1st Paragraph: High-energy ball milled (HEBM) alloys exhibit superior strength and corrosion resistance [1–5] to commercial alloys. The simultaneous improvement in properties has been attributed to the combined effect of suitable alloying elements and microstructural features such as nano-sized grains, extended solid solubility and fine uniformly distributed secondary phases [6–8]. These microstructural features exist in a metastable state, therefore, providing enough thermal energy will promote the formation of thermodynamically stable structure inverting the benefits of the nanostructured alloy . Formation of coarse intermetallics decreases corrosion resistance by promoting micro-galvanic interactions whilst providing little strength. Additionally, as the solute in the matrix depletes the difference in electrochemical potential becomes larger, which further deteriorates its resistance to localized corrosion. Moreover, impairments in strength can also result from exposure to high temperatures by recrystallization, grain growth and relieved internal stress. The decomposition of a super saturated solid solution to minuscule and uniformly distributed intermetallics is expected to increase the strength of an alloy and is known as precipitation strengthening, as observed in age-hardenable alloys.
Authors: J. Esquivel, M.G. Wachowiak, S. O’Brien, and R.K. Gupta
Keywords: Aluminum, Mechanical Alloying, Thermal Stability