Research On Microstructures And Properties Of Squeeze Casting WE43 Bio-magnesium Alloy

Magnesium alloys have recently attracted much interest in biomedical applications due to good biocompatibility and natural degradation in the body.However,the mechanical properties and corrosion resistance of magnesium alloys are poor,which affect the clinical application of magnesium alloys.In this study,WE43 magnesium alloy ingots were prepared by squeeze casting.The microstructures and properties were improved by heat treatment.In order to study the corrosion resistance of WE43 magnesium alloys of as-cast,squeeze casting,T4 treatment and T6 treatment,corrosion tests such as weight loss test,pH test and electrochemical test were carried out in simulated body fluids?SBF?.The results showed that the grain size of WE43 magnesium alloy was reduced to27.89?m and the mechanical properties of the alloys were improved after squeeze casting.When the pressure ratio was 604MPa,the tensile strength,yield strength,elongation and hardness of the alloy were 181MPa,152MPa,7.62%and 68.7HBW,respectively.The morphology of the second phase was changed by squeeze casting.The coarse lamellar Mg-Y-Nd phases were fractured and refined,and distributed uniformly along grain boundaries with thin strips.The strip Mg-Y-Nd phases and granular Mg₂₄Y₅ phases gradually entered the matrix after solution treatment of WE43 magnesium alloy by squeeze casting,and a small amount of granular Mg₂₄Y₅ phases remained in the matrix.It was found that the strength and elongation of the alloy increased first and then decreased with the solid solution time.The strength and elongation reached the maximum value after solution treatment for 6h.The tensile strength,yield strength,elongation and hardness of the alloy reached 192MPa,157MPa,10.05%and 58.1HBW,respectively.However,the hardness gradually decreased.After aging treatment of the alloy treated with solid solution for 6h,the fine granular Mg₂₄Y₅phases and the Mg-Y-Nd phases were gradually precipitated along the grain boundaries,the strength and hardness of the alloy were significantly improved.The tensile strength,yield strength and hardness of the alloy were 297MPa,280MPa and 94.3HBW after aging treatment for 14h,respectively.Compared with no-aged state,the tensile strength,yield strength and hardness of the alloy increased by 54.69%,78.34%and 55.10%,respectively.But the elongation of the alloy gradually decreased with the aging time.Corrosion resistance of WE43 magnesium alloy in different condition were investigated.The weight loss test showed that the average corrosion rate of WE43 magnesium alloy with solution treatment for 6h was 0.4507mm/year.PH test showed that with the increase of soaking time,the pH of the soaking solution gradually increased and then stabilized.The pH value of the soaking solution of gravity casting alloy was the highest,reached 11.14,and the pH value of the soaking solution of alloy with solution treatment for 6h was the lowest.It was 10.43.The electrochemical impedance spectroscopy showed that the radius of high-frequency capacitance arc resistance of alloy with solution treatment for 6h was the largest.The corrosion of gravity casting and squeeze casting alloy mainly occurred along the grain boundaries.It was found that corrosion grooves were formed and gradually propagated along the grain boundaries.After solution treatment for 6h,the corrosion of the alloy mainly occurred and uniformly propagated in the grains with corrode spot and pitting.The corrosion of the alloy was occurred and propagated in the grains and grain boundaries with corrode spot and pitting after solution treatment for 6h and aging treatment for 14h.Corrosion experiments showed that the corrosion resistance of WE43 magnesium alloy increased progressively as follow:as-cast<squeeze casting<T6 treatment<T4 treatment.