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SUMMARY:Simulations for Quantifying Dislocation Behavior and Strengthening
  in Metallic Alloys 
DTSTART:20131108T141500
DTEND:20131108T151500
DTSTAMP:20260407T183806Z
UID:84af938ad379cb9d8ce9ccfadcc476ebb526ae420cb2021ad5d0cf49
CATEGORIES:Conferences - Seminars
DESCRIPTION:Dr. Satish I Rao\, UES Inc.\, Dayton\, USA\nBio : Dr.Satish I 
 Rao obtained his doctoral degree in Materials Science and Engineering from
  Virginia Tech in 1984. He was a Research Assistant Professor at Virginia 
 Tech till 1990. He joined Wright Patterson Air Force Base as a National Re
 search Council Post-Doctoral fellow in 1990. He joined UES Inc. in 1992 as
  a Materials Research Scientist. He is now a Senior Research Scientist at 
 UES Inc. He has more than 20 years of experience researching in the comput
 ational materials science area\, working as an on-site research contractor
  for UES Inc.\, at Wright-Patterson Air Force Base. His areas of expertise
  include 3D atomistic simulations (molecular statics and molecular dynamic
 s) and 3D dislocation dynamics simulations of dislocation behavior in high
  temperature materials of interest to the Department of Defense such as me
 tals\, intermetallics and their alloys. Specific materials of expertise in
 clude Ni\, Cu\, Ti\, NiAl\, Ni3Al\, TiAl\, Superalloys\, Refractory metals
 \, Silicides\, Metallic multilayers\, Metallic nano and micropillars. He h
 as extensive experience in modeling the mechanical behavior of structural 
 materials including  Peierl’s lattice resistance\, solid solution stren
 gthening\, precipitation strengthening\, interface strengthening\, creep a
 nd fatigue.\nAbstract : Large-scale atomistic and discrete dislocation dyn
 amics simulations are useful tools for quantifying dislocation behavior an
 d strengthening in metallic alloys. Three examples illustrate  use of the
 se techniques: a) 2D discrete dislocation dynamics simulations of precipit
 ation hardening in 2-phase superalloys\, b) 3D dislocation dynamics simula
 tions of the size-affected mechanical response of micrometer-scale FCC\, a
 s well as two-phase superalloy crystals and c) molecular dynamics simulati
 ons of the intrinsic Peierls lattice resistance for <a> type screw disloca
 tions in hcp α-Ti oriented for prism and basal slip. In the first example
 \, discrete dislocation simulations show the effects of size\, shape\, vol
 ume fraction of precipitates\, APB energy and coherency stresses on the cr
 itical stress for a pair of gliding dislocations to defeat the obstacles e
 ither by cutting or bowing. The results are used to develop a simple to us
 e spreadsheet model that predicts the yield behavior of 2-phase superalloy
 s. In the second example\, large-scale 3D dislocation dynamics simulations
  are used to show that two size-sensitive athermal hardening mechanisms\, 
 beyond forest and precipitation hardening\, are sufficient to develop the 
 dimensional scaling of the flow stress\, stochastic stress variation\, flo
 w intermittency and\, high initial strain-hardening rates\, similar to exp
 erimental observations for various metallic micropillars.  These two mech
 anisms are called source-truncation hardening and exhaustion hardening.  
 In the third example\, molecular dynamics simulations are used to develop 
 a strain-rate sensitive kink-pair model for the motion of  <a> type screw
  dislocations on the prism\, basal planes in α-Ti at low temperatures. 
   The model is shown to be in reasonable agreement with the low temperatu
 re yield behavior of single crystal α-Ti oriented for prism\, basal slip.
   Finally\, current work that uses large-scale atomistic simulations for 
 deriving physically-based thermally-activated cross-slip rules for input i
 nto 3D dislocation dynamics code  that enables studying strain-rate and t
 emperature effects on the mechanical behavior of micropillars\, is discuss
 ed.
LOCATION:ME B3 31 http://plan.epfl.ch/?room=MEB331
STATUS:CONFIRMED
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