Unique corrosion resistance of ultrahigh pressure Mg-25Al binary alloys.

Differing from as-cast and solid-solution alloys with coarse eutectic phases (Mg17Al12), a single-phase structure is attained in Mg-25wt.%Al alloy after ultrahigh-pressure solid-solution (USS, 800 oC, 4GPa). This USSed Mg-25wt.%Al sample exhibits a prominent age-hardening response due to the nano-scaled Mg17Al12 particles. Three testing methods confirm that USS-aged Mg-25wt.%Al alloy shows good corrosion resistance, which overwhelms the majority of Mg-based alloys reported so far, near to high purity Mg. The main reason is attributed to the formation of Al-rich oxide layer, wherein residual stress and pitting corrosion are eliminated. It provides a new avenue for developing corrosion resistant Mg alloys