Tribological properties improvement of conventionally-cast Al-8.5Fe-1.3V-1.7Si alloy by multi-pass friction stir processing

The effect of multi-pass friction stir processing (FSP) on the tribological properties of conventionally-cast Al-8.5Fe-1.3V-1.75i (FVS0812) alloy was investigated. The pin-on-disk dry sliding wear tests were conducted at room temperature under the applied pressures of 0.25, 0.50, and 0.75 MPa. The results showed that FSP substantially refined and improved the distribution of coarse theta-Al13Fe4 platelets and alpha-Al-12(Fe, V)(3)Si intermetallics in the microstructure of alloys and eliminated the intermetallic-related defects. Consequently, the mechanical properties of the alloys, especially their ductility, were improved, which enhanced the stability of the protective tribolayer formed on their worn surfaces. According to the wear test results, the FSPed samples showed improved tribological properties especially at the higher applied pressures. For instance, at the applied pressure of 0.75 MPa, the wear rate and average friction coefficient of four-pass FSPed sample were lower than those of the base as-cast sample by 97% and 52%, respectively. SEM examination of the worn surfaces and wear debris also demonstrated that the wear mechanism changed from severe delamination/abrasion and microcracking of the tribolayer in the as-cast samples to mild delamination/abrasion and minor plastic wear in the FSPed samples.