skip to main content

SciTech ConnectSciTech Connect

Title: Influence of volume magnetostriction on the thermodynamic properties of Ni-Mn-Ga shape memory alloys

In the present article, the thermodynamic properties of Ni-Mn-Ga ferromagnetic shape memory alloys exhibiting the martensitic transformations (MTs) above and below Curie temperature are compared. It is shown that when MT goes below Curie temperature, the elastic and thermal properties of alloy noticeably depend on magnetization value due to spontaneous volume magnetostriction. However, the separation of magnetic parts from the basic characteristics of MT is a difficult task, because the volume magnetostriction does not qualitatively change the transformational behaviour of alloy. This problem is solved for several Ni-Mn-Ga alloys by means of the quantitative theoretical analysis of experimental data obtained in the course of stress-strain tests. For each alloy, the entropy change and the transformation heat evolved in the course of MT are evaluated, first, from the results of stress-strain tests and, second, from differential scanning calorimetry data. For all alloys, a quantitative agreement between the values obtained in two different ways is observed. It is shown that the magnetic part of transformation heat exceeds the non-magnetic one for the Ni-Mn-Ga alloys undergoing MTs in ferromagnetic state, while the elevated values of transformation heat measured for the alloys undergoing MTs in paramagnetic state are caused by large MT strains.
Authors:
 [1] ;  [2] ;  [2] ;  [3] ;  [2] ;  [4] ;  [5]
  1. National University of Science and Technology “MISiS,” Moscow 119049 (Russian Federation)
  2. (Ukraine)
  3. Institute of Magnetism, 36-b, Vernadsky Str., Kyiv 03142 (Ukraine)
  4. (Spain)
  5. Departament de Fisica, Universitat de les Illes Balears, Ctra. de Valldemossa, km 7.5, 07122 Palma de Mallorca (Spain)
Publication Date:
OSTI Identifier:
22492770
Resource Type:
Journal Article
Resource Relation:
Journal Name: Journal of Applied Physics; Journal Volume: 118; Journal Issue: 13; Other Information: (c) 2015 AIP Publishing LLC; Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSICS; ALLOYS; CALORIMETRY; CURIE POINT; ENTROPY; MAGNETIZATION; MAGNETOSTRICTION; PHASE TRANSFORMATIONS; SHAPE MEMORY EFFECT; STRAINS; STRESSES