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Michel Rappaz

Cette personne a quitté l’EPFL

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Publications associées (85)

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Application of single pan thermal analysis to Cu-Sn peritectic alloys

Michel Rappaz, Thomas Campanella

Single pan thermal analyses (SPTA) have been performed on Cu–14.5 wt.% Sn, Cu–21.3 wt.% Sn and Cu–26.8 wt.% Sn peritectic alloys. For this purpose, a SPTA assembly has been built and calibrated. As the latent heat is a function of temperature and compositi ...

Elsevier2008

Characterisation of Laser Welds, between Nitinol and Stainless Steel Wires

Michel Rappaz, Aïcha Hessler-Wyser, 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

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

Michel Rappaz, Jean-Marie Drezet, 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

Modeling and characterization of grain structures and defects in solidification

Michel Rappaz

The paper by Karma and Tourret (this volume) in this special issue focuses on multiscale modeling approaches ranging from atoms to microstructure. In the present one, the most recent and significant modeling contributions dealing with the scale of solidifi ...

Elsevier2016

Dendritic Growth Morphologies in Al-Zn Alloys-Part I: X-ray Tomographic Microscopy

Michel Rappaz, Paolo Di Napoli, Jonathan Friedli

Upon solidification, most metallic alloys form dendritic structures that grow along directions corresponding to low index crystal axes, e.g., directions in fcc aluminum. However, recent findings[1,2] have shown that an increase in the zinc content in Al-Zn ...

Springer Verlag2013

Influence of Minor Cr-Additions to the Growth of Columnar Dendrites in Al-Zn Alloys: Influence of Icosahedral Short Range Order in the Liquid

Michel Rappaz, Güven Kurtuldu

The effect of minute Cr additions on dendritic growth directions in Al-20 wt pct Zn alloy has been investigated. As first evidenced by Gonzales and Rappaz (Metall Mater Trans A 37:2797-2806, 2006) Al-Zn alloys exhibit a Dendrite Orientation Transition (DOT ...

SPRINGER2020

Influence of icosahedral short range order on diffusion in liquids: A study on Al-Zn-Cr alloys

Michel Rappaz, Güven Kurtuldu

It has been shown recently that minute additions of Cr in Al-Zn alloys refine the solidified grain structure and induce multiply-twinned grains which can only be explained if the icosahedral symmetry is considered (Kurtuldu et al., 2013). It has been sugge ...

Elsevier2016

Thermodynamic Aspects of Homogeneous Nucleation Enhanced by Icosahedral Short Range Order in Liquid Fcc-Type Alloys

Michel Rappaz, Güven Kurtuldu

We have recently shown that minute solute element additions to liquid metallic alloys can strongly influence the nucleation of the fcc phase and act as a grain refinement method. Electron back-scattered diffraction observations revealed a concomitant incre ...

Springer2015

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

Michel Rappaz, Vincent Mathier

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 ...

2008

Time-Resolved X-Ray Microtomography Observation of Intermetallic Formation Between Solid Fe and Liquid Al

Michel Rappaz, Cécile Hébert, Aïcha Hessler-Wyser, Guillaume Pasche

Time-resolved in situ X-ray tomography combined with scanning electron microscopy was performed on an Al-Fe diffusion system at 973 K (700 A degrees C) to study the formation of the main intermetallic compounds occurring at the interface. After nucleation ...

Springer US2013

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

Michel Rappaz

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 ...

IOP PUBLISHING LTD2019

Phase Field Modelling Of Twinned Dendrite Growth

Michel Rappaz, Jean-Luc Desbiolles

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

Towards a Micro-Macro Model of Hot Tearing

Michel Rappaz, Jean-Marie Drezet, Stéphane Vernède, Vincent Mathier

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 ...

Trans Tech Publications2006

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

Michel Rappaz, Alain Jacot, Jean-Luc Desbiolles, 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

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

Michel Rappaz, Stéphane Vernède, Vincent Mathier

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

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

Michel Rappaz, Güven Kurtuldu

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, ...

Iop Publishing Ltd2015

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

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

Michel Rappaz

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 ...

SPRINGER2019

Twinned dendrite growth in binary aluminum alloys

Michel Rappaz

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), ...

Elsevier2008

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

Michel Rappaz, Stéphane Vernède

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 ...

2006