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Quality Index of Tensile Property on Porosity Variation in A356 Casting Alloys upon T6 Treatment

  • ChoongDo LeeEmail author
Article
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Abstract

The contribution of porosity variation affecting the tensile properties of A356 aluminium alloys was investigated in terms of the variations in the quality index of tensile properties as well as the strength coefficient and strain-hardening exponent associated with the T6-treatment. The test specimens were prepared using a low-pressure die-casting and subsequent T6-treatment, and the contribution of microporosity, microstructural features and strain-relating factors to quality index was quantitatively evaluated using a modified constitutive model. The quality index of A356 alloys increases gradually with the lapse of ageing time upon T6-treatment, which increases significantly at the initial ageing stage with rise in the ageing temperature. Additionally, the quality index of A356 alloy primarily depends on the porosity variation with power law relationship, irrespective of its state, i.e. solutionised or artificially aged. Theoretically, the strength coefficient directly determines the nominal level of quality index. The overall dependence of quality index on porosity variation is weakened with increasing tensile strain, but it significantly depends upon the porosity variation for lower values of the strain-hardening exponent. The age hardening arises an explicit transition on fracture path by the damage evolution of eutectic Si particles, which can influence the overall level of quality index through a change in the effective void area fraction, with the microporosity variation by pre-existing micro-voids in casting alloys.

Graphic abstract

A wide deviation on quality index of A356 casting alloy depends practically upon the microporosity variation. Additionally, the nominal level of quality index is influenced by the damage evolution of eutectic Si particles as well as the variation of strength coefficient and strain-hardening exponent by age hardening on T6-treatment. The theoretical approach by constitutive model can quantitatively describe the individual contributions of the strength coefficient and strain-hardening exponent to the overall level of quality index, including the microstructural features such as the area fraction and distribution aspect of micro-voids and eutectic Si particles.

Keywords

Tensile property A356 aluminium alloy Porosity Quality index 

Notes

Acknowledgements

This research was supported by the General Researcher Program through the National Research Foundation of Korea (NRF) and funded by the Ministry of Education, Science and Technology (NRF-2017R1D1A1B03028953).

