Twinning hierarchy, shape memory, and superelasticity demonstrated by molecular dynamics

M. Zelazny, R. Richardson, Graeme Ackland

Research output: Contribution to journalArticlepeer-review

Abstract

A martensitic phase transition exhibiting shape memory, transformation-induced plasticity, or superelasticity typically involves a transformation between a high temperature, high symmetry phase and a low temperature, low symmetry phase. There have been numerous attempts using molecular dynamics to simulate the shape memory behavior, where the memory is stored in a twinned martensite and deformation occurs by motion of twin boundaries. However, the 3D case has always proved elusive, because suitable interatomic potentials to produce a unique low temperature phase are difficult to obtain. Here we present a study in which the binary Morse potential is tuned specifically to maximize the difference between L1(0) and B19 (Strukturbericht notation, spacegroups P4/mmm and Pmma) structures. The twinned structure of martensite has been induced by gradually cooling the sample below the transition temperature. A bar-shaped sample was plastically deformed in the martensite phase, and on reheating above the transition temperature the initial shape was recovered. The effect of the shear-induced phase transition on the nanostructure of resulting martensite has also been investigated. An unusual discovery is that of a hierarchy of twins: nanotwins accommodate the mismatch between austenite and martensite at the habit plane, while dynamically created macrotwins are responsible for the deformation behavior and shape memory.

Original languageEnglish
Article number144113
Pages (from-to)-
Number of pages7
JournalPhysical review B: Condensed matter and materials physics
Volume84
Issue number14
DOIs
Publication statusPublished - 18 Oct 2011

Keywords

  • MARTENSITIC PHASE-TRANSFORMATIONS
  • CRYSTAL-STRUCTURE
  • NIAL ALLOY
  • SIMULATION
  • TRANSITION
  • ZIRCONIUM
  • MICROSTRUCTURE
  • POTENTIALS
  • AUSTENITE
  • STABILITY

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