In-Situ Al-Mg Alloy Base Composite Reinforced by Oxides and Intermetallic Compounds Resulted from Decomposition of ZrW2O8 during Multipass Friction Stir Processing

Abstract

In the presented work, the effect of friction stir processing admixing the zirconium tungstate ZrW2O8 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-ZrW2O8 underwent the following changes: (i) high-temperature transformation into metastable β’-ZrW2O8 and (ii) decomposition into WO3 and ZrO2 oxides followed by the formation of intermetallic compounds WAl12 and ZrAl3. 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 Al2O3, ZrO2, β’-ZrW2O8 and intermetallic compounds such as WAl12 and ZrAl3. Potential applications of the above-discussed composites maybe related to their improved tribological characteristics, for example in aerospace and vehicle-building industries.

Microstructural Aspects of the Fabrication of Al/Al2O3 Composite by Friction Stir Processing

“…Specifically, a wide range of composites was successfully produced using a variety of both reinforcing particles and matrix aluminum alloys. The reinforcing elements typically comprise SiC [ 8 , 9 , 10 , 11 , 12 , 13 , 14 , 15 ] or Al 2 O 3 [ 11 , 16 , 17 , 18 , 19 , 20 , 21 , 22 , 23 , 24 , 25 ] phases but may also involve other particles [ 26 , 27 , 28 , 29 , 30 , 31 , 32 , 33 ]. On the other hand, the matrix materials included the 1xxx [ 8 , 9 , 16 , 29 ], 2xxx [ 20 , 21 , 22 ], 5xxx [ 11 , 13 , 27 , 30 , 32 , 33 ], 6xxx [ 12 , 17 , 23 , 31 ], and 7xxx [ 10 , 26 ] series of aluminum alloys.…”

Modeling Wear and Friction Regimes on Ceramic Materials with Positive and Negative Thermal Expansion

“…The well-known, easily available, and widely used NTE material ZrW 2 O 8 [21], with CTE = −10 −5 K −1 , comparable in modulus with that of metals. This NTE material was used for preparing metal matrix [22,23] and ceramic composites [24,25]. However, the thermal stability of ZrW 2 O 8 is not high and α-ZrW 2 0 8 with high NTE transforms into β-ZrW 2 O 8 with low NTE at ~670 K and then decomposes at ~1050 K [26].…”

“…However, the thermal stability of ZrW 2 O 8 is not high and α-ZrW 2 0 8 with high NTE transforms into β-ZrW 2 O 8 with low NTE at ~670 K and then decomposes at ~1050 K [26]. Such an instability may interfere not only with fabricating composites [27][28][29] but also strongly limits its application under conditions of intensive frictional heating [23].…”