J. Mater. Sci. Technol. ›› 2016, Vol. 32 ›› Issue (6): 515-523.DOI: 10.1016/j.jmst.2016.03.010

Special Issue: 铝合金专辑

• Orginal Article • Previous Articles     Next Articles

Influence of Process Parameters and Sr Addition on the Microstructure and Casting Defects of LPDC A356 Alloy for Engine Blocks

Giulio Timelli*, Daniele Caliari, Jovid Rakhmonov   

  1. Department of Management and Engineering, University of Padova, Stradella S. Nicola, 3 I-36100 Vicenza, Italy
  • Received:2015-09-25 Online:2016-06-10
  • Contact: Corresponding author. Ph.D.; Tel.: +39 444 998769; Fax: +39 444 998889. (G. Timelli).E-mail address: timelli@gest.unipd.it (G. Timelli).
  • Supported by:
    The authors acknowledge Dr. R. Molina and Dr. M. Badiali from Teksid Aluminum Spa (Carmagnola, Italy) for the support to this research, and thank Dr. A. Guglielmi for the experimental contribution to this work.

Abstract: The effects of Sr addition and pressure increase on the microstructure and casting defects of a low-pressure die cast (LPDC) AlSi7Mg0.3 alloy have been studied. Metallographic and image analysis techniques have been used to quantitatively examine the microstructural changes and the amount of porosity occurring at different Sr levels and pressure parameters. The results indicate that an increase in the filling pressure induces lower heat dissipation of the liquid close to the die/core surfaces, with the formation of slightly greater dendrite arms and coarser eutectic Si particles. On the other hand, the increase in the Sr level leads to finer microstructural scale and eutectic Si. The analysed variables, within the experimental conditions, do not affect the morphology of eutectic Si particles. Higher applied pressure and Sr content generate castings with lower amount of porosity. However, as the filling pressure increases the flow of metal inside the die cavity is more turbulent, leading to the formation of oxide films and cold shots. In the analysed range of experimental conditions, the design of experiment methodology and the analysis of variance have been used to develop statistical models that accurately predict the average size of secondary dendrite arm spacing and the amount of porosity in the low-pressure die cast AlSi7Mg0.3 alloy.

Key words: Aluminium alloys, Engine block, Microstructure, Casting defects, Sr addition, Process parameters