An investigation of microstructural background for improved corrosion resistance of WE43 magnesium-based composites with ZnO and Cu/ZnO additions

Abstract

In this research, WE43-based nanocomposites were fabricated by addition of nano- and micro-sized particles of ZnO and Cu/ZnO, followed by friction stir processing (FSP). In addition to the effect of the size of additives, the effect of geometry of the particle insertions, groove and holes, on the evolution of microstructure and corrosion properties of Mg-based composites were studied. The grain size of the matrix of the fabricated composite was reduced after FSP. In addition, significant fragmentation and re-distribution of secondary phase particles occurred which resulted in size reduction, increased density and improved uniformity of the particles. Corrosion behavior of the composite was assessed by scrutinizing potentiodynamic polarization, electrochemical impedance spectroscopy, cyclic polarization and immersion tests. It was found that the corrosion mechanism of Mg-based nanocomposite samples was a combination of pitting and uniform corrosion. Furthermore, the rate of electrochemical corrosive reactions reduces by performing FSP and addition of particles. The composite fabricated using hole insertion and nano-sized particles showed a more uniform distribution of additives resulting in higher corrosion resistance in comparison with groove insertion. In addition, fabricated composite sample with Cu/ZnO particles presents the highest anti-corrosion properties. • A new Mg-based composite with ZnO and Cu/ZnO powders as reinforcing factors is developed by friction stir processing (FSP). • A composite with refined grains, redistribution of secondary phase particles and uniform distribution of ZnO and Cu/ZnO powders is fabricated. • Reduction of grain size and redistribution of secondary phase particles has a remarkable positive effect on improvement of corrosion resistance . • Because of presence of ZnO and ZnO particles, corrosion resistance of resultant composite is improved and localized corrosion is reduced. • Improved biocompatibility is observed due to the positive influences of ZnO and Cu/ZnO particles.