Effect of Al2O3/Y2O3 in AA 7017 matrix nanocomposites on phase formation, microstructures and mechanical behavior synthesized by mechanical alloying and hot-pressing techniques

Mechanical alloying (MA-20 h) and hot pressing (HP-500 MPa, 400 degrees C, 60 min) were used to fabricate AA 7017, AA 7017 + 10 vol.% Al2O3, AA 7017 + 10 vol.% Y2O3, and AA 7017 + (5 vol.% Al2O3 + 5 vol.% Y2O3) nanocomposites. The effects of oxide addition on the microstructure (HR-SEM and HR-TEM), phase evolution (XRD) and mechanical behavior (hardness and compressive strength) were investigated. The microstructure of the samples exhibited grain refinement due to fracturing and severe plastic deformation during MA with homogeneous dispersions. Scherrer's and Williamson-Hall models were analyzed for the structural properties (crystal size, lattice strain and lattice parameter) variation on the powder and hot consolidated samples. The results of the mechanical properties showed that the hybrid nanocomposite exhibited higher hardness (296 +/- 1.87 VHN) and compressive strength (1047.5 +/- 2.96 MPa) along with the formation of MgZn2 and Al2Y precipitates, indicating a supersaturated solid solution. The precipitation and dislocation models play an important role in the strengthening mechanism.