References

  1. 1.
    M. Drouzy, S. Jacob, M. Richard, Interpretation of tensile results by means of quality index and probable yield strength. AFS Int. Cast Met. J. 5, 43–50 (1980)Google Scholar
  2. 2.
    C.H. Cáceres, Material properties and quality index in Al–Si–Mg casting alloys. AFS Trans. 106, 601–604 (1998)Google Scholar
  3. 3.
    C.H. Cáceres, A rationale for the quality index of Al–Si–Mg casting alloys. Int. J. Cast Met. Res. 12, 385–391 (2000)CrossRefGoogle Scholar
  4. 4.
    C.H. Cáceres, J.H. Sokolowski, P. Gallo, Effect of aging and Mg content on the quality index of two model Al-Cu-Si-Mg alloys. Mater. Sci. Eng., A 271, 53–61 (1999)CrossRefGoogle Scholar
  5. 5.
    C.H. Cáceres, J. Barresi, Selection of temper and Mg content to optimize the quality index of Al–7Si–Mg casting alloy. Int. J. Cast Met. Res. 12, 377–384 (2000)CrossRefGoogle Scholar
  6. 6.
    C.H. Cáceres, Microstructure design and heat treatment selection for casting alloys using the quality index. J. Mater. Eng. Perform. 9, 215–221 (2000)CrossRefGoogle Scholar
  7. 7.
    C.H. Cáceres, A phenomenological approach to the quality index of Al–Si–Mg casting alloy. Int. J. Cast Met. Res. 12, 367–375 (2000)CrossRefGoogle Scholar
  8. 8.
    G. Sigworth, Understanding quality in aluminum castings. Inter. Metalcast. 5, 7–22 (2011)CrossRefGoogle Scholar
  9. 9.
    M.F. Lbrahim, A.M. Samuel, H.W. Doty, F.M. Samuel, Effect of aging conditions on precipitation hardening in Al–Si–Mg and Al–Si–Cu–Mg alloys. Inter. Metalcast 11, 274–286 (2017)CrossRefGoogle Scholar
  10. 10.
    L. Alyaldin, M.H. Abdelaziz, A.M. Samuel, H.W. Doty, S. Valtierra, F.M. Samuel, Effects of alloying elements and testing temperature on the Q-index of Al–Si based alloys. Inter. Metalcast 12, 839–852 (2018)CrossRefGoogle Scholar
  11. 11.
    M. Tiryakioglu, J. Campbell, Quality index for aluminum alloy castings. Inter. Metalcast 8, 39–42 (2014)CrossRefGoogle Scholar
  12. 12.
    M. Riestra, A. Bjurenstedt, T. Bogdanoff, E. Ghassemali, S. Seifeddine, Complexities in the assessment of melt quality. Inter. Metalcast 12, 441–448 (2018)CrossRefGoogle Scholar
  13. 13.
    T.I. So, W.C. Jung, C.D. Lee, K.S. Shin, Effects of T6-treatment on the defect susceptibility of tensile strength to microporosity variation in low pressure die-cast A356 alloy. Met. Mater. Inter. 21, 842–849 (2015)CrossRefGoogle Scholar
  14. 14.
    C.D. Lee, Effect of artificial ageing on the defect susceptibility of tensile properties to porosity variation in A356 aluminium alloys. Inter. Metalcast 12, 321–330 (2018)CrossRefGoogle Scholar
  15. 15.
    A.K. Ghosh, Tensile instability and necking in materials with strain hardening and strain-rate hardening. Acta Metall. 25, 1413–1424 (1977)CrossRefGoogle Scholar
  16. 16.
    M.K. Surappa, E. Blank, J.C. Jaquet, Effect of macroporosity on the strength and ductility of cast Al–7Si–0.3Mg alloy. Scr. Metall. 20, 1281–1286 (1986)CrossRefGoogle Scholar
  17. 17.
    C.H. Cáceres, B.I. Selling, Casting defects and the tensile properties of an Al–Si–Mg alloy. Mater. Sci. Eng. A 220, 109–116 (1996)CrossRefGoogle Scholar
  18. 18.
    C.D. Lee, K.S. Shin, Constitutive prediction of the defect susceptibility of tensile properties to microporosity variation in A356 aluminum alloy. Mater. Sci. Eng. A 599, 223–232 (2014)CrossRefGoogle Scholar
  19. 19.
    C.D. Lee, K.S. Shin, Y.J. Kim, Dependence of tensile ductility on damage evolution of eutectic Si-particles and pre-existing micro-voids in Al–Si casting alloy. Eng. Mater. Fract. 175, 339–356 (2017)CrossRefGoogle Scholar
  20. 20.
    A.M. Gokhale, G.R. Patel, Quantitative fractographic analysis of variability in tensile ductility of a squeeze cast Al–Si–Mg base alloy. Mater. Charact. 54, 13–20 (2005)CrossRefGoogle Scholar
  21. 21.
    A.M. Gokhale, G.R. Patel, Origins of variability in the fracture-related mechanical properties of a tilt-pour-permanent-mold cast Al-alloy. Scr. Mater. 52, 237–241 (2005)CrossRefGoogle Scholar
  22. 22.
    C.D. Lee, Effect of damage evolution of Si particles on the variability of the tensile ductility of squeeze-cast Al–10%Si–2%Cu–0.4%Mg alloy. Mater. Sci. Eng. A 527, 3144–3150 (2010)CrossRefGoogle Scholar
  23. 23.
    M.D. Dighe, A.M. Gokhale, M.F. Horstemeyer, Effect of loading condition and stress state on damage evolution of silicon particles in an Al–Si–Mg-base cast alloy. Met. Mater. Trans. 33A, 555–565 (2002)CrossRefGoogle Scholar
  24. 24.
    J.R. Rice, D.M. Tracey, On the ductile enlargement of voids in triaxial stress fields. J. Mech. Phys. Solids 17, 201–217 (1969)CrossRefGoogle Scholar
  25. 25.
    A. Weck, D.S. Wilkinson, Experimental investigation of void coalescence in metallic sheets containing laser drilled holds. Acta Mater. 56, 1774–1784 (2008)CrossRefGoogle Scholar
  26. 26.
    P.F. Thomason, Ductile Fracture of Metals (Pergamon, Oxford, 1990)Google Scholar
  27. 27.
    C.H. Cáceres, T. Din, A.K.M.B. Rashid, J. Campbell, Effect of ageing on the quality index of an Al–Cu alloy. Mater. Sci. Technol 15, 711–716 (1999)CrossRefGoogle Scholar

Copyright information

© The Korean Institute of Metals and Materials 2019

Authors and Affiliations

  1. 1.Department of Metallurgical and Materials EngineeringInha Technical CollegeIncheonRepublic of Korea

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