(Invited) High Strength and Corrosion Resistant Light Alloys Via High-Energy Ball Milling

Abstract

The corrosion of metallic materials in a given environment depends on the microstructure stemmed from the concurrent influence of the composition, production route, thermomechanical processing, and service conditions. Microstructures and therefore the properties of the alloys produced via high-energy ball milling are known to be significantly different than that produced via conventional techniques even for the same alloy composition. Grain refinement, extended solid solubilities, formation of metastable phases, unique grain boundaries, super saturation of vacancies, high stored energy, increased diffusivities are some of the principle characteristics of the microstructure produced by the high-energy ball milling process. It has been shown recently that development of corrosion resistant light alloys (Al alloys and Mg alloys) is possible by high-energy ball milling in combination with the suitable alloying elements. Al- transition metal alloys have been produced by the high-energy ball milling and subsequent consolidation. X-ray diffraction analysis and scanning electron microscopy indicated significantly higher solid solubility of the transition metals in Al and nanoscale grain refinement. The cyclic potentiodynamic polarization tests revealed significant ennoblement of pitting and repassivation potentials of the high-energy ball milled Al -transition metal alloys. The Grain refinement < 100 nm and high solid solubility also increased mechanical strength- compressive yield strength exceeding 1 GPa. High-energy ball milling has been found capable of improving corrosion resistance and strength simultaneously. Mechanisms of the improved corrosion and mechanical properties of the high-energy ball milled alloys will be discussed.