本研究利用霍普金森高速撞擊試驗機，測試4140合金鋼在不同溫度，及高應變速率荷載下的巨觀機械性質以及微觀結構變化。實驗溫度分別為25℃、200℃、400℃及700℃；應變速率為1000s-1、3000 s-1、5000 s-1，以了解溫度及應變速率對材料塑變行為及微觀結構之影響。結果顯示，巨觀機械性質會隨著溫度、應變速率以及應變量的變化而改變。固定溫度條件時，塑流應力值、加工硬化率及應變速率敏感性係數皆隨著應變速率的增加而增加，而熱活化體積則會下降。相反的，固定應變速率條件時，塑流應力值，加工硬化率、應變速率敏感性係數會隨溫度上升而下降，而熱活化體積則會上升。此外，藉由修正後的Zerilli-Armstrong構成方程式，準確預測此材料在其他溫度及應變速率下的應力值。在微觀結果方面，光學式顯微鏡之觀測可發現晶粒組織形貌的改變，及不同的溫度及應變速率對剪切帶的形貌與流線方向的影響。而穿透式電子顯微鏡則可觀察到大量差排的產生與糾結、疊差缺陷及滑移帶的出現。最後，藉由差排密度、差排胞尺寸、塑流應力值、應變速率敏感性係數及熱活化體積之連結，解析巨觀機械性質與微觀結構之相依性。

In this study, a split Hopkinson pressure bar tester is utilized to investigate the macro-mechanical properties and microstructural variation of AISI 4140 alloy steel under high strain-rate loadings over wide temperature range. The specimens are deformed at 25℃, 200℃, 400℃ and 700℃under the strain rates of 1000s-1, 3000s-1 and 5000s-1, respectively. The influence of temperature and strain rate on plastic deformation and microstructure is evaluated. The experimental results indicate that the mechanical properties are related to temperature, strain rate and strain. At a constant temperature, plastic stress, work hardening rate and strain rate sensitivity all increase with the increasing strain rate, while the thermal activation volume decreases. However, at a constant strain rate, plastic stress, work hardening rate and strain rate sensitivity decrease with increasing temperature, while the thermal activation volume increases. A modified Zerilli-Armstrong constitutive equation is used to predict flow behavior under different temperatures and strain rates. OM observation results indicate that the morphology of deformed grain and shear band as well as the plastic flow direction varied with strain rate and temperature. TEM microstructure observations reveal that the dislocation density increases with the increasing strain rate, but decreases with the increasing temperature. The higher dislocation density prompts a reduction in the dislocation cell size. Finally, the variations of the flow stress, strain rate sensitivity and thermal activation volume are correlated to dislocation cell size.

1. A. R. Causey, G. J. C. Carpenter and S. R. Macewen, “In-Reactor Stress Relaxation of Selected Metals and Alloys at Low Temperature”, Journal of Nuclear Materials, pp. 216-223, 1980.
2. S. H. Choo, S. Lee, M. G. Golkovski, “Effects of Accelerated Electron Beam Irradiation on Surface Hardening and Fatigue Properties in an AISI 4140 Steel Used for Automotive Crankshaft”, Materials Science and Engineering A, Vol. 293, pp. 56-70, 2000.
3. J. W. Zhang, L. T. Lu, K. Shiozawa, G. D. Cui, W. H. Zhang, “Fatigue Properties of Oxynitrocarburized Medium Carbon Railway Axle Steel in Very High Cycle Regime”, International Journal of Fatigue, Vol. 32, Colorado, pp. 1805-1811, 2010
4. M. Zlatanović, N. Popović, M. Mitrić, “Plasma Processing in Carbon Containing Atmosphere for Possible Treatment of Wind Turbine Components”, Thin Solid Films, Vol. 516, Belgrade, Yugoslavia, pp. 228-232, 2007.
5. J. Abella, I. Balachov, D. D. Macdonald, P. J. Millet, “Transport Process in Steam Generator Crevices III. Experimental Results”, Corrosion Science, Vol. 44, pp 191-205, 2002.
6. R. Menig, V. Schulze, O. Vo¨hringer, “Optimized Warm Peening of the Quenched and Tempered Steel AISI 4140”, Materials Science and Engineering A, Vol. 335, pp. 198-206, 2002.
7. B. Podgornik, J. Vižintin, O. Wänstrand, M. Larsson, S. Hogmarkb, H. Ronkainen, K. Holmberg, “Tribological Properties of Plasma Nitrided and Hard Coated AISI 4140 Steel”, Wear, Vol. 249, pp. 254-259, 2001.
8. A. H. Meysami, R. Ghasemzadeh, S. H. Seyedein, M. R. Aboutalebi, “An Investigation on the Microstructure and Mechanical Properties of Direct-quenched and Tempered AISI 4140 Steel”, Materials and Design, Vol. 31, pp. 1570-1575, 2010.
