Creep Behavior of Dispersion-Hardened Aluminum Materials
Tóm tắt
Dispersion-hardened aluminum materials of pure aluminum with extremely fine oxide and carbide dispersions and very fine grain sizes were creep-deformed under compressive loadings between 573 and 773 K. The creep behavior of the investigated materials is influenced by time, temperature, stress level and microstructure. An increasing content of dispersions causes increasing threshold stresses σthand resistances against creep. The Norton plots of the minimum creep rate
$$\dot \varepsilon _{\min } $$
versus stress σ are characterized by extremely high stress exponents n. On the basis of the threshold concept it is demonstrated that the same diffusion process dominates in the dispersion-hardened aluminum materials as in pure aluminum. Their true stress exponents n*as the slopes of the best fit lines of the
$$\log \dot \varepsilon _{\min } {\text{ }}versus{\text{ }}\log (\sigma - \sigma _{{\text{th}}} )$$
are close to 5. The threshold stress decreases considerably with increasing temperature due to the thermally activated recovery of long-range internal back stresses of quasi-planar dislocation structures on the grain boundaries.
Tài liệu tham khảo
Arnhold, V. and Hummert, K., ‘Properties and application of dispersion strengthened aluminum alloys', in New Materials by Mechanical Alloying Technique, E. Arzt and L. Schultz (eds.), DGM-Informationsgesellschaft, Oberursel, 1989, 263–278.
Arzt, E. and Rösler, J., ‘The kinetics of dislocation climb over hard particles – II. Effects of an attractive particle-dislocation interaction', Acta Metall. 36, 1988, 1053–1060.
Blum, W., ‘High-temperature deformation and creep of crystalline solids', in Plastic Deformation and Fracture, H. Mughrabi (ed.), Materials Science and Technology, Vol. 6, VCH, Weinheim, 1993, 359–405.
Cadek, J., Oikawa, H. and Sustek, V., ‘Threshold creep behaviour of discontinuous aluminium and aluminium alloy matrix composites: An overview', Mater. Sci. Engrg. A190, 1995, 9–23.
Dobes, F., Kucharova, K., Orlova, A., Milicka, K. and Cadek, J., ‘Interpretation of steady-state creep rate in mechanically alloyed Al-C-O alloys', Acta Metall. Mater. 42, 1994, 1447–1455.
El-Magd, E., Ismail, Y., Brockmann, G.J. and Baumgarten, J, ‘Influence of the dispersoid material and forming process on the creep behaviour of dispersion strengthened aluminium', Mat. Wiss. u. Werkstofftech. 28, 1997, 34–39.
Jangg, G., Kuttner, F. and Korb, G., ‘Herstellung und Eigenschaften von dispersionsgehärtetem Aluminium', Aluminium 51, 1975, 641–645.
König, G. and Blum, W., ‘Comparison between the cell structures produced in aluminium by cycling and monotonic creep', Acta Metall. 28, 1980, 519–537.
Korb, G., Jangg, G. and Kuttner, F., ‘Neue technologische Entwicklungen bei der Dispersionshärtung von Aluminium und Kupfer', Draht 30, 1979, 318–323.
Kröpfl, I., ‘Verformungs-und Bruchverhalten von Oxid-sowie Karbid-und Oxiddispersionsverfestigten Aluminiumwerkstoffen', Dr.-Ing. Thesis, Universität Karlsruhe, 1996.
Kröpfl, I., Lang, K.-H., Vöhringer, O. and Macherauch, E., ‘Quasistatic deformation behaviour of dispersion-hardened aluminum materials', in Aluminum Alloys – Their Physical and Mechanical Properties, ICAA-6, T. Sato, S. Kumai, T. Kobayashi and M. Murakami (eds.), The Japan Institute of Light Metals, Tokajashi, Japan, 1998, Vol. 2, 911–916.
Nix, W. and Ilschner, B., ‘Mechanisms controlling creep of single phase metals and alloys', in International Conference on Metals and Alloys, ICSMA 5, P. Haasen, V. Gerold and G. Kostorz (eds.), Pergamon Press, Oxford, 1980, Vol. 3, 1503–1530.
Pandey, A.B., Mishra, R.S. and Mahajan, R.J., ‘Steady state creep behaviour of silicon carbide particulate reinforced aluminium composites', Acta Metall. Mater. 40, 1992, 2045–2052.
Rösler, J., Joos, R. and Arzt, E., ‘Microstructure and creep properties of dispersion-strengthened aluminum alloys', Metall. Trans. 23A, 1992, 1521–1539.
Sherby, O.D., González-Doncel, G. and Ruano, O.A., ‘Threshold stresses in particle-hardened materials', in Creep and Fracture of Engineering Materials and Structures, J.C. Earthman and F.A. Mohamed (eds.), The Minerals, Metals & Materials Society, Warrendale, PA, 1997, 9–18.
Weber, J.H. and Schelleng, R.D., ‘Mechanical alloying of dispersion strengthened aluminum: A retrospective review', in Dispersion Strengthened Aluminum Alloys, Y.-W. Kim and W.M. Griffith (eds.), The Minerals, Metals & Miners Society, Warrendale, PA, 1988, 467–482.
Wilshire, B., ‘Creep mechanisms in oxide-dispersion-strengthened alloys', in Creep and Fracture of Engineering Materials and Structures, J.C. Earthman and F.A. Mohamed (eds.), The Minerals, Metals & Materials Society, Warrendale, PA, 1997, 19–28.