Abstract
The microstructure and mechanical properties of various binary ultra-finegrained (d~200 nm) Al-Mg alloys is reported. The composition of alloys spans 0 wt.% Mg (pure Al) to 10.5 wt.% Mg (exceeding significantly the solubility limit). Powders are blended and mechanically alloyed during cryogenic milling in liquid nitrogen to obtain nanocrystalline structures. After cryomilling, powders are hot vacuum degassed and consolidated via hot isostatic pressing and extrusion. Local-electrode atom-probe tomography, X-ray diffraction, and electron microscopy are used with the goals of understanding microstructural evolution as a consequence of the various processing stages and Mg content. Alloys with the highest amounts of Mg exhibit strong Mg segregation to grain boundaries. The impact of this heterogeneous Mg distribution on microstructure and mechanical behaviors is discussed in the context of measured tensile and microhardness properties as a function of thermal exposure.