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Title: Experimental evidence of stress-field-induced selection of variants in Ni-Mn-Ga ferromagnetic shape-memory alloys

Abstract

The in situ time-of-flight neutron-diffraction measurements captured well the martensitic transformation behavior of the Ni-Mn-Ga ferromagnetic shape-memory alloys under uniaxial stress fields. We found that a small uniaxial stress applied during phase transformation dramatically disturbed the distribution of variants in the product phase. The observed changes in the distributions of variants may be explained by considering the role of the minimum distortion energy of the Bain transformation in the effective partition among the variants belonging to the same orientation of parent phase. It was also found that transformation kinetics under various stress fields follows the scale law. The present investigations provide the fundamental approach for scaling the evolution of microstructures in martensitic transitions, which is of general interest to the condensed matter community.

Authors:
 [1];  [2];  [3]; ; ;  [1]; ;  [4]
  1. Department of Materials Science and Engineering, University of Tennessee, Knoxville, Tennessee 37996 (United States)
  2. (Ministry of Education), Northeastern University, Shenyang 110004 (China)
  3. Los Alamos Neutron Scattering Center, Los Alamos National Laboratory, New Mexico 87545 (United States)
  4. Key Laboratory for Anisotropy and Texture of Materials (Ministry of Education), Northeastern University, Shenyang 110004 (China)
Publication Date:
OSTI Identifier:
20957833
Resource Type:
Journal Article
Resource Relation:
Journal Name: Physical Review. B, Condensed Matter and Materials Physics; Journal Volume: 75; Journal Issue: 17; Other Information: DOI: 10.1103/PhysRevB.75.174404; (c) 2007 The American Physical Society; Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND SUPERFLUIDITY; CRYSTAL STRUCTURE; FERROMAGNETIC MATERIALS; GALLIUM ALLOYS; MANGANESE ALLOYS; MICROSTRUCTURE; NEUTRON DIFFRACTION; NICKEL ALLOYS; PHASE TRANSFORMATIONS; SHAPE MEMORY EFFECT; STRESSES; TIME-OF-FLIGHT METHOD; TRANSFORMATIONS

