-situ using a simple experimental set-up. The deformation of the cross section of the cold ingots has also been characterized as a function of the casting speed, alloy composition and inoculation condition. The pull-in of the lateral rolling faces has been found to occur in two sequences for DC cast ingots whereas that associated with EMC was continuous. The pull-in was maxim

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Determination of thermophysical properties and boundary conditions of DC cast aluminum alloys using inverse methods

A new tensile test for aluminum alloys in the mushy state: Experimental method and numerical modeling

Thermomechanical Effects during Direct Chill and Electromagnetic Casting of Aluminum Alloys. Part II : Numerical Simulation

Influence of minor additions on Icosahedral Short-Range Order (ISRO) and its consequences on nucleation and solidification growth kinetics in fcc alloys

Phase Field Modelling Of Twinned Dendrite Growth

Towards a Micro-Macro Model of Hot Tearing

Three-dimensional phase-field simulation of micropore formation during solidification: Morphological analysis and pinching effect

Two-Phase Modeling of Hot Tearing in Aluminum Alloys: Applications of a Semicoupled Method

Probability of twin boundary formation associated with the nucleation of equiaxed grains on icosahedral quasicrystal templates

Influence of Ir Additions and Icosahedral Short Range Order (ISRO) on Nucleation and Growth Kinetics in Au-20.5Wt Pct Cu-4.5Wt PctAg Alloy

Au-Fe alloy solidification and solid-state transformations

Twinned dendrite growth in binary aluminum alloys

Transition of the mushy zone from continuous liquid films to a coherent solid

Intergranular penetration of liquid gold into stainless steel

Three-dimensional chemical analysis of laser-welded NiTi–stainless steel wires using a dual-beam FIB

Influence of anisotropy on heterogeneous nucleation

The influence of solid-liquid interfacial energy anisotropy on equilibrium shapes, nucleation, triple lines and growth morphologies

Thermomechanical Effects during Direct Chill and Electromagnetic Casting of Aluminum Alloys Part II : Numerical Simulation

Study and modeling of hot tearing formation

Experimental investigation of thermomechanical effects during direct chill and electromagnetic casting of aluminium alloys