Influence of the dendritic microstructure and β-Al5FeSi phase on the wear characteristics in a horizontally solidified Al-7Si-0.4Mg-1.2Fe alloy

In this work an Al-7Si-0.4Mg-1.2Fe alloy (wt.%) was subjected to a horizontal solidification experiment using a water-cooled solidification device equipped with thermocouples to obtain temperature vs. time data which in turn allowed solidification thermal parameters, such as growth and cooling rates (V-L and T-R, respectively), to be determined. In turn, tribological behavior of samples with different secondary dendritic spacing (lambda(2)) and beta-Al5FeSi platelets length (beta(Fe)) were assessed by means of dry sliding wear testing performed in a rotating fixed ball machine, with wear volume and rate (W-V and W-R, respectively) being the two main investigated wear parameters. Quantitative metallography by optical and scanning electron microscopy along with energy dispersive X-ray spectroscopy enabled both as-cast microstructures and worn craters to be characterized. More significant variations in wear resistance of the investigated alloy were found for ranges of lambda(2) and beta(Fe) that lie within 12-20 mu m and 14-36 mu m, respectively, with the coarsening of the microstructure constituted by Al-rich primary phase dendrites surrounded by alpha-Al + Si +theta-Mg2Si + beta-Al5FeSi eutectic structures favoring reduced WV and WR values. For lambda(2) and beta(Fe) values higher than 24 and 48 mu m, respectively, both W-V and W-R stabilize assuming constant values that depend on the sliding distance. In addition to power type equations relating lambda(2) and beta(Fe) to V-L and T-R, mathematical expressions for variations of W-V and W-R with lambda(2) and beta(Fe) are also proposed. Finally, a comparative analysis with the literature is presented.

Automated summary

The Al-7Si-0.4Mg-1.2Fe alloy was studied through solidification experiments with different dendritic spacing and platelet length, showing significant variations in wear resistance within specific ranges. These variations were found to be related to the microstructure of the alloy and can be described by mathematical expressions relating to wear parameters.