DOI QR코드

DOI QR Code

Identification of crystal variants in shape-memory alloys using molecular dynamics simulations

  • Wu, Jo-Fan (Department of Civil Engineering, National Taiwan University) ;
  • Yang, Chia-Wei (Department of Materials Science and Engineering, National Chiao Tung University) ;
  • Tsou, Nien-Ti (Department of Materials Science and Engineering, National Chiao Tung University) ;
  • Chen, Chuin-Shan (Department of Civil Engineering, National Taiwan University)
  • Received : 2016.05.04
  • Accepted : 2016.07.12
  • Published : 2017.03.25

Abstract

Shape-memory alloys (SMA) have interesting behaviors and important mechanical properties due to the solid-solid phase transformation. These phenomena are dominated by the evolution of microstructures. In recent years, the microstructures in SMAs have been studied extensively and modeled using molecular dynamics (MD) simulations. However, it remains difficult to identify the crystal variants in the simulation results, which consist of large numbers of atoms. In the present work, a method is developed to identify the austenite phase and the monoclinic martensite crystal variants in MD results. The transformation matrix of each lattice is calculated to determine the corresponding crystal variant. Evolution of the volume fraction of the crystal variants and the microstructure in Ni-Ti SMAs under thermal and mechanical boundary conditions are examined. The method is validated by comparing MD-simulated interface normals with theoretical solutions. In addition, the results show that, in certain cases, the interatomic potential used in the current study leads to inconsistent monoclinic lattices compared with crystallographic theory. Thus, a specific modification is applied and the applicability of the potential is discussed.

Keywords

Acknowledgement

Supported by : Ministry of Science and Technology (MOST)

References

  1. Bhattacharya, K. (2003), "Microstructure of martensite: Why it forms and how it gives rise to the shapememory effect", Oxford University Press.
  2. Chadwick, P. (2012), "Continuum mechanics: Concise theory and problems", Courier Corporation.
  3. Eriksen, J. (1984), "The cauchy and born hypothesis for crystals", Phase Transformations and Material Instabilities in Solids, Academic Press.
  4. Finnis, M.W. and Sinclair, J.E. (1984), "A simple empirical N-body potential for transition-metals", Philos. Mag. a-Phys. Condens. Matt. Struct. Defect. Mech. Propert., 50(1), 45-55.
  5. Hane, K.F. and Shield, T. (1999), "Microstructure in the cubic to monoclinic transition in titanium-nickel shape memory alloys", Acta Mater., 47(9), 2603-2617. https://doi.org/10.1016/S1359-6454(99)00143-3
  6. Hane, K.F. and Shield, T.W. (1998), "Symmetry and microstructure in martensites", Philos. Mag. A, 78(6), 1215-1252. https://doi.org/10.1080/01418619808239984
  7. Kastner, O., Eggeler, G., Weiss, W. and Ackland, G.J. (2011), "Molecular dynamics simulation study of microstructure evolution during cyclic martensitic transformations", J. Mech. Phys. Sol., 59(9), 1888-1908. https://doi.org/10.1016/j.jmps.2011.05.009
  8. Knowles, K.M. and Smith, D.A. (1981), "The crystallography of the martensitic-transformation in equiatomic nickel-titanium", Acta Metall., 29(1), 101-110. https://doi.org/10.1016/0001-6160(81)90091-2
  9. Lai, W.S. and Liu, B.X. (2000), "Lattice stability of some Ni-Ti alloy phases versus their chemical composition and disordering", J. Phys. Condens. Matt., 12(5), L53-L60. https://doi.org/10.1088/0953-8984/12/5/101
  10. Mirzaeifar, R., Gall, K., Zhu, T., Yavari, A. and DesRoches, R. (2014), "Structural transformations in NiTi shape memory alloy nanowires", J. Appl. Phys., 115(19), 194307. https://doi.org/10.1063/1.4876715
  11. Saitoh, K.I., Sato, T. and Shinke, N. (2006), "Atomic dynamics and energetics of martensitic transformation in nickel-titanium shape memory alloy", Mater. Trans., 47(3), 742-749. https://doi.org/10.2320/matertrans.47.742
  12. Sato, T., Saitoh, K.I. and Shinke, N. (2006), "Molecular dynamics study on microscopic mechanism for phase transformation of Ni-Ti alloy", Model. Simulat. Mater. Sci. Eng., 14(5), S39. https://doi.org/10.1088/0965-0393/14/5/S05
  13. Shimizu, F., Ogata, S. and Li, J. (2007), "Theory of shear banding in metallic glasses and molecular dynamics calculations", Mater. Trans., 48(11), 2923-2927. https://doi.org/10.2320/matertrans.MJ200769
  14. Yang, L. and Dayal, K. (2010), "Formulation of phase-field energies for microstructure in complex crystal structures", Appl. Phys. Lett., 96(8), 081916. https://doi.org/10.1063/1.3319503
  15. Zhong, Y. and Zhu, T. (2014), "Phase-field modeling of martensitic microstructure in NiTi shape memory alloys", Acta Mater., 75, 337-347. https://doi.org/10.1016/j.actamat.2014.04.013
  16. Zhong, Y., Gall, K. and Zhu, T. (2011), "Atomistic study of nanotwins in NiTi shape memory alloys", J. Appl. Phys., 110(3), 033532. https://doi.org/10.1063/1.3621429
  17. Zhong, Y., Gall, K. and Zhu, T. (2012), "Atomistic characterization of pseudoelasticity and shape memory in NiTi nanopillars", Acta Mater., 60(18), 6301-6311. https://doi.org/10.1016/j.actamat.2012.08.004