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SUMMARY:IMX Seminar Series - Crystal plasticity of body-centered cubic tra
 nsition metals at the atomic scale
DTSTART:20230515T131500
DTEND:20230515T141500
DTSTAMP:20260307T133230Z
UID:1fc4b862d28a1c18982e29088b6a4178685078144721768f6778fa53
CATEGORIES:Conferences - Seminars
DESCRIPTION:Dr. Emmanuel Clouet\, SRMP\, CEA\, Univ. Paris-Saclay\, France
 \nPlasticity of crystal materials is mainly controlled by the motion of di
 slocations\, i.e. line defects carrying a shear increment defined by their
  Burgers vector. In transition metals with a body-centered cubic (BCC) cry
 stallographic structure like iron\, tungsten or chromium\, these dislocati
 ons with a 1/2 <111> Burgers vector tend to align along their screw orient
 ation\, the line direction parallel to the Burgers vector. The glide prope
 rties of these screw dislocations are responsible of particular features o
 f plasticity in BCC metals\, among them a strong temperature dependence an
 d deviations from the Schmid law with the yield criterion depending not on
 ly on the resolved shear stress in the slip plane but also on other stress
  components and on their signs. Using atomistic simulations and ab initio 
 calculations\, we show how plasticity in BCC pure metals can be understood
  at low temperature from core properties of screw dislocations\, i.e. from
  the region in the immediate vicinity of the line-defect where the perturb
 ation of the crystal is too high to be described by elasticity and where a
 n atomic description is needed.\nIn presence of impurities like carbon\, a
  strong friction also appears at temperatures high enough to allow for imp
 urity diffusion. Ab initio calculations show that this friction arises fro
 m an attractive interaction of impurities\, in particular C\, with screw d
 islocation\, leading to an important segregation of carbon in the dislocat
 ion core\, even in very pure metals. The dislocation glide motion of screw
  dislocation becomes then controlled by impurity migration. A good agreeme
 nt is obtained between the mechanism deduced from atomic modeling and from
  experimental observations by transmission electron microscopy during in s
 itu tensile tests.\nBio: Emmanuel Clouet is a research director in the phy
 sical metallurgy laboratory at the French Alternative Energies and Atomic 
 Energy Commission (CEA). Before joining CEA in 2004\, Emmanuel was a visit
 ing scientist at the University of Texas at Austin and he received his PhD
  in Physics in 2004 from École Centrale Paris\, France for research perfo
 rmed at CEA and Pechiney (now Constellium). He spent two years on secondme
 nt to Lille University\, France between 2007 and 2009. Emmanuel's research
  focuses on understanding the physical mechanisms controlling microstructu
 re evolution and mechanical properties in metals and alloys used as struct
 ural materials\, with a particular emphasis on crystal plasticity\, irradi
 ation effects and precipitation. His work relies on numerical simulations 
 and modeling ranging from atomic to mesoscopic scale\, in close connection
  with experiments. He received the Jean Rist's award of the French Society
  for Metallurgy and Materials in 2008. He is editor at Acta and Scripta Ma
 terialia.
LOCATION:MXF 1 https://plan.epfl.ch/?room==MXF%201
STATUS:CONFIRMED
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