9. Y. C. Lin, M. S. Chen, J. Zhong, “Effect of Temperature and Strain Rate on the Compressive Deformation Behavior of 42CrMo Steel”, Journal of Materials Processing Technology, Vol. 205, pp. 308-315, 2008.
10. H. H. Lee and H. H. Uhlig, “Corrosion Fatigue of Type 4140 High Strength Steel”, Metallurgy Transaction, Vol. 3, pp. 2949-2957, 1975.
11. N. R. Dhar, S. Paul, A. B. Chattopadhyay, “Machining of AISI 4140 Steel Under Cryogenic Cooling-tool Wear, Surface Roughness and Dimensional Deviation”, Journal of Materials Processing Technology, Vol. 123, pp 483-489, 2002.
12. H. Kolsky “An Investigation of the Mechanical Properties of Materials at very High Rates of Loading” Proceeding of the Physical Society , Vol. 62, pp. 676-699, 1949.
13. F. E. Hauser, “Techniques for Measuring Stress-Strain Relations at High Strain Rate”, Experimental Mechanics, Vol. 6, pp 395-406, 1966.
14. A. J. Holzer, R. H. Brown, “Mechanical Behaviors of Metals in Dynamic Compression”, Journal of Engineering Materials and Technology, Vol. 101, pp. 238-247, 1979.
15. S. Nemat-Nasser and J. B. Isaacs, “Direct Measurement of Isothermal Flow Stress of Metals at Elevated Temperatures and High Strain Rates with Application to Ta and TaW Alloys”, Acta Materialia. Vol. 45, No. 3, pp. 907-919, 1997.
16. K. A. Hartleya, J. Duffya and R. H. Hawley, “Measurement of the Temperature Profile During Shear Band Formation in Steels Deforming at High Strain Rates”, Journal of the Mechanics and Physics of Solids, Vol. 35, No. 3, pp. 283-301, 1987.
17. S. C. Liao and J. Duffy, “Adiabatic Shear Bands in a Ti-6Al-4V Titanium Alloy”, Journal of the Mechanics and Physics of Solids, Vol. 46, No. 11, pp. 2201-2231, 1998
18. A. Marchand and J. Duffy, “An Experimental Study of the Formation Process of Adiabatic Shear Bands in a Structural Steel”, Journal of the Mechanics and Physics of Solids, Vol. 36, No. 3, pp. 251 283. 1988
19. Y. B. Xu, Y. L. Bai, Q. Xue and L. T. Shen, “Formation, Microstructure and Development of the Localized Shear Deformation in Low-carbon Steel”, Acta materialia. Vol. 44, No. 5, pp. 1917-1926, 1996
20. I. Kramerj, Unior Member A.I.M.E., R. H. Hafner and S. Toleman, “Effect of Sixteen Alloying Elements on Hardenability of Steel”, Metals Techonologys, Technical Publication, No. 1636, 1943.
21. D. R. Curran, L. Seaman and D. A. Shockey, “Linking Dynamic Fracture to Microstructural Process, Shock Wave and High-Strain-Rate Phenomena in Metal: Concepts and Applications”, pp. 22-26, 1980.
22. U. S. Lindholm, in Techniques in Metals Research, Vol. 5, Part1, R. F. Bunshah (ed.), Wiley-Interscience, New York, pp. 199, 1971.
23. U. S. Lindholm and L. W. Yeakly, “High Strain Rate Tension and Compression”, Experimental Mechanics, Vol. 3, pp. 81-88, 1983.
24. W. S. Lee and C. F. Lin, “Plastic Deformation and Fracture Behaviour of Ti-6Al-4V Alloy Loaded with High Strain Rate under Various Temperatures”, Materials Science and Engineering A, Vol. 241, pp. 48-59, 1998.
25. J. D. Campbell, “Dynamic Plasticity: Macroscopic and Microscopic Aspects”, Materials Science and Engineering A, Vol. 12, pp. 3-21, 1973.
26. D. Klahn, A. K. Mukherjee and J. E. Dorn, Proceedings of the 2nd International Conference on the Strength of Metals and Alloys, Vol. III, ASM, pp. 951, 1970.
27. J. D. Campbell and W. G. Ferguson, “The Temperature and Strain-Rate Dependence of the Shear Strength of Mild Steel”, Philosophical magazine, Vol. 21, pp. 63-82, 1970.
28. A. Seeger, “Dislocation and Mechanical Properties of Crystals”, Philosophical magazine, Vol. 46, pp. 1194-1217, 1955.
