Mechanical behavior and microstructure of a thermally stable bulk nanostructured Al alloy

A commercial aluminum alloy, 5083, was processed using a cryomilling synthe sis approach to produce powders with a nanostructured grain size. The powde rs were subsequently degassed, hot isostatically pressed, and extruded. The grain size at each processing step was measured utilizing both X-ray diffr action and transmission electron microscopy (TEM). The mechanical propertie s of the n-5083 extruded material were determined utilizing ASTM E8-93, Sta ndard Test Methods for Tension Testing of Metallic Materials. This processi ng technique was found to produce a thermally stable nanostructured aluminu m alloy which maintained an average grain size of 30 to 35 nm through sever al processing steps up to 0.61 T-mp. The thermal stability was attributed t o Zener pinning of the grain boundaries by AIN and Al2O3 particles and solu te drag of numerous atomic species. The nanostructured 5083 was found to ha ve a 30 pet increase in yield strength and ultimate strength over the stron gest commercially available form of 5083, with no corresponding decrease in elongation. The enhanced ductility is attributed to the presence of a few large, single-crystal aluminum grains acting as crack-blunting objects.