The effects of ECAP, Mn and Ca elements on the microstructure and corrosion properties of magnesium alloys were investigated

Abstract

In this study, through reasonable composition design, three elements of Zn, Mn and Ca, which are harmless to human body, were selected for alloying magnesium. The effects of ECAP treatment on the microstructure and corrosion properties of Mg-4Zn-1Mn-0Ca, Mg-4Zn-1Mn-0.2Ca and Mg-4Zn-0Mn-0.2Ca alloys were studied. The corrosion mechanism of Mg-Zn-Mn-Ca alloys with different components in Simulated. Body fluid (SBF) was analyzed by weight loss method and electrochemical test. The grains and the second phase were refined by Equal Angular Channel Pressing (ECAP). It was found that after 8 ECAP deformations, the microstructure of the alloy was refined and more uniform than that of the extruded alloy. The corrosion resistance of the Mg-Zn-Mn-Ca alloy after ECAP deformation in simulated body fluids was studied by electrochemical testing techniques, immersion experiments and observation of the microstructure and morphology of corrosion products. The relationship between microstructure characteristics, the behavior of the magnesium metal matrix and the properties of corrosion products was revealed. The results show that the microstructure of the alloy is refined and the corrosion resistance is improved with the increase in extrusion passes in the SBF solution. The corrosion resistance of magnesium alloy after 8 ECAP deformation is the best, showing small Icorr and large Rt. With the extension of the soaking time, the surface of the alloy will form a passivation film, which will protect the matrix and avoid further corrosion of the alloy. It is found that in SBF, the corrosion of the alloy surface is mainly pitting, which indicates that Ca²⁺, HCO^3- and HPO₄^2- in SBF can reduce the corrosion rate of magnesium alloy.