29. H. Conrad, “Thermally Activated Deformation of Metals”, Journal of Metal, pp. 582-588, 1964.
30. M. A. Meyers, D. J. Benson, O. Vo¨hringer, B. K. Kad, Q. Xue, H. H. Fu, “Constitutive Description of Dynamic Deformation: Physically-based Mechanisms”, Materials Science and Engineering, Vol. 322, pp. 194–216, 2002.
31. W. G. Ferguson, A. Kumar and J. E. Dorn, “Dislocation Damping in Aluminum at High Strain Rates”, Journal of Applied Physics, Vol. 38, pp. 1863-1869, 1967.
32. U. S. Lindholm and L. M. Yeakly, “Dynamic Deformation of Single and Polycrystalline Aluminum”, Journal of the Mechanics and Physics of Solids, Vol. 13, pp. 41-49, 1965.
33. J. D. Campbell and A. R. Dowling, “The Behaviour of Materials Subjected to Dynamic Incremental Shear Loading”, J. Mech. Phys. Solids, Vol. 18, pp. 43-63, 1970.
34. Y. Bai and B. Dodd, Adiabatic Shear Localization, Pergamon Press, pp. 104-124, 1992.
35. Z. Gronostajski, “The Constitutive Equations for FEM Analysis”, Journal of. Material. Processing Technology, Vol. 106, pp. 40-44, 2000.
36. L. W. Meyer, N. Herzig, T. Halle, F. Hahn, L. Krueger and K. P. Staudhammer, “A Basic Approach for Strain Rate Dependent Energy Conversion Including Heat Transfer Effects: An Experimental and Numerical Study”, Journal of. Material. Processing Technology, Vol. 182, pp. 319-326, 2007.
37. F. J. Zerilli and R. W. Armstrong, “Dislocation-Mechanics-Based Constitutive Relations for Material Dynamics Calculations”, Journal of Applied Physics, Vol. 61, pp. 1816-1825, 1987.
38. F. J. Zerilli and R. W. Armstrong, “Constitutive Equation for HCP Metals and High Strength Alloy Steels”, in High Strain Rate Effects on Polymer, Metal and Ceramic Matrix Composites and Other Advanced Materials, AD-Vol. 48, pp. 121-126, 1995.
39. D. Umbrello, R. M‘Saoubi and J. C. Outeiro, “The Influence of Johnson-Cook Material Constants on Finite Element Simulation of Machining of AISI 316L Steel”, International Journal of Machine Tools and Manufacture, Vol. 47, pp. 462-470, 2007.
40. U. R. Andrade, M. A. Meyers and A. H. Chokshi, “Constitutive Description of Work- and Shock-Hardened Copper”, Scripta Metallurgica et Materialia, Vol. 30, No. 7, pp. 933-938, 1994.
41. W. S. Lee, C. Y. Liu and B. K. Wang “The Correction of Wave Dispersion of the Split Hopkinson Pressure Bar During Discrete Fourier Transformation”, Journal of Iron Steel Institute., pp 12-13, 2003.
42. W. S. Lee and T. H. Chen, “Dynamic Deformation Behavior and Microstructural Evolution of High-Strength Weldable Aluminum Scandium (Al-Sc) Alloy”, Materials Transactions, Vol. 49, No. 6 pp. 1284-1293, 2008.
43. S. Esmaeili, L. M. Cheng, A. Deschamps, D. J. Lloyd, W. J. Poole, “The Deformation Behaviour of AA6111 as a Function of Temperature and Precipitation State”, Materials Science and Engineering A , Vol. 319-321, pp. 461-465, December 2001.
44. B. Viguier, “Dislocation Densities and Strain Hardening Rate in Some Intermetallic Compounds”, Materials Science and Engineering A, Vol. 349, pp. 132-135, 2003.
45. D. CHU and J. W. MORRIS, Jr, M. A. “The Influence of Microstructure on Work Hardening in Aluminum”, Acta Materialia, Vol. 44, No. 7, pp. 2599-2610, 1996.
46. J. Harding: “Effect of Temperature and Strain Rate on Strength and Ductility of Four Alloy Steels”, Metals Technology. Vol. 4, pp. 6-16. Jan. 1977.
47. L. SHI and D. O. NORTHWOOD, “The Mechanical Behavior of an AISI Type 310 Stainless Steel”, Acta Metallurgica et Materialia, Vol. 43, No. 2, pp. 453-460, 1995
48. S. R. Collins and G. M. Michal,”Effects of Processing on the Transverse Fatigue Properties of Low-Sulfur AISI 4140 Steel,” Metallurgical and Materials Transactions A, Vol.24, pp. 2701-2708, 1993.
49. B. Dood and Y. Bai, “Ductile Fracture and Ductility”, Academic Press Inc., London, p. 136, 1987.
50. R. S. Lakhkar, Y. C. Shin a, M. J. M. Krane, “Predictive Modeling of Multi-track Laser Hardening of AISI 4140 Steel”, Materials Science and Engineering A, Vol. 480, pp. 209–217, 2008.
