Abstract
In the present paper, the influence of eutectic and intermetallic phases on cavitation resistance of Al-Si alloys was studied. In fact, Al-Si alloys are commonly used for the production of components, such as cylinders, pistons, pumps, valves and combustion chambers, which in service may incur in cavitation phenomenon. Samples of AlSi3, AlSi9 and AlSi9CuFe were characterized from the microstructural point of view. Hardness measurements were also performed. Subsequently, cavitation tests were carried out according to ASTM G32 standard and the erosion mechanism was examined by scanning electron microscope. It was found the both eutectic and intermetallic phases enhance cavitation resistance, expressed in terms of mass loss. Particularly, intermetallic particles with complex morphologies provide a positive contribution, exceeding that of other microstructural features, as grain size. The effect of T6 heat treatment was also evaluated. It was confirmed that the precipitation of fine strengthening particles in the Al matrix successfully hinders the movement of dislocations, resulting in a longer incubation stage and a lower mass loss for heat-treated samples in comparison with as-cast ones. Finally, the relationship between cavitation resistance and material hardness was investigated.
Highlights
Cavitation erosion is a mechanical damage that occurs when a component is in contact with a liquid in particular pressure conditions [1] since gas or vapor bubbles can nucleate and subsequently collapse due to pressure fluctuations in the fluid
Various studies are available in scientific literature regarding the characterization of cavitation erosion resistance of different alloys, as such as steels [6,7], cast irons [8], titanium and nickel alloys [3, 9,10]
Considering the erosion mechanism, under continuous exposure to cavitation, it is reported in scientific literature that the initial undulations of the exposed surface gradually develop into craters and material is lost by necking of the rims of the craters, flaking and dislodging of secondary phases [1, 3, 14, 19]
Summary
Cavitation erosion is a mechanical damage that occurs when a component is in contact with a liquid in particular pressure conditions [1] since gas or vapor bubbles can nucleate and subsequently collapse due to pressure fluctuations in the fluid. Numerous attempts to develop cavitation erosion models based on bulk mechanical properties [11,12,13] were performed in order to predict the erosion performance of metallic materials At this regard, some authors report the hardness as an indicator of the erosion resistance. Considering the erosion mechanism, under continuous exposure to cavitation, it is reported in scientific literature that the initial undulations of the exposed surface gradually develop into craters and material is lost by necking of the rims of the craters, flaking and dislodging of secondary phases [1, 3, 14, 19] It appears evident a dependency of cavitationerosion behavior on the alloy microstructure, not related to the heat treatment effect. In the present study, the cavitation resistance of different Al-Si alloys was evaluated in order to individuate the effect of Si and intermetallic particles on erosion resistance
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