The Effect of Ni on the High-Temperature Strength of Al-Si Cast Alloys

Florian Stadler; Helmut Antrekowitsch; Werner Fragner; Helmut Kaufmann; Peter J. Uggowitzer

doi:10.4028/www.scientific.net/MSF.690.274

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HomeMaterials Science ForumMaterials Science Forum Vol. 690The Effect of Ni on the High-Temperature Strength...

The Effect of Ni on the High-Temperature Strength of Al-Si Cast Alloys

Abstract:

In order to investigate the effect of Ni on the high-temperature strength of Al-Si cast alloys, tensile properties of hypoeutectic and eutectic alloys were determined at 250 °C after long-term annealing at test temperature. LOM- and SEM-analysis revealed the existence of Al₃Ni-phases in close contact to eutectic Si. It was shown that the strength can be increased by the addition of Ni, though just to a certain level, depending on the fraction of eutectic phase in the alloy. The alloys were considered as a coarse two-phase system where a hardening effect is caused by load transfer to the harder phase, which requires a certain connectivity/contiguity of the latter. The paper describes the extent of contiguity of the eutectic as well as the hard silicon and Al₃Ni-phases within the eutectic, and discusses their contribution to an enhanced strength of Al-Si alloys at elevated temperatures.