Abstract:Powder metallurgy was used to fabricate a bulk ultrafine grain size (UFG) Mg−3Al−Zn alloys. Nanocrystalline alloy powders with an average grain size of 45 nm were synthesized via ball milling of elemental powders of Mg, Al and Zn. The milled powders canned in Al containers were subjected to cold (at room temperature) or hot press (for 40 min at 633K), respectively, in a vacuum furnace. The sintered samples were extruded at 423 K to further solidify. The results show that the average grain size is 180 nm for the cold samples, and that is 600 nm for the hot samples. The cold-press alloys show a yield stress of 426 MPa. The high strength of UFG Mg is attributed to the fine grain strengthening mechanism resulting from the strong dependence of strength on the grain size for HCP metals. The consolidated samples of the cold-press and hot-press alloys have a final density of (1.777±0.006) and  (1.800±0.006) g/cm³, respectively.

Key words: Mg−3Al−Zn alloys; ultrafine grain; nanostructured powders; powder metallurgy