MSA  Vol.10 No.8 , August 2019
A Molecular Dynamics Study on the Effects of Lattice Defects on the Phase Transformation from BCC to FCC Structures
Abstract: Molecular dynamics simulations of the phase transformation from body- centered-cubic (bcc) to face-centered-cubic (fcc) structures were performed. A Morse-type function was applied, and the parameters were determined so that both fcc and bcc structures were stable for the perfectcrystal model. When the fcc structure was superior to the bcc structure, the bcc model transformed to fcc. Two mechanisms, based on the Bain and Nishiyama- Wasserman (NW) relationships, were considered. Then, point or linear lattice defects, i.e., randomly scattered or regularly aligned vacancies, were introduced. Consequently, bcc models tended to transform to an fcc structure, whereas fcc models remained stable. The transformation process was also investigated in detail. BCC-to-FCC transformation is often considered as a homogeneous process based on changes in the axis lengths, and such a process was observed for the perfectcrystal model. Conversely, for the defect models, local heterogeneous deformation patterns, including cylindrical domain and planar interface formation, were observed. These behaviors are considered to be related to plastic deformation during phase transformation, and the validity of the presented model for further investigation was confirmed.
Cite this paper: Uehara, T. (2019) A Molecular Dynamics Study on the Effects of Lattice Defects on the Phase Transformation from BCC to FCC Structures. Materials Sciences and Applications, 10, 543-557. doi: 10.4236/msa.2019.108039.

[1]   Bhadeshia, H.K.D.H. and honeycombe, R.W.K. (2017) Steels—Microstructure and properties. 4th Edition, Butterworth-Heinemann, Oxford.

[2]   Greenwood, G.W. and Johnson, R.H. (1965) The Deformation of Metals under Small Stresses during Phase Transformations. Proceedings of the Royal Society of London. Series A, 283, 403-422.

[3]   Leblond, J.B., Devaux, J. and Devaux, J.C. (1989) Mathematical Modelling of Transformation Plasticity in Steels I: Case of Ideal-Plastic Phases. International Journal of Plasticity, 5, 551-572.

[4]   Taleb, L. and Sidoroff, F. (2003) A Micromechanical Modeling of the Greenwood-Johnson Mechanism in Transformation Induced Plasticity. International Journal of Plasticity, 19, 1821-1842.

[5]   Inoue, T. (2007) Unified Transformation-Thermoplasticity and the Application. Journal of the Society of Materials Science Japan, 56, 352-356.

[6]   Levitas, V.I. and Ozsoy, I.B. (2009) Micromechanical Modeling of Stress-Induced Phase Transformations. Part 1. Thermodynamics and Kinetics of Coupled Interface Propagation and Reorientation. International Journal of Plasticity, 25, 239-280.

[7]   Uehara, T. (2015) Molecular Dynamics Simulation on Transformation-Induced Plastic Deformation Using a Lennard-Jones Model. Key Engineering Materials, 626, 414-419.

[8]   Inoue, T., Ju, D.Y. and Arimoto, K. (1992) Metallo-Thermomechanical Simulation of Quenching Process—Theory and Implementation of Computer Code HEARTS. Proceedings of the 1st International Conference on Quenching and the Control of Distortion, Chicago, IL, 22-25 September 1992, 205-212.

[9]   Ju, D.Y., Mukai, R. and Sakamaki, T. (2011) Development and Application of Computer Simulation Code COSMAP on Induction Heat Treatment Process. International Heat Treatment and Surface Engineering, 5, 65-68.

[10]   Provatas, N. and Elder, K. (2010) Phase-Field Methods in Materials Science and Engineering. Wiley-VCH, Weinheim.

[11]   Schulz, S. (2016) Phase-Field Simulations of Multi-Component Solidification and Coarsening Based on Thermodynamic Datasets. KIT Scientific Publishing, Germany.

[12]   Sekido, K., Ohmura, T., Hara, T. and Tsuzaki, K. (2012) Effect of Dislocation Density on the Initiation of Plastic Deformation on Fe-C Steels. Materials Transactions, 53, 907-912.

[13]   Hata, K., Fujiwara, K., Kawano, K., Sugiyama, M., Fukuda, T. and Kakeshita, T. (2018) Three-Dimensional EBSD Analysis and TEM Observation for Interface Microstructure during Reverse Phase Transformation in Low Carbon Steels. ISIJ International, 58, 742-750.

[14]   Engin, C. and Urbassek, H.M. (2008) Molecular-Dynamics Investigation of the FCC→BCC Phase Transformation in Fe. Computational Materials Science, 41, 297- 304.

[15]   Tateyama, S., Shibuta, Y. and Suzuki, T. (2010) Orientation Relationship in FCC- BCC Phase Transformation Kinetics of Iron: A Molecular Dynamics Study. ISIJ International, 50, 1211-1216.

[16]   Li, G., Sui, X., Qin, X., Ma, Y., Wang, K. and Wang Q. (2016) Structural Transformation between BCC and FCC in Fe-Ni Nanoparticle during Heating Process. Physics Letters A, 380, 3500-3504.

[17]   Ou, X. (2017) Molecular Dynamics Simulations of FCC-to-BCC Transformation in Pure Iron: A Review. Materials Science and Technology, 33, 822-835.

[18]   Nguyen, T.Q., Sato, K. and Shibutani, Y. (2018) First-Principles Study of BCC/FCC Phase Transition Promoted by Interstitial Carbon in Iron. Materials Transactions, 59, 870-875.

[19]   Meiser, J. and Urbassek, H.M. (2018) Ferrite-to-Austenite and Austenite-to-Mar- tensite Phase Transformations in the Vicinity of a Cementite Particle: A Molecular Dynamics Approach. Metals, 8, 837.

[20]   Girifalco, L.A. and Weizer, V.G. (1959) Application of the Morse Potential Function to Cubic Metals. Physical Review, 114, 687-690.

[21]   Sandoval, L., Urbassek, H.M. and Entel, P. (2009) The Bain versus Nishiyama- Wassermann Path in the Martensitic Transformation of Fe. New Journal of Physics, 11, Article ID: 103027.

[22]   Uehara, T. (2017) Molecular Dynamics Simulation of Grain Refinement in a Polycrystalline Material under Severe Compressive Deformation. Materials Sciences and Applications, 8, 918-932.

[23]   Uehara, T. (2018) Molecular Dynamics Simulation of the Initiation of Plastic Deformation in Nanocrystalline Material. Proceedings of 9th International Conference on Computational Methods, Rome, 6-10 August 2018, 700-705.

[24]   Wei, W., Liu, L.C., Gong, H.R., Song, M., Chang, M.L. and Chen, D.C. (2019) Fundamental Mechanism of BCC-FCC Phase Transition from a Constructed PdCu Potential through Molecular Dynamics Simulation. Computational Materials Science, 159, 440-447.