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Microstructural features associated with the effect of temperature on the dimensional stability of an automotive Al-A319 alloy

  • Received: 07 March 2016 Accepted: 24 May 2016 Published: 26 May 2016
  • In this work an automotive Al-A319 was given a solid solution heat treatment (T4) at 753 K (480 °C) for 4.5 hours and an ageing treatment (T7) at 513 K (240 °C) for various times up to 3.0 h. The alloy in the T4 condition was dilatometrically tested at various temperatures in order to measure its relative dimensional changes. It was found that the dimensional changes are due to both, alloy thermal expansion and nucleation and growth of second phases. In addition, in the T7 condition the alloy strength and ductility were determined as a function of ageing times. Ageing promoted alloy strength but at the expenses of a rather poor alloy ductility (down to 1%). Apparently, Cu rich intermetallic phases and regions provided a brittle path for fracturing. In particular, microstructural characterization using high resolution transmission electron microscopy indicated that not all the Cu in the matrix was dissolved during the T4 treatment. Hence, after ageing (T7) these Cu-rich regions seemed to coarsen into spherical particles.

    Citation: Hugo F. Lopez. Microstructural features associated with the effect of temperature on the dimensional stability of an automotive Al-A319 alloy[J]. AIMS Materials Science, 2016, 3(2): 634-644. doi: 10.3934/matersci.2016.2.634

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  • In this work an automotive Al-A319 was given a solid solution heat treatment (T4) at 753 K (480 °C) for 4.5 hours and an ageing treatment (T7) at 513 K (240 °C) for various times up to 3.0 h. The alloy in the T4 condition was dilatometrically tested at various temperatures in order to measure its relative dimensional changes. It was found that the dimensional changes are due to both, alloy thermal expansion and nucleation and growth of second phases. In addition, in the T7 condition the alloy strength and ductility were determined as a function of ageing times. Ageing promoted alloy strength but at the expenses of a rather poor alloy ductility (down to 1%). Apparently, Cu rich intermetallic phases and regions provided a brittle path for fracturing. In particular, microstructural characterization using high resolution transmission electron microscopy indicated that not all the Cu in the matrix was dissolved during the T4 treatment. Hence, after ageing (T7) these Cu-rich regions seemed to coarsen into spherical particles.


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    [1] Rincon E, Lopez HF, Cisneros MM, et al. (2007) Effect of temperature on the tensile properties of an as-cast aluminum alloy A319. J Mats Sci Eng A 452 - 453: 682–687.
    [2] Rincon E, Lopez HF, Cisneros MM, et al. (2009) Temperature effects on the tensile properties of cast and heat treated aluminum alloy A319. J Mats Sci Eng A 519: 128–140.
    [3] Caceres CH, Svensson IL, Taylor JA (2002) Microstructural factors and the mechanical performance of al-Si-Mg and Al-Si Cu-Mg Casting alloys, Proceeds. 2nd Intl. Aluminum Casting Technology Symposium, Columbus Ohio. Eds. Tiryakioglu M and Campbell J. ASM Int., 49–57.
    [4] Tiryakioglu M, Campbell J, “Evaluating the structural quality of Cast Al-75 Si-Mg alloys by tensile deformation characteristics. Proceeds. 2nd Intl. Aluminum Casting Technology Symposium, Columbus Ohio, Eds. Tiryakioglu M and Campbell, ASM Int., 59–64.
    [5] Caceres CH, Svensson IL, Taylor JA (2003) Strength and ductility Behavior of Al-Si-Cu Mg casting alloys in T6 temper. Int J Cast Metals Res 15: 531–543.
    [6] Puncreobutr C, Lee PD, Kareh KM, et al. (2014) Influence of Fe-rich intermetallics on solidification defects in Al–Si–Cu alloys. Acta Mater 68: 42–51.
    [7] Aluminum Casting Technology (1997) in Metallography, Eds. American Foundry Society, 303–323
    [8] Aluminum, properties and physical metallurgy (1984) in precipitation heat treatment, Eds. ASM, 177–182.
    [9] Aluminum Casting Technology (1997) in Heat treatment and strengthening of aluminum castings, Eds. American Foundry Society, 287–302.
    [10] Brooks CR, Heat Treatment Structure and Properties of Nonferrous Alloys (1982) ASM, 95–114.
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