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SUMMARY:Exploding\, weeping and reversible phase transformations in cerami
 cs - Prof Richard James\, Distinguished McKnight University Professor\, De
 partment of Aerospace and Engineering Mechanics\, University of Minnesota
DTSTART:20220211T140000Z
DTEND:20220211T150000Z
UID:TALK167684@talks.cam.ac.uk
CONTACT:Hilde Hambro
DESCRIPTION:The systematic tuning of the lattice parameters to achieve imp
 roved kinematic compatibility between phases is a broadly effective strate
 gy for improving the reversibility\, and lowering the hysteresis\, of soli
 d-solid phase transformations.  Thus\, it came as a big surprise\, in join
 t work with Eckhard Quandt and his group in Kiel\, that our attempt to use
  these methods to guide the search for a shape memory ceramic led not to a
  high degree of reversibility\, but rather to violently explosive or “we
 eping” behavior (i.e.\, gradual falling apart at the grain boundaries) i
 n oxides of ZrHfYNb. In the lecture I will review the theory of supercompa
 tibility and its applications\, and then turn to the puzzle of ZrHfYNb.  S
 everal aspects of this system are unusual -- multiple transformation corre
 spondences (also seen in TiNi) and unusual symmetries – and we analyze t
 he behavior in light of these features.  Overall\, our results show a dive
 rsity of behavior\, from reversible to explosive\, is possible in a chemic
 ally homogeneous system by slight manipulation of conditions of compatibil
 ity.
LOCATION:CUED LR4
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