Creep-rupture behavior of die-cast magnesium alloys
Keywords:
Die-Cast Mg alloys, Creep rupture, Monkman-grant relation, Apparent activation energyAbstract
It is found that the relationship between the time-to-rupture tr and the time to the onset of tertiary creep tοt (tr/tot) in die-cast Mg-9Al alloy is equal to 1.3 and independent of stress, test temperature and diecasting parameters over the range examined. It is shown that the introduction of creep-rupture strain into Monkman-Grant relation modified by DobeÅ¡ and MiliÄka demonstrates only the deviation range of the minimum creep rate from the average creep rate. The apparent activation energy Ec of creep is below the value of magnesium self-diffusion energy ESD up to 175°C. At higher temperatures, Ec > ESD, and creep deformation may be controlled by diffusion processes (dislocation climbing, etc.). The established magnitude of stress exponent n in the power law (the modified Arrhenius rate equation) within the stress range from 20 to 50 MPa is close to the value of n ≅ 3 typical of solid-solution alloys. The increase in n values at higher stresses up to ~ 5 is caused, probably, by stress-induced precipitation of β-phase during long-term creep tests.Downloads
References
Askeland, D.R. 1994. The science and engineering of Materials. 3rd ed. Boston : PWS Publishing : 819.
Bernasconi, G. and Piatti, G. 1979. Creep of Engineering Materials and Structures. London : Applied Science Publishers.
Blum, W., Watzinger, B. and Weidinger, P. 1998. Creep resistance of Mg-base alloys. In: Mordike, B.L. and Kainer, K.U. (eds.), Magnesium Alloys and their Applications, MATINFO Werkstoff-Informationgeselschaft. Frankfurt, Germany : 49-60.
Chen, F.C., Jones, J. W., Mc Ginn, T.A., Kearns, J.E., Nielsen, A.J. and Allison, J.E. 1997. Bolt-load-retention and creep of die-cast Mg-alloys, In : Proc. Int. Congress & Exposition, Detroit, Michigan, February 24-27, 1997, SAE technical paper series, Paper Number 970325. Warrendale: The Society of Automotive Engineers. Pa : 13-21.
Dargush, M., Hisa, M., Caceres, C.H., and Dunlop, G.L. 1996. Elevated temperature deformation of die cast Mg alloy AZ91D. In : Proceed. Third Int. Magnesium Conf. The Institute of Materials, Manchester, England : 153-165.
Gittus, J. 1975. Creep, viscoelasticity and creep fracture in solids. London : Applied Science Publishers : 725.
Gold, M., Leyda, W.E. and Zeisloft, R.H. 1975. The effect of varying degree of cold work on the stress-rupture properties of type 304 stainless steel. Trans. ASME J. Eng. Mat. Technol. 97(4) Series H : 305–312.
Gutman, E.M., Unigovski, Ya.B., Levkovich, M., Aghion, E. and Dangur, M. 1997. Influence of technological parameters of permanent mold casting and die casting on creep and strength of magnesium alloy AZ91D. Mat. Sci. Eng. A, A234-236 : 880-883.
Gutman, E.M., Unigovski, Ya.B., Levkovich M. and Koren, Z. 1998. Porosity and casting condition influence on creep of die cast Mg-alloy. J. Mater. Sci. Lett. 17 : 1787- 1789.
Jones, W. 1992. Theory of creep deformation. In : ASM Metals Handbook. 10th ed. Vol. 8, Mechanical Testing. New York : ASM International, the Material Information Society : 308-310.
Miller, W.K. 1991. Creep of die-cast AZ91D magnesium at room temperature and low stress. Metall. Trans. A. 22(A) : 873-877.
Mitra, S.K. and McLean, D. 1966. Work Hardening and Recovery in Creep. Proc. R. Soc. 295 : 288–299.
Mohamed, F.A. and Langdon, T.G. 1994. The transition from dislocation climb to viscous glide in creep of solid solution alloys. Acta Metall. 22 : 779-788.
Monkman, F.C. and Grant, N.J. 1956. An empirical relationship between rupture life and minimum creep rate in creep-rupture tests. Am. Soc. Test. Mater. Proc. 56 : 593-620.
Raynor, G.V. 1959. The physical metallurgy of Magnesium and its Alloys. London : Pergamon Press : 521.
Regev, M., Aghion, E. and Rosen, A. 1997. Creep studies of AZ91D pressure die-casting. Mater. Sci. Eng. A. A234-236 : 123-126.
Sherby, O.D. 1962. Factors affecting the high temperature strength of polcyrystalline solids. Acta Metal. 10 : 135–147.
Sherby, O.D. and Burke, P.M. 1969. Mechanical behavior of crystalline solids at elevated temperature. Prog. Mat. Sci. 13 : 325-390.
Unigovski, Ya., Keren, Z. Eliezer, A. and Gutman, E.M. 2005. Creep behavior of pure magnesium and Mg–Al alloys in active environments. Mater. Sci. Eng. A398(1-2) : 188-197.
Vagarali, S.S. and Langdon, T.G. 1981. Deformation mechanism in H.C.P. metals at elevated temperatures-I. Creep behavior of magnesium. Acta Metall. 29 : 1969-1982.
Vagarali, S.S. and Langdon, T.G. 1982. Deformation mechanism in H.C.P. metals at elevated temperatures-II.Creep behavior of a Mg- 0.8% Al solid solution alloy. Acta Metall. 30 : 1157-1170.
Voorhees, H.R. 1992. Assessment and Use of Creep-Rupture Properties. In : ASM Metals Handbook. 10th ed. Vol. 8, Mechanical Testing. New York : ASM International, the Material Information Society : 838-885.
Downloads
Published
How to Cite
Issue
Section
License
Copyright (c) 2017 Journal of Metals, Materials and Minerals
This work is licensed under a Creative Commons Attribution-NonCommercial-NoDerivatives 4.0 International License.
Authors who publish in this journal agree to the following terms:
- Authors retain copyright and grant the journal right of first publication with the work simultaneously licensed under a Creative Commons Attribution License that allows others to share the work with an acknowledgment of the work's authorship and initial publication in this journal.
- Authors are able to enter into separate, additional contractual arrangements for the non-exclusive distribution of the journal's published version of the work (e.g., post it to an institutional repository or publish it in a book), with an acknowledgment of its initial publication in this journal.
