D. L. Beke, L. Daroczi, Z. Palanki, University of Debrecen, Debrecen, Hungary; C. Lexcellent, Université de Franche-Comté, Besancon, France
Relations between the equilibrium transformation temperature, To, uniaxial stress, σo, and magnetic field, Bo, are expressed in term of transformation strain, εtr, change in the volume, ΔV, entropy, Ds, and magnetization, ΔM, in the austenite to martensite transformation. Thus, if once one of the above equilibrium transformation parameters (To(0), σo(0), po(0) or Bo(0)) is experimentally determined, then – using the above relations - the others can be easily calculated if εtr, Dsc, ΔV and ΔM are known. Furthermore the external field dependence of the equilibrium parameters can also be given (e.g. To(s)= - (Vεtr/Ds) [σ-o(0)] and σo(T)= - (Ds/Vεtr) [T-To(0)]), where V is the molar volume. The above relations should be strictly valid only if during the stress induced or thermally induced transformations the same types of martensite variants play the determining role. This question will also be addressed by the analysis of available experimental data.
Summary: The relations derived allow, if one of the equilibrium transformation parameters is known, the calculation of the others, using experimentally determined transformation strain, the change in the volume, entropy and magnetization during transformation
