Instantaneous creep in face-centered cubic metals at ultralow strain rates by a high-resolution strain measurement

Abstract

Instantaneous creep in face-centered cubic metals, 5N Al (99.999%), 2N Al (99%) and 4N Cu (99.99%) with different grain sizes, was firstly investigated by sudden stress-change experiments at ultralow strain rates $\dot \varepsilon $ ⩽ 10⁻¹⁰ s⁻¹ and temperature T < 0.32 T _m. The experimental results indicate that the observed instantaneous creep is strongly dependent on grain size, the concentration of impurity, and stacking fault energy. Creep in high-purity aluminum, 5N Al, with a very large grain size, d _g > 1600 μm, shows non-viscous behavior, and is controlled by the recovery of dislocations in the boundary of dislocation cells. On the other hand, for 5N Al with a small grain size, d _g=30 μm, and low-purity aluminum, 2N Al, with d _g= 25 μm, creep shows viscous behavior and may be related to ‘low temperature grain boundary sliding’. For high-purity copper, 4N Cu, with d _g= 40 μm and lower stacking fault energy, creep shows a non-viscous behavior, and is controlled by the recovery process of dislocations. For all of the samples, creep shows anelastic behavior.

Keywords

face-centered cubic metals / instantaneous creep / ultra-low strain rate / high strain resolution measurement

References

[1] Kimura K, Kushima H, Sawada K Long-term Creep Deformation Property of Modified 9 Cr -1 Mo Steel [J]. Mater. Sci. Eng. A, 2009, 510: 58-63.

[2] Kimura K, Toda Y, Kushima H, . Creep Strength of High Chromium Steel with Ferrite Matrix [J]. Int. J. Pres. Ves. and Pip., 2010, 87(6): 282-288.

[3] Haney EM, Dalle F, Sauzay M, . Macroscopic Results of Long-Term Creep on a Modified 9 Cr-1 Mo Steel (T91) [J]. Mater. Sci. Eng. A, 2009, 510: 99-103.

[4] Maruyama K, Karashima S Theoretical Consideration of Measurement of Work-Hardening and Recovery Rates during High Temperature Creep [J]. Trans. Japan Inst. Metals, 1975, 16(11): 671-678.

[5] Abe K, Yoshinaga H, Morozumi S A Method of Discerning Frictional Stress and Internal Stress by the Stress Relaxation Test [J]. Trans. Japan Inst. Metals, 1977, 18(6): 479-487.

[6] Oikawa H, Sugawara K Instantaneous Plastic Strain Associated with Stress Increments during the Steady State Creep of Al and Al - 5.5 At. Pct. Mg alloy [J]. Scripta Metall., 1978, 12(1): 85-89.

[7] Kloc L, Marĕk P Measurement of Very Low Creep Strains: A Review [J]. J. Test. Eval., 2009, 37: 53-58.

[8] Shen JJ, Yamasaki S, Ikeda K, Hata S, Nakashima H Low-temperature Creep at Ultra-low Strain Rates in Pure Aluminum Studied by a Helicoid Spring Specimen Technique [J]. Mater. Trans., 2011, 52(7): 1 381-1 387.

[9] Shen JJ, Ikeda K, Hata S, Nakashima H Transient Creep in Highpurity Aluminum at Ultra-low Stain Rate and Room Temperature by Constant Stress and Changing-stress Experiments[J]. Mater. Trans., 2011, 52(10): 1 885-1 889.

[10] Timoshenko S, Yong DH Elements of Strength of Materials[M], 1968 Fifth ed New York Van Nostrand 77-80.

[11] Wahi AM Mechanical Springs[M], 1963 Second ed New York McGraw-Hill 229-230.

[12] Ishibashi M, Fujimoto K, Ikeda K, . High Temperature Deformation Behavior of Sn-based Solder Alloys under Low Stress Conditions by a Helical Spring Creep Testing Method [J]. J. Japan Inst. Metals, 2009, 73(5): 373-380.

[13] Bradield G Use in Industry of Elasticity Measurements in Metals with the Help of Mechanical Vibrations [C], 1964

[14] Crossland IG, Jones RB, Levthewaite GW The Use of Helically Coiled Springs in Creep Experiments with Special Reference to the Case of Bingham flow [J]. J. Phys. D, 1973, 6(9): 1 040-1 046.

[15] Smallman RE, Bishop RJ Modern Physical Metallurgy and Materials Engineering [C]. Science, Process, Application, 2007 Seventh ed. Oxford Butterworth-Heinemann 100-101.