A Quantitative Treatment of the Lattice Softening of Shape Memory Alloys

  • N. Rusović
  • H. Warlimont


The shape memory effect is most commonly observed in β phase alloys which transform martensitically and exhibit the so-called C’ anomaly (1,2). This anomalous elastic behaviour is characterized by the following properties of the elastic shear constant C’ = (C11–C12)/2:
  1. (i)

    its temperature coefficient becomes positive on approaching the equilibrium temperature To from above;

  2. (ii)

    its magnitude decreases with changes in composition which raise To;

  3. (iii)

    its magnitude is of the order of 0.1 ≲ C’ ≲ 0.7 × 1011dynes cm−2(l010 Nm−2), i.e. unusually low, at Ms;

  4. (iv)

    consequently, the elastic anisotropy factor A = C44/C’ is anomalously high, since C44 shows normal behaviour.

In other words the lattice becomes increasingly softer against {llo}<llo> shears as the teperature or composition approaches the instability with respect to a martensitic teansformation. Fig. 1 shoes data of this behavious for a β2-NiAl alliy series which will be treated as an example in this paper.


SHAPE Memory Alloy Shape Memory Effect Fermi Contribution Brillouin Zone Boundary Repulsion Term 
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Copyright information

© Springer Science+Business Media New York  1975

Authors and Affiliations

  • N. Rusović
    • 1
  • H. Warlimont
    • 1
  1. 1.Max-Planck-Institut für MetallforschungWest-Germany

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