Version 1
: Received: 29 July 2024 / Approved: 30 July 2024 / Online: 30 July 2024 (10:37:47 CEST)
How to cite:
Beke, D. L.; Azim, A. A. On the Strong Composition Dependence of the Martensitic Transformation Temperature and Heat in Shape Memory Alloys. Preprints2024, 2024072446. https://doi.org/10.20944/preprints202407.2446.v1
Beke, D. L.; Azim, A. A. On the Strong Composition Dependence of the Martensitic Transformation Temperature and Heat in Shape Memory Alloys. Preprints 2024, 2024072446. https://doi.org/10.20944/preprints202407.2446.v1
Beke, D. L.; Azim, A. A. On the Strong Composition Dependence of the Martensitic Transformation Temperature and Heat in Shape Memory Alloys. Preprints2024, 2024072446. https://doi.org/10.20944/preprints202407.2446.v1
APA Style
Beke, D. L., & Azim, A. A. (2024). On the Strong Composition Dependence of the Martensitic Transformation Temperature and Heat in Shape Memory Alloys. Preprints. https://doi.org/10.20944/preprints202407.2446.v1
Chicago/Turabian Style
Beke, D. L. and Asmaa A. Azim. 2024 "On the Strong Composition Dependence of the Martensitic Transformation Temperature and Heat in Shape Memory Alloys" Preprints. https://doi.org/10.20944/preprints202407.2446.v1
Abstract
General derivation of the well-known Ren-Otsuka relation, 1/α (dTo)/dx=-α/β (where To, x, α and β(>0) are the transformation temperature, the composition, as well as the composition and temperature coefficient of the critical shear constant, c’, respectively) for shape memory alloys, SMAs, is provided based on the similarity of interatomic potentials in the framework of dimensional analysis. A new dimensionless variable, to(x)=(To (x))/(Tm (x) ), describing the phonon softening (where Tm is the melting point) is introduced. The dimensionless values of the heat of transformation, H, and entropy, S as well as the elastic constants c’, c44, A=c44/c' are universal functions of to(x) and have the same constant values at to(0) within sub-classes of host SMAs having the same type of crystal symmetry change during martensitic transformation. The ratio of (dto)/dx and α has the same constant value for all members of a given sub-class and relative increase of c’ with increasing composition should be compensated by the same decrease of to. In the generalized Ren-Otsuka relation the anisotropy factor, A appears instead of c’ and α as well as β are the differences of the corresponding coefficients for the c44 and c’ elastic constants. The obtained linear relation between h and to rationalizes the observed empirical linear relations between the heat of transformation measured by DSC (QAM) and the martensite start temperature, Ms.
Keywords
shape memory alloys; martensitic transformation; phonon softening; transformation temperature; heat and entropy; martensite start temperature
Subject
Physical Sciences, Chemical Physics
Copyright:
This is an open access article distributed under the Creative Commons Attribution License which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.
