The Corrosion Behavior Of AZ31 Magnesium Alloy In Simulated Human Body Environment

Due to the suitable mechanical property,biocompatibility and biodegradability, magnesium alloys are promising in the development ofbio-absorbable orthopedic implants for interventional therapy and bone tissue engineering.However,a rapid corrosion rate resulted form the intrinsically active response of magnesium alloys to chloride-containing blood plasma and human body fluid remains the problem.Subsequently,a better understanding of the interaction between magnesium alloys and human body environment is the prerequisite to lower the corrosion rate.To this end,the corrosion behavior of AZ31 magnesium alloy in Hank's simulated body fluid(SBF) was studied in the current research.The dynamic corrosion rate with time was determined by a normal device designed to measure the hydrogen evolution accurately.The results show that chloride is the dominant factor in the corrosion process of AZ31.Moreover, the effects of other radicals in SBF were also investigated.The corrosion morphology was studied by optical microscope,finding that the corrosion of AZ31 in SBF was facilitated by chloride in a non-uniform manner called filiform corrosion.The morphological trait of filiform corrosion was studied by scanning electron microscope(SEM).This article also investigated the microstructure and phases by metallographic microscope and XRD;the corrosion rate by weight loss method;corrosion morphology by scanning electron microscope;polarization behavior by dynamic potential polarization.Based on the experiment the corrosion behavior of deformed and as cast AZ31 magnesium alloy was compared,and the magnesium alloy's corrosion mechanism was discussed.The results showed that:AZ31 deformed magnesium alloy's corrosion resistance was better than AZ31 as cast magnesium alloy at the beginning stage due to the second phase whose potential was higher than the matrix.After a period of time,AZ31 as cast magnesium alloy's corrosion resistance was better than the AZ31 deformed magnesium alloy.With the corrosion time's increasing,the substrate a of AZ31 as cast magnesium alloy sample surface were constantly dissolved,the percent of Al-rich phase on the surface of the sample was increasing,forming a corrosion resistant Al-rich layer of the network structure as a protection layer impeding the corrosion. Clearly,the consecutive distribution of phase can improve the corrosion resistance of AZ31 magnesium alloy. The plastic deformation distribution in expended stent was simulated by finite element analysis methods.The results showed that the inside part of the supporting strut was suffered more sever deformation than the outside part.Moreover,the inside of supporting strut was corroded more rapidly than the outside part.As a result,the heterogeneous distribution of plastic deformation in stent was responsible for the heterogeneous corrosion condition, resulting in the early lose of effectiveness of bio-degradable magnesium stent.