51. R. W. K. Honeycombe, The Plastic Deformation of Metals, 2nd Edition, Edward Arnold, London, pp. 129-132, 1984.
52. M. A. Meyers and K. K, Chawla, Mechanical Metallurgy-Principles and Applications, Prentice-Hall, New Jersey, pp. 354-358, 1984.
53. I. Madariaga and I. Gutierrez “Role of the Particle±matrix Interface on the Nucleation of Acicular Ferrite in a Medium Carbon Microalloyed Steel”, Acta materialia, Vol. 47, No. 3, pp. 951-960, 1999.
54. I. Madariaga, I. Gutierrez, and H. K. D. H. Bhadeshia, “Acicular Ferrite Morphologies in a Medium-Carbon Microalloyed Steel”, Metallurgical and Materials Transactions A, Vol. 32, No. 9, pp. 2187-2197, 2001
55. T. Yamada, H. Terasaki and Y. I. Komizo, “Lattice Misfit between Inclusion and Acicular Ferrite in Weld Metal of Carbon Low Alloy Steel”, Journal of the Japan Welding Society, Vol. 27, No. 2, pp. 114-117, 2009.
56. C. Capdevila, J. P. Ferrer, C. Garcia-Mateo, F. G. Caballero, V. Lopez and C. G. D. Andres, “Influence of Deformation and Molybdenum Content on Acicular Ferrite Formation in Medium Carbon Steels”, ISIJ International, Vol. 46, No. 7, pp. 1093–1100, 2006.
57. W. Jin, C. Jun, Z. Zhen, R. Xue-yu, “Dynamic Recrystallization Behavior of Microalloyed Forged Steel”, Journal of Iron and Steel Research, International Vol. 15, Issue 3, pp. 78-81, 2008.
58. N. Fujita, R. Sahara, T. Narushima and C. Ouchi, “Austenitic Grain Growth behavior Immediately after Dynamic Recrystallization in HSLA Steels and Austenitic Stainless Steel”, ISIJ International, Vol. 48, No. 10, pp. 1419–1428, 2008.
59. M. E. Backman, S. A. Schulz, J. C. Schulz and J. K. Pringle, “Scaling Rules for Adiabatic Shear”, in Metallurgy Apllications of Shock Wave and High-strain Rate Phenomena (eds. L. E. Murr, K. P. Staudhammer and M. A. Meyers), pp. 675-688, Marcel Dekker Inc, New York, 1986.
60. A. G. Odeshia, M. N. Bassim, “High strain-rate fracture and failure of a high strength low alloy steel in compression”, Materials Science and Engineering: A Vol. 525, Issues 1-2, pp. 96-101, November 2009.
61. R. K. Ham, “The Determination of Dislocation Densities in Thin Films”, Philosophical Magazine, Vol. 6, pp. 1183-1184, 1961.
62. Y. Tomota, P. Lukas, S. Harjo, J-H. Park, N. Tsuchida, D. Neov, “In Situ Neutron Diffraction Study of IF and Ultra Low Carbon Steels upon Tensile Deformation”, Acta Materialia, Vol. 51, pp. 819-830, 2003.
63. M. Radovic, E. Lara-Curzio, L. Riester, “Comparison of Different Experimental Techniques for Setermination of Elastic Properties of Solids”, Materials Science and Engineering A, Vol. 368, Issues 1-2., pp. 56-70, 2004.
64. P. Trivedi, D. P. Field, H. Weiland, “Alloying Effects on Dislocation Substructure Evolution of Aluminum Alloys”, International Journal of Plasticity, Vol. 20, pp. 459-476, 2004.
65. M. A. Meryers, Dynamic Behavior of Materials, John Wiley & Sons, pp. 420-426, 1994.
66. M. A Meryers, Mechanical Metallurgy Principles and Applications, Prentice-Hall, pp. 284-289, 1984
67. F. Hamdi and S. Asgari, “Evaluation of the Role of Deformation Twinning in Work Hardening Behavior of Face-Centered-Cubic Polycrystals”, Metallurgical and Materials Transactions A, Vol. 39, No. 2, pp. 294-303, 2008.
68. C. O. Mgbokwere, S. R. Nutt and J. Duffy, “Shear Band Formation in 4340 steel: A TEM Study”, Mechanics of Materials, Vol. 17, Issues 2-3, pp. 97-110, 1994.
69. Q. Li, Y. B. Xu, Z. H. Lai, L. T. Shen, Y. L. Bai, “Dynamic Recrystallization Induced by Plastic Deformation at High Strain Rate in a Monel Alloy”, Materials Science and Engineering A, Vol. 276, Issues 1-2,pp. 250-256, 2000.