Effect of main alloying elements on strength of Al–Si foundry alloys at elevated temperatures

Abstract

In this study, we describe the effect of the main alloying elements Ni, Cu and Mg on the mechanical properties of near eutectic and hypoeutectic Al–Si foundry alloys at 250°C after a long term exposure to test temperature. Systematic compositional variations illustrate the significant hardening effect of secondary precipitates such as Al₂Cu and Mg₂Si. It is also shown that the strength is increased by the addition of Ni, albeit only to a certain level, depending on the fraction of eutectic phase in the alloy. The alloys are considered as coarse two-phase systems, where a hardening effect is caused by load transfer to the harder phase, which requires a certain contiguity of the latter. This paper discusses the individual influences of Ni, Cu and Mg on the high temperature strength and describes a potentially adverse effect of the combinations Cu/Ni and Cu/Mg.

Keywords:

• Al–Si foundry alloy
• Compositional variations
• High temperature strength
• Hardening effect

The authors would like to thank AMAG Austria Metall AG and the Austrian Research Promotion Agency for the financial support of this research project and for the permission to publish the results.