In-Situ Al-Mg Alloy Base Composite Reinforced by Oxides and Intermetallic Compounds Resulted from Decomposition of ZrW 2 O 8 during Multipass Friction Stir Processing.

In the presented work, the effect of friction stir processing admixing the zirconium tungstate ZrW 2 O 8 powder on the microstructure, mechanical and tribological properties of the AA5056 Al-Mg alloy stir zone has been studied. The FSP resulted in obtaining dense composite stir zones where α-ZrW 2 O 8 underwent the following changes: (i) high-temperature transformation into metastable β'-ZrW 2 O 8 and (ii) decomposition into WO 3 and ZrO 2 oxides followed by the formation of intermetallic compounds WAl 12 and ZrA l3 . These precipitates served as reinforcing phases to improve mechanical and tribological characteristics of the obtained fine-grained composites. The reduced values of wear rate and friction coefficient are due to the combined action the Hall-Petch mechanism and reinforcement by the decomposition products, including Al 2 O 3 , ZrO 2 , β'-ZrW 2 O 8 and intermetallic compounds such as WAl 12 and ZrAl 3 . Potential applications of the above-discussed composites maybe related to their improved tribological characteristics, for example in aerospace and vehicle-building industries.