Citation Formats

Wang, Y. D., Key Laboratory for Anisotropy and Texture of Materials, Brown, D. W., Choo, H., Liaw, P. K., Benson, M. L., Cong, D. Y., and Zuo, L. Experimental evidence of stress-field-induced selection of variants in Ni-Mn-Ga ferromagnetic shape-memory alloys. United States: N. p., 2007. Web. doi:10.1103/PHYSREVB.75.174404.
Wang, Y. D., Key Laboratory for Anisotropy and Texture of Materials, Brown, D. W., Choo, H., Liaw, P. K., Benson, M. L., Cong, D. Y., & Zuo, L. Experimental evidence of stress-field-induced selection of variants in Ni-Mn-Ga ferromagnetic shape-memory alloys. United States. doi:10.1103/PHYSREVB.75.174404.
Wang, Y. D., Key Laboratory for Anisotropy and Texture of Materials, Brown, D. W., Choo, H., Liaw, P. K., Benson, M. L., Cong, D. Y., and Zuo, L. Tue . "Experimental evidence of stress-field-induced selection of variants in Ni-Mn-Ga ferromagnetic shape-memory alloys". United States. doi:10.1103/PHYSREVB.75.174404.
@article{osti_20957833,
title = {Experimental evidence of stress-field-induced selection of variants in Ni-Mn-Ga ferromagnetic shape-memory alloys},
author = {Wang, Y. D. and Key Laboratory for Anisotropy and Texture of Materials and Brown, D. W. and Choo, H. and Liaw, P. K. and Benson, M. L. and Cong, D. Y. and Zuo, L.},
abstractNote = {The in situ time-of-flight neutron-diffraction measurements captured well the martensitic transformation behavior of the Ni-Mn-Ga ferromagnetic shape-memory alloys under uniaxial stress fields. We found that a small uniaxial stress applied during phase transformation dramatically disturbed the distribution of variants in the product phase. The observed changes in the distributions of variants may be explained by considering the role of the minimum distortion energy of the Bain transformation in the effective partition among the variants belonging to the same orientation of parent phase. It was also found that transformation kinetics under various stress fields follows the scale law. The present investigations provide the fundamental approach for scaling the evolution of microstructures in martensitic transitions, which is of general interest to the condensed matter community.},
doi = {10.1103/PHYSREVB.75.174404},
journal = {Physical Review. B, Condensed Matter and Materials Physics},
number = 17,
volume = 75,
place = {United States},
year = {Tue May 01 00:00:00 EDT 2007},
month = {Tue May 01 00:00:00 EDT 2007}
}
  • In situ time-of-flight neutron diffraction and high-energy x-ray diffraction techniques were used to reveal the preferred reselection of martensite variants through a detwinning process in polycrystalline Ni-Mn-Ga ferromagnetic shape memory alloys under uniaxial compressive stress. The variant reorientation via detwinning during loading can be explained by considering the influence of external stress on the grain/variant orientation-dependent distortion energy. These direct observations of detwinning provide a good understanding of the deformation mechanisms in shape memory alloys.
  • The Ferromagnetic Heusler alloy Ni{sub 2}MnGa is known to undergo a structural phase transformation of martensitic type. Thermoelastic nature, shape memory effect (SME) and superelasticity were sound to be intrinsic to this transformation. In this work the authors present the results of the investigation of the following problems: how M{sub s}, the thermal hysteresis, Curie temperature, transformation heat are affected by the composition variation in the Ni-Mn-Ga alloy system in a concentration interval for each component of about 10 at. %. This work was performed to make sure that the new family of Ni-Mn-Ga based shape memory alloys (SMA) withmore » a wide variety of structural and magnetic properties is actually elaborated.« less
  • The effect of Co addition on crystal structure, martensitic transformation, Curie temperature and compressive properties of Ni{sub 53-x}Mn{sub 25}Ga{sub 22}Co{sub x} alloys with the Co content up to 14 at% was investigated. An abrupt decrease of martensitic transformation temperature was observed when the Co content exceeded 6 at.%, which can be attributed to the atomic disorder resulting from the Co addition. Substitution of Co for Ni proved efficient in increasing the Curie temperature. Compression experiments showed that the substitution of 4 at.% Co for Ni did not change the fracture strain, but lead to the increase in the compressive strengthmore » and the decrease in the yield stress. This study may offer experimental data for developing high performance ferromagnetic shape memory alloys.« less
  • Vacancies control any atomic ordering process and consequently most of the order-dependent properties of the martensitic transformation in ferromagnetic shape memory alloys. Positron annihilation spectroscopy demonstrates to be a powerful technique to study vacancies in NiMnGa alloys quenched from different temperatures and subjected to post-quench isothermal annealing treatments. Considering an effective vacancy type the temperature dependence of the vacancy concentration has been evaluated. Samples quenched from 1173 K show a vacancy concentration of 1100 ± 200 ppm. The vacancy migration and formation energies have been estimated to be 0.55 ± 0.05 eV and 0.90 ± 0.07 eV, respectively.
  • The magnetoelasticity and magnetoplasticity behaviors of a Ni-Co-Mn-In ferromagnetic shape memory alloy (FSMA) induced by the reverse phase transformation interplayed under multiple (temperature, magnetic, and stress) fields were captured directly by high-energy synchrotron x-ray diffraction technique. The experiments showed the direct experimental evidence of that a stress ({approx}50 MPa) applied to this material made a complete recovery of the original orientations of the martensite variants, showing a full shape memory effect. This finding offers the in-depth understanding the fundamental properties and applications of the Ni-Co-Mn-In FSMA with the magnetic-field-induced reverse transformation.