Abstract

A phase mixture model was employed to simulate the deformation behaviour of metallic materials covering a wide grain size range from micrometer to nanometer scale. In this model a polycrystalline material is treated as a mixture of two phases: grain interior phase whose plastic deformation is governed by dislocation and diffusion mechanisms and grain boundary 'phase' whose plastic flow is controlled by a boundary diffusion mechanism. The main target of this study was the effect of grain size on stress and its strain rate sensitivity as well as on the strain hardening. Conventional Hall-Petch behaviour in coarse grained materials at high strain rates governed by the dislocation glide mechanism was shown to be replaced with inverse Hall-Petch behaviour in ultrafine grained materials at low strain rates, when both phases deform predominantly by diffusion controlled mechanisms. The model predictions are illustrated by examples from literature.

주제어

#Nanocrystalline Materials   #Plastic Deformation   #Modelling   #Grain Boundary Diffusion   #Strain Rate Sensitivity   #Deformation Mechanisms   #Ductility  

저자의 다른 논문

참고문헌 (20)

1. R. Z. Valiev, 2002, Materials Science: Nanomaterial Advantage, Nature, vol.419, pp.887-888 
2. R. Z. Valiev, I. V. Alexandrov, Y. T. Zhu, T. C. Lowe, 2002, Paradox of Strength and Ductility in Metals Processed by Severe Plastic Deformation, J. Mater. Res., vol.17, pp.5-8 
3. L. Lu, M. L. Sui, K. Lu, 2000, Superplastic Extensibility of Nanocrystalline Copper at Room Temperature, Science, vol.287, pp.1463-1466 
4. W. Y. Wang, M. Chen, F. Zhou, E. Ma, 2002, High Tensile Ductility in a Nanostructured Metal, Nature, vol.419, pp.912-914 
5. Y. M. Wang, E. Ma, 2004, Three Strategies to Achieve Unif orm Tensile Deformation in a Nanostructured Metal, Acta Mater., vol.52, pp. 1699-1709 
6. H. S. Kim, Y. Estrin, M. B. Bush, 2000, Plastic Deformation Behaviour of Fine-Grained Materials, Acta Mater., vol.48, pp.493-504 
7. D. G. Morris, 1998, Mechanical Behaviour of Nanostructured Materials, Materials Science Foundations, vol.2 Trans Tech Publications Ltd, Switzerland 
8. V. Yamakov, D. Wolf, S. R. Phillpot, A. K. Mukherjee, H. Gleiter, 2002, Dislocation Processes in the Deformation of Nanocrystalline Aluminium by Molecular-Dynamics Simulation, Nature Mater., vol.1, pp. 45-49 
9. V. Yamakov, D. Wolf, S. R. Phillpot, H. Gleiter, 2002, Grain-Boundary Diffusion Creep in Nano-crystalline Palladium by Molecular-Dynamics Simulation, Acta Mater., vol.50, pp. 61-73 
10. H. S. Kim, 1998, A Composite Model for Mechanical Properties of Nanocrystalline Materials, Scripta Mater., vol.39, pp. I 057-1061 
11. H. S. Kim, M. B. Bush, 1999, The Effects of Grain Size and Porosity on The Elastic Modulus of Nanocrystalline Materials, Nanostruct. Mater., vol.11, pp. 361-367 
12. H. S. Kim, M. B. Bush, Y. Estrin, 2000, A Phase Mixture Model of a Particle Reinforced Composite with Fine Microstructure, Mater. Sci. Eng., vol. A276, pp. 175-185 
13. N. Wang, Z. Wang, K. T. Aust, U. Erb, 1995, Effect of Grain Size on Mechanical Properties of Nanocrystalline Materials, Acta Metall. Mater., vol. 43, pp. 519-528 
14. Y. Estrin, 1996, Unified Constitutive Laws of Plastic Deformation (Krausz, A. S. and Krausz, K. Eds.), Academic Press, New York, p. 69 
15. H. S. Kim, S. I. Hong, S. J. Kim, 2001, On the Rule of Mixtures for Predicting the Mechanical Properties of Composites with Homogeneously Distributed Soft and Hard Particles, J. Mater. Proc. Techn., vol. 112, pp. 109-113 
16. A. H. Chokshi, A. Rosen, J. Karch, H. Gleiter, 1989, On the Validity of the Hall-Petch Relationship in Nanocrystalline Materials, Scripta Metall., vol. 23, pp. 1679-1683 
17. R. Schwaiger, B. Moser, M. Dao, N. Chollacoop, S. Suresh, 2003, Some Critical Experiments on the Strain-Rate Sensitivity of Nanocrystalline Nickel, Acta Mater., vol. 51, pp. 5159-5172 
18. H. S. Kim, Y. Estrin, 2001, Ductility of Ultrafine Grained Copper, Appl, Phys. Lett., vol.79, pp. 4155-4117 
19. F. Dalla Torre, H. Van Swygenhoven, M. Victoria, 2002, Nanocrystalline Electrodeposited Ni: Microstructure and Tensile Properties, Acta Mater., vol. 50, pp. 3957-3970 
20. Y. Zhu, X. Liao, 2004, Nanostructured Metals: Retaining Ductility, Nature Mater., vol.3, pp.351-352 

이 논문을 인용한 문헌 (0)

1. 이 논문을 인용한 문헌 없음