Influence of microstructure and strengthening mechanism of AlMg5-Al2O3 nanocomposites prepared via spark plasma sintering

In the present study, powder metallurgy processed unmilled AlMg5 (AlMg5-UM), milled AlMg5 (AlMg5-M), and milled AlMg5-0.4 vol.% Al2O3 (AlMg5-0.4Al(2)O(3)) nanocomposite were successfully spark plasma sintered at 550 degrees C. The microstructural analysis of spark plasma sintered AlMg5-UM revealed equi-axed grains with average size of 20 +/- 5 mu m. The microstructural analysis of spark plasma sintered AlMg5-M and AlMg5-0.4Al(2)O(3) revealed a bimodal grain structure with both fine-coarse grains of size 700 nm-8 mu m and 300 nm-8 mu m, respectively. The spark plasma sintered AlMg5-UM exhibited a yield strength (YS) of 132 +/- 3 MPa, ultimate tensile strength (UTS) of 296 +/- 2 MPa and % elongation (% El) of 22 +/- 2 comparable to the conventional Al 5083 alloy-O temper (YS of 145 MPa, UTS of 281 MPa and % El of 16). The spark plasma sintered AlMg5-M and AlMg5-0.4Al(2)O(3) exhibited YS of 242 +/- 9 MPa and 274 +/- 5 MPa, UTS of 376 +/- 4 MPa and 417 +/- 8 MPa and % El of 19 +/- 1 and 10 +/- 1, respectively. The lower strength (YS and UTS) of AlMg5-UM can be ascribed to its coarse grains. Among the milled samples, the AlMg5-0.4Al(2)O(3) composite exhibited high strength and it can be ascribed to its fine grain size (Hall-Petch effect), higher dislocation density and Orowan strengthening effect due to Al2O3 reinforcements. (C) 2016 Elsevier Ltd. All rights reserved.