Comparison between 2D and 3D Characterisations of Damage Induced by Superplastic Deformation

H.Q. Yu et al., "Comparison between 2D and 3D Characterisations of Damage Induced by Superplastic Deformation ", Materials Science Forum, Vols. 447-448, pp. 55-60, 2004

Online since:

February 2004

Authors:

H.Q. Yu, Jean Jacques Blandin, L. Salvo

Keywords:

2D Data, 3D Data, Aluminium Alloy, Cavitation, X-Ray Micro-Tomography

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References

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[5] J. Pilling: Mater. Sc. Tech., 1 (1985) p.461.

[6] C.F. Martin, C. Josserond, L. Salvo, J.J. Blandin, P. Cloetens, E. Boller: Scripta Mater., 42 (2000) p.375.

DOI: https://doi.org/10.1016/s1359-6462(99)00355-3

[7] J.J. Blandin, L. Salvo, Proceedings of ESAFORM Conference, (Ed. A.M. Habraken, Belgique 2001), p.713.

[8] L. Dupuy, J.J. Blandin: Acta Mater., 50 (2002) p.3251.

[9] C.F. Martin, J.J. Blandin, L. Salvo: Mater. Sc. Eng., A297 (2001) p.212.

[10] P. Cloetens, M. Pateyron-Salome, J.Y. Buffière, G. Peix, J. Baruchel, F. Peyrin, M. Schlenker: J. Appl. Phys., 81 (1997) p.5878.

DOI: https://doi.org/10.1063/1.364374

[11] L. Salvo, P. Cloetens, E. Maire, S. Zabler, J.J. Blandin, J.Y. Buffière, W. Ludwig, E. Boller, D. Bellet, C. Josserond: Nuclear Inst. And Methods in Physics Research B, 200 (2003) p.273.

DOI: https://doi.org/10.1016/s0168-583x(02)01689-0

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Paper TitlePages

Cavitation Behaviors in a Tetragonal Zirconia Polycrystal Subjected to Superplastic Deformations Measured by SANS Method

Authors: Stefanus Harjo, Yoshinobu Motohashi, Jan Šaroun, Vasyl Ryukhtin, Pavel Strunz, Matthias Baron, Rudolf Loidl

An Investigation of Cavitation in the Tensile Testing of a Spray-Cast Aluminum Alloy Processed by ECAP

Authors: Megumi Kawasaki, Cheng Xu, Terence G. Langdon

Abstract: A commercial aluminum 7034 alloy, produced by spray casting and having an initial grain size of ~2.1 μm, was subjected to equal-channel angular pressing (ECAP) through six passes at 473 K. In the as-pressed condition, the microstructure was reasonably homogeneous and the grain size was reduced to an ultrafine grain size of ~0.3 μm. This alloy contains MgZn2 and Al3Zr precipitates which restrict grain growth. In tensile testing at 673 K after processing by ECAP, an elongation of >1000% was achieved at a strain rate of 1.0 × 10-2 s-1 corresponding to high strain rate superplasticity. Quantitative cavity measurements were conducted on the specimens after tensile testing for both the as-received condition and after ECAP. These measurements reveal a significant number of small cavities in the samples and especially in the sample that exhibited a very high elongation. This paper describes the morphology of cavity development in the spray-cast aluminum alloy in both the as-received and as-pressed condition.

Cavitation Behavior of Ultra-Fine Grained Ti-6Al-4V Alloy Produced by Equal-Channel Angular Pressing

Authors: Young Gun Ko, Yong Nam Kwon, Jung Hwan Lee, Dong Hyuk Shin, Chong Soo Lee

Abstract: Cavitation behavior during superplastic flow of ultra-fine grained (UFG) Ti-6Al-4V alloy was established with the variation of grain size and misorientation. After imposing an effective strainup to 8 via equal-channel angular pressing (ECAP) at 873 K, alpha-phase grains were markedly refined from 11 μm to ≈ 0.3 μm, and misorientation angle was increased. Uniaxial-tension tests were conducted for initial coarse grained (CG) and two UFG alloys (ε = 4 and 8) at temperature of 973 K and strain rate of 10-4 s-1. Quantitative measurements of cavitation evidenced that both the average size and the area fraction of cavities significantly decreased with decreasing grain size and/or increasing misorientation. It was also found that, when compared to CG alloy, cavitation as well as diffused necking was less prevalent in UFG alloys, which was presumably due to the higher value of strain-rate sensitivity. Based on the several theoretical models describing the cavity growth behavior, the cavity growth mechanism in UFG alloys was suggested.

621

High Temperature Deformation and Associated 3D Characterisation of Damage in Magnesium Alloys

Authors: Pierre Lhuissier, A. Villanueva Fernandez, L. Salvo, Jean Jacques Blandin

Abstract: A way to overcome the low deformability of magnesium alloys at room temperature is toincrease the temperature of forming operations. The stress exponent n, which is known to be a keyparameter in the control of plastic stability, generally decreases when temperature increases.Nevertheless, low n-values are not enough to ensure large capacity of deformation since fracturecan also result from strain induced cavitation. In the present investigation, both the mechanisms ofhigh temperature deformation and damage were studied in selected Mg alloys. Since damage datacan also give information on the deformation mechanisms, the strain induce cavitation behaviourwas mainly studied thanks to X-ray micro tomography which provides 3D information like thecavity shapes or the variation with strain of the number of cavities. Moreover, additionally toconventional post mortem analyses, it was attempted to perform the 3D damage characterisation inin situ conditions, namely directly during high temperature deformation tests.

1128

4D Damage Characterization during Superplastic Deformation of Magnesium Alloys

Authors: Pierre Lhuissier, Mario Scheel, Luc Salvo, Elodie Boller, Marco Di Michiel, Jean Jacques Blandin

Abstract: As for aluminium alloys, magnesium alloys are generally sensitive to strain induced cavitation when they are deformed in superplastic conditions. It has been widely shown that X-ray micro tomography is a particularly efficient tool for studying in 3D damage mechanisms during superplastic deformation. However, such characterisations are generally performed in post mortem conditions, namely on samples first deformed up to given strains and then characterised. In the present investigation, thanks to particularly short acquisition times offered by ESRF, damage induced by superplastic deformation of a magnesium alloy is studied thanks to tomography analyses performed in 4D conditions, namely directly during high temperature deformation tests. Such conditions provide unique opportunities for investigating nucleation, growth and coalescence of cavities since it is thus possible to follow each cavity up to the fracture process.