A Simple Surface Treatment for Mg to Gain Enhanced Resistance to Corrosion and Corrosive Wear by Hammering Al Powder-Covered Mg Substrate

Mg is abundant in the earth crust and very attractive as a base metal of lightweight alloys for the transportation industry due to its high strength-to-weight ratio. However, Mg is prone to corrosion, which largely limits its widespread applications. Here, a very simple surface treatment method is demonstrated for enhanced resistance to corrosion and corrosive wear by hammering Al powder-covered surface of Mg with subsequent recovery treatment. Such treated surface is examined with X-ray diffraction technique for information on phases, nanocrystallization, thickness, and coverage of the Al layer. Structure of the Al layer and lattice imperfections are analyzed with transmission electron microscopy. Electrochemical behavior, corrosion, and corrosive wear of the treated surface are evaluated. It is shown that the treated surface is nanocrystalline with significantly increased resistance to corrosion and corrosive wear. The effect of recovery heat treatment on microstructure of the Al layer is particularly characterized and demonstrated to be essential for achieving high degrees of nanocrystallization and structure integrity through eliminating lattice defects generated during the hammering process, leading to a desired nanocrystalline structure with high stability and superior properties. Molecular dynamics simulation is also performed to gain an insight into the underlying mechanism.