GRAIN REFINEMENT TECHNIQUES TO REDUCE BIODEGRADATION RATE OF MAGNESIUM ALLOY AS A POTENTIAL BIODEGRADABLE IMPLANT MATERIAL: A REVIEW <s> METHODS <s> Abstract Magnesium alloys have got extensive attention as biodegradable implant materials due to their biodegradability in the physiological environment and similar elastic modulus to natural bone. But their poor corrosion resistance is a dominant problem that limits their clinical application due to the inhomogeneous distribution of the second phase. Nevertheless, after high pressure torsion (HPT) treatment, the second phase became nano-sized particles and distributed uniformly in grain interiors instead of along grain boundaries. The immersion tests indicated that the HPT-treated sample exhibited homogeneous corrosion resulting from the uniform distribution of the second phase. The results of the potentiodynamic polarization experiments showed that, compared with the as-cast alloy, the corrosion current density of the HPT-treated alloy decreased from 5.3 × 10 − 4 A/cm 2 to 3.3 × 10 − 6 A/cm 2 . <s> BIB001 </s> GRAIN REFINEMENT TECHNIQUES TO REDUCE BIODEGRADATION RATE OF MAGNESIUM ALLOY AS A POTENTIAL BIODEGRADABLE IMPLANT MATERIAL: A REVIEW <s> METHODS <s> Abstract In order to select a good cost-performance ratio magnesium alloy as anode material, the electrochemical properties of AZ31B magnesium alloy under different processing conditions were investigated by electrochemical workstation, optical microscope (OM), scanning electron microscopy (SEM) and energy dispersed spectroscopy (EDS). Extruded, rolled, cast-rolled and as-cast AZ31 magnesium alloys were prepared as the anode materials. The results show that under different processing conditions, the extruded alloy is the best cost-performance ratio anode material among the four alloys. It possesses the most negative equilibrium potential, the lowest corrosion current density and the smallest free corrosion rate indicating the highest electrochemical activity due to the uniform fine grains and the second phase. Its corrosiun products are loose, dispersing uniformly on the extruded anode surface, prone to falling off which decrease the polarization and increase the utilization of the anode. The electrochemical activity and the corrosion resistance of the rolled and the cast-rolled alloys are relatively low, compared with the extrude samples. Due to the coarse grains, as-cast defects and coarse second phase distributed along the grain boundaries, the as-cast alloy has unstable discharge curve and positive discharge potential. The corrosions of AZ31 magnesium alloy under different conditions are almost pitting corrosion. <s> BIB002
a) The experiment studying electrochemical performance of AZ31 magnesium alloy under different processing As This experiment was conducted by BIB002 ( 1) Where J is free corrosion rate, mA/cm2; m0 is initial mass and m1 is accurate mass of samples after self-corrosion test, mg; t is for time, s; S is area, cm2. Electrochemical impedance spectroscopy (EIS) was measured in the frequency range of 10-1~105 Hz. b) The experiment studying of homogeneous corrosion of high-pressure torsion treated Mg-Zn-Ca alloy in simulated body fluid Gao et. al. BIB001 experimented using the alloy with a chemical b) The experiment studying of homogeneous corrosion of high-pressure torsion treated Mg-Zn-Ca alloy in simulated body fluid There is great potential for the use of these grain refinement methods for further application in medical field.