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PMMH’s weekly seminar is held every Friday at 11 am (map)
Stéphane Perrard
Etienne Reyssat
Virgile Thiévenaz
PMMH
BARRE CASSAN
BAT A 1ER ETAGE CASE 18
7 QUAI SAINT BERNARD
75005 PARIS
France
Tel : (33) 1 40 79 45 22
Séminaire PMMH - Christophe Denoual, CEA
A path to model complex displacive transitions
C. Denoual1,2, N. Bruzy1,2
1-CEA, DAM, DIF, F-91297 Arpajon, France
2-Université Paris-Saclay, LMCE, F-91680 Bruyères-le-Châtel, France
Under shock loading, crystalline metals can accommodate stresses through very rapid microstructural transitions such as deformation twinning or martensitic phase transitions. These transformations occur via a collective movement of atoms (referred to as a "military" transition), typically resulting in a microstructure composed of long lamellae aligned along specific planes known as habit planes. The very limited number of crystallographic orientations observed during these transitions (e.g., 12 for twinning under shock in tantalum) arises from the limited number of possible deformation paths associated with these transitions (6 for tantalum twinning). Since these transitions lead to another well-defined crystalline structure, successive deformations can interlock, creating microstructures of remarkable complexity.
In this presentation, we will demonstrate that modeling such a transition can be achieved through a "reaction pathway graph" that represents the first n minimal-energy pathways connecting one stable phase to another. Several examples illustrating the richness of this approach will be discussed, particularly in the context of tantalum twinning under rapid loading conditions. In that case, deformation twinning is in competition with plasticity through the motion of dislocations, emphasizing the need for a detailed coupling between the graph of reaction pathways and crystal plasticity description.
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Séminaire PMMH - Vince Craig, Australian National University, Australia
Vendredi 11 juillet de 11h00 à 12h00 - Salle réunion PMMH 1
Underscreening Stable colloidal systems at very high electrolyte concentrations
In colloidal systems the range and strength of electrostatic interactions has a profound effect on a range of properties including the stability of colloidal dispersions and the phase behaviour of surfactant and polymer systems. The Debye length has proven to be a very effective measure of the range of (…)
The audience is composed of people with rather heterogeneous backgrounds including specialists in solids, fluids, granular flows, statistical physics... so the idea is to keep your talk understandable by people not necessarily working in your field... The seminar time slot runs from 11am to noon so the best is to make the talk last around 45 minutes to leave some time for discussion.
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Link to cofee seminar (internal, every Thursday)
