Journal of Failure Analysis and Prevention

, Volume 9, Issue 2, pp 114–121 | Cite as

Effect of Microstructural Anisotropy on Mechanical Behavior of a High-Strength Al–Mg–Si Alloy

  • Muhammad Afzaal Malik
  • Iftikhar us Salam
  • Wali Muhammad
  • Noveed Ejaz
Case History---Peer-Reviewed


The mechanical behavior of an extruded aluminum alloy pipe has been investigated after repeated failures in an oil and gas industry. The pipe failures occurred by longitudinal cracking, and the mechanical properties of the pipe were blamed for the failure. The relevant critical properties of the pipe including basic tests of hardness, tensile, and impact behavior were measured, and extended fatigue testing of the material was conducted. Microstructural examination revealed a recrystallized grain structure and clusters of constituent particles aligned in the direction of extrusion. Tensile testing in both the longitudinal and circumferential directions showed virtually identical yield and tensile strengths. However, the material exhibited higher toughness in the longitudinal direction. Impact test showed that the energy absorbed during fracture was four times higher in the longitudinal direction. Fatigue testing displayed a shorter fatigue life in the transverse direction. The study showed that the microstructure after extrusion and the distribution of the constituent particles have a pronounced effect on the mechanical behavior of the extruded pipe and induced anisotropy in the material performance. Performance of the material can be improved by choosing the proper extrusion ratio to control the microstructure and by controlling the density and distribution of the constituent particles.


Aluminum alloy Extruded pipe Mechanical properties Anisotropy Fatigue crack growth 



The authors are highly indebted to the College of Electrical & Mechanical Engineering, National University of Sciences and Technology, Rawalpindi, Pakistan, for the support during this research work. Thanks are due to Mr. Wajid Rafique for his help in fatigue testing.


  1. 1.
    Salamci, E.: Directionality in the mechanical properties of spray cast and extruded 7XXX series aluminium alloys. Turkish J. Eng. Environ. Sci. 27, 169–176 (2003)Google Scholar
  2. 2.
    Varli, A.E., Gürbüz, R.: Fatigue crack growth behaviour of 6013 aluminium alloy at different ageing conditions in two orientations. Turkish J. Eng. Environ. Sci. 30, 381–386 (2006)Google Scholar
  3. 3.
    Heinz, A., Haszler, A., Keidel, C., Moldenhauer, S., Benedictus, R., Miller, W.S.: Recent development in aluminum alloys for aerospace applications. Mater. Sci. Eng. A 280, 102–107 (2000)CrossRefGoogle Scholar
  4. 4.
    Borrego, L.P., Ferreira, J.M., Pinho da Cruz, J.M., Costa, J.M.: Evaluation of overload effects on fatigue crack growth and closure. Eng. Fract. Mech. 70, 1379–1397 (2003)CrossRefGoogle Scholar
  5. 5.
    Oppenheim, T., Tewfic, S., Scheck, T., Klee, V., Lomeli, S., Dahir, W., Youngren, P., Aizpuru, N., Clark Jr, R., Lee, E.W., Ogren, J., Es-Said, O.S.: On the correlation of mechanical and physical properties of 6061-T6 and 7249-T76 aluminum alloys. Eng. Fail. Anal. 14, 218–225 (2007)CrossRefGoogle Scholar
  6. 6.
    Properties of wrought aluminum and aluminum alloys, Properties and Selection: Nonferrous Alloys and Special-Purpose Materials, vol. 2, 10th edn. Metals Handbook, ASM International, Materials Park, OH (1990)Google Scholar
  7. 7.
    “Standard Test Method for Measurement of Fatigue Crack Growth Rates”, E 647-05, Annual Book of ASTM Standards, ASTM, West Conshohocken, PA, pp. 692–719 (2005)Google Scholar
  8. 8.
    Srivatsan, T.S., Anand, S., Narendra, N.: Mechanisms governing deformation and damage during elevated-temperature fatigue of an aluminum-magnesium-silicon alloy. J. Mater. Eng. Perform. 6(2), 187–198 (1997)CrossRefGoogle Scholar
  9. 9.
    Yu, B.Y., Bao, C.L., Song, H.W., Liu, Z., Yu, H.P.: Microstructure and mechanical properties of AZ91D extruded tube. Acta Metall. Sin. (Engl. Lett.) 19(3), 203–208 (2006)CrossRefGoogle Scholar
  10. 10.
    Merati, A.: A study of nucleation and fatigue behavior of an aerospace aluminum alloy 2024-T3. Int. J. Fatigue 27, 33–44 (2005)CrossRefGoogle Scholar
  11. 11.
    Li, J.X., Zhai, T., Garratt, M.D., Bray, G.H.: Four-point-bend fatigue of AA 2026 aluminum alloys. Metall. Mater. Trans. A 36A, 2529–2539 (2005)CrossRefGoogle Scholar

Copyright information

© ASM International 2009

Authors and Affiliations

  • Muhammad Afzaal Malik
    • 1
  • Iftikhar us Salam
    • 1
  • Wali Muhammad
    • 1
  • Noveed Ejaz
    • 1
  1. 1.Department of Mechanical Engineering, College of Electrical and Mechanical EngineeringNational University of Sciences & TechnologyRawalpindiPakistan

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