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SUMMARY:Quantitative Prediction of Solute Strengthening in Metal Alloys - 
 Professor William Curtin\, École polytechnique fédérale de Lausanne EPF
 L
DTSTART:20141024T133000Z
DTEND:20141024T150000Z
UID:TALK54795@talks.cam.ac.uk
CONTACT:Ms Helen Gardner
DESCRIPTION:Alloys containing substitutional solutes exhibit strengthening
  due to favorable solute fluctuations within the alloy that hinder disloca
 tion motion. Here\, a quantitative\, parameter free model to predict the f
 low stress as a function of temperature and strain rate of such alloys is 
 presented.1\,2  The model is related to early models and concepts but rect
 ifies the many limitations of earlier works.  The only inputs to the model
  are the solute/dislocation interaction energies in and around the disloca
 tion core\, which are computed using density functional theory within a fl
 exible-boundary-condition method.  The model then predicts the zero temper
 ature flow stress and energy barrier for dislocation motion\, and standard
  thermal activation theory then leads to the prediction of finite temperat
 ure/strain-rate flow stresses.  The model is used to predict the flow stre
 sses of various Al alloys and excellent results are obtained.  The model i
 s then used directly to predict basal strengthening in Mg-Al and Mg-Zn.3  
 Due to the different dislocation core structure\, the model predicts a tra
 nsition from flow controlled by short-range solutes to flow controlled by 
 long-range solutes with increasing temperature and predictions agree well 
 with experiments.  The model is then applied to twinning in Mg\, and yet n
 ew features emerge along with quantitatively accurate predictions.  Finall
 y\, we discuss how the model is being extended to predict strengthening in
  new “high entropy” alloys\, which are non-dilute\, multi-component sy
 stems having fcc structure with random solute distributions (e.g. FeNiCoCr
 Mn).  Overall\, this parameter-free model using first-principles input thu
 s provides a basis for achieving the long-sought goal of computational des
 ign of alloys\, within the context of solute-strengthening mechanisms. \n1
 .	G. P. Leyson\, W. A. Curtin\, L. G. Hector Jr.\, and  C. Woodward\, “Q
 uantitative prediction of solute strengthening in aluminium alloys”\, Na
 ture Materials 9\, 750-755 (2010).\n2.	G. Leyson\, L. G. Hector\, and W. A
 . Curtin\, “Solute strengthening from first principles and application t
 o aluminum alloys”\, Acta Mater. 60\, 3873-3884 (2012).\n3.	G. P. M. Ley
 son\, L. G. Hector\, and W. A. Curtin\, “First-Principles prediction of 
 yield stress for basal slip in Mg-Al alloys”\, Acta Mater. 60\, 5197-520
 3 (2012).
LOCATION: Cambridge University Engineering Department\, LR4
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