A burnished and Al-alloyed magnesium surface with improved mechanical and corrosion properties

Highlights: • Burnishing treatment significantly refines Mg surface grains, resulting in a thick Al-enriched surface layer. • The burnished and Al-alloyed Mg surface layer contains large amounts of hard stable and passive Al-Mg intermetallic phases. • The burnished and Al-alloyed Mg surface with strong passivity is insusceptible to galvanic corrosion. • The burnishing and alloying technique may open up a cost-effective way to solve the galvanic corrosion in Mg applications. Magnesium (Mg) surface was mechanically burnished and then alloyed with aluminum (Al) by thermal diffusion. The grain-refinement by surface burnishing significantly facilitated the Al alloying and led to a thicker and more uniform Al-enriched surface layer which could be spontaneously passivated like an Al alloy in a corrosive environment and thus had significantly enhanced micro-hardness and corrosion resistance. As this burnished and alloyed surface is scratch-resistant, much nobler than Mg, and insusceptible to galvanic corrosion, this burnished alloying method may be employed to solve the most stubborn galvanic corrosion problem with magnesium alloys in engineering applications.