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Michel Rappaz

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Publications associées (85)

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

Alain Jacot, Jean-Luc Desbiolles, Michel Rappaz, Hossein Meidani

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 ...

Elsevier2012

X-ray tomographic microscopy analysis of the dendrite orientation transition in Al-Zn

Michel Rappaz, Jonathan Friedli, Paolo Di Napoli

Recently, Gonzales and Rappaz [Met. Mat. Trans. A37:2797, 2006] showed the influence of an increasing zinc content on the growth directions of aluminum dendrites. < 100 > and < 110 > dendrites were observed below 25wt.% and above 55wt.% zinc, respectively, ...

Iop Publishing Ltd2012

Phase-field modeling of the dendrite orientation transition in Al-Zn alloys

Michel Rappaz, Jonathan Friedli, Jonathan Dantzig, Paolo Di Napoli

With a few exceptions, phase-field simulations of dendritic growth in cubic materials have been modeled using simple expressions for the interfacial energy anisotropy and with strong anisotropy. However, recent experimental results show that the Dendrite O ...

Iop Publishing Ltd2012

Study of the twinned dendrite tip shape II: Experimental assessment

Michel Rappaz, Marco Cantoni, Pierre Burdet, Mario Alberto Salgado Ordorica

The favorable growth kinetics of twinned dendrites can be explained by their complex morphology, multiple side branching mechanisms, growth undercooling and tip morphology. Three models were proposed for the twinned dendrite tip shape: (i) a grooved tip sa ...

2011

Intergranular penetration of liquid gold into stainless steel

Michel Rappaz, Jean-Daniel Wagnière, Denis Favez, Léa Deillon

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 ...

Elsevier2011

Study of the twinned dendrite tip shape I : Phase-field modeling

Jean-Luc Desbiolles, Michel Rappaz, Mario Alberto Salgado Ordorica

The growth kinetics advantage of twinned aluminum dendrites over regular ones is still an unsolved problem of solidification. Although it is linked to the tip geometry, the influence of a coherent (1 1 1) twin plane on a < 1 1 0 > twinned dendrite tip is u ...

Elsevier2011

Influence of anisotropy on heterogeneous nucleation

Michel Rappaz, Aurèle Mariaux

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 ...

Elsevier2011

Mechanical and microstructural integrity of nickel-titanium and stainless steel laser joined wires

Jean-Marie Drezet, Aïcha Hessler-Wyser, Michel Rappaz, Alireza Karimi, Jonas Vannod

The biomedical industry shows increasing interest in the joining of dissimilar metals, especially with the aim of developing devices that combine different mechanical and corrosive properties. As an example, nickel titanium shape memory alloys joined to st ...

Elsevier2011

Curvature of micropores in Al-Cu alloys: An X-ray tomography study

Michel Rappaz, Milan Felberbaum

Micropores formed in Al-Cu alloys cast under controlled conditions have been analyzed using high-resolution X-ray tomography. The influence of inoculation conditions, copper content, cooling rate and initial hydrogen content on the morphology of pores has ...

Elsevier2011

Effects of Ni additions, trace elements and solidification kinetics on microstructure formation in Sn-0.7Cu solder

Michel Rappaz, Tina Ventura

Five ternary Sn-0.7Cu-xNi alloys with nickel contents in the range 0-1000 ppm have been directionally solidified at different growth rates. The competition between primary tetragonal Sn cells/dendrites, eutectic and primary Cu6Sn5 is interpreted with phase ...

Elsevier2011

Simulation of Semi-Solid Material Mechanical Behavior Using a Combined Discrete/Finite Element Method

Jean-Marie Drezet, Michel Rappaz, André Phillion, Meisam Sistaninia

As a necessary step toward the quantitative prediction of hot tearing defects, a three-dimensional stress–strain simulation based on a combined finite element (FE)/discrete element method (DEM) has been developed that is capable of predicting the mechanica ...

2011

Effective hydrogen diffusion coefficient for solidifying aluminium alloys

Michel Rappaz, Ludger Weber, Milan Felberbaum

An effective hydrogen diffusion coefficient has been calculated for two solidifying Al - 4.5 wt.% Cu and Al - 10 wt.% Cu alloys as a function of the volume fraction of solid. For this purpose, in situ X-ray tomography was performed on these alloys. For eac ...

Elsevier2011

Connectivity of Phases and Growth Mechanisms in Peritectic Alloys Solidified at Low Speed: an X-Ray Tomography Study of Cu-Sn

Michel Rappaz, Jonas Valloton, André Phillion, Marco Stampanoni

The variety of microstructures that form at low solidification speed in peritectic alloys, bands, and islands, or even coupled (or cooperative) growth of the primary alpha and peritectic beta phases, have been previously explained by nucleation-growth mech ...

Springer Verlag2010

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

Michel Rappaz, Jonathan Friedli, Aurèle Mariaux, Mario Alberto Salgado Ordorica

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 ...

Elsevier2010

Au-Fe alloy solidification and solid-state transformations

Michel Rappaz, Jean-Daniel Wagnière

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. ...

Elsevier2010

Characterisation of Laser Welds, between Nitinol and Stainless Steel Wires

Aïcha Hessler-Wyser, Michel Rappaz, Jonas Vannod

Nickel-Titanium (NiTi) shape memory alloys are often used in medical component devices, for instance as guide wires for neurological surgery applications. Manufacturing of such devices becomes more and more challenging, especially considering the need to j ...

2009

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

Michel Rappaz, Vincent Mathier, Stéphane Vernède

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 ...

2009

Micro- and macrosegregation of a peritectic Au-Fe alloy during Bridgman solidification

Michel Rappaz, Denis Favez

In jewelry manufacturing, joining dissimilar materials is usually achieved by soldering or brazing, but these techniques have several disadvantages as compared for example with laser welding. In this last case, however, it is necessary to have a thorough u ...

Minerals, Metals & Materials Soc, 184 Thorn Hill Rd, Warrendale, Pa 15086-7514 Usa2009

In situ X-ray tomography observation of inhomogeneous deformation in semi-solid aluminium alloys

Michel Rappaz, Milan Felberbaum

The aim of this paper is to report the very first in situ observations of the deformation behaviour of an Al-Cu alloy in the semisolid state by using ultrafast, high-resolution X-ray microtomography. It is shown that this deformation is non-homogeneous and ...

2009

Phase Field Modelling Of Twinned Dendrite Growth

Jean-Luc Desbiolles, Michel Rappaz, Mario Alberto Salgado Ordorica

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 ...

Minerals, Metals & Materials Soc, 184 Thorn Hill Rd, Warrendale, Pa 15086-7514 Usa2009

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