ISSUE 2/2010

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Kozhar, S.; Regener, D.; Zak, H.; Altenbach, H.
A low cycle fatigue behaviour of a cast eutectic aluminium-silicon alloy AlSi12CuNiMg at elevated temperature

Eutectic AlSi12CuNiMg cast alloy combines excellent mechanical properties with good castability and is commonly used for piston applications. The aim of the present investigation is to find correlations between the microstructure and the low cycle fatigue behaviour of this alloy at 300 °C. The alloy was studied in both P-refined and Sr-modified conditions. In addition, T6 heat treatment was used to affect the microstructure and hardness of the AlSi12CuNiMg alloy. The combination of the structure modification and the heat treatment provided a broad range of samples with different morphology and size of silicon particles as well as hardness of the alloy for comparison purposes. It was found that under applied maximum stress higher than 65 MPa the low cycle fatigue of refined and modified AlSi12CuNiMg piston alloys can be significantly improved by T6 heat treatment due to the dominating effect of matrix hardening. Porosity, coarse silicon particles and intermetallic phases were determined as the most important crack propagation sites. Compared with P-refined alloy, Sr-modified alloy has nearly perfect spheroidization of eutectic silicon particles after heat treatment which improves the low cycle fatigue behaviour.

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