Study On The Microstructures And Corrosion Behaviors Of AZ81 Magnesium Alloys With Rare Earths

Based on the major compositions of AZ81 magnesium alloy, new magnesium alloys were prepared by adding different contents of rare earths into AZ81 magnesium alloy. Mechanical properties and corrosion resistance of magnesium alloy in the simulated human body fluid were improved by heat treatment. The microstructures and morphologes of the prepared magnesium alloys were analyzed by methods of metallographic analysis, SEM, EDS, XRD, mechanical properties testing and electrochemical corrosion testing. The morphology and distribution of intermediate compounds were studied. The mechanisms of rare earths improving the corrosion resistance of magnesium alloy were discussed. The optimized alloy elements were determined by the experiment results. The experiment results can be referenced for the application of magnesium alloys in the field of biomedical materials.The size of grains can be refined and the mechanical properties can be improved by adding rare earths La or Gd in the AZ81. On the other hand, the numbers of thin lamellarβ-phases are increased on the grain boundaries. The corrosion behavior was retarded byβ-phase, hence, the corrosion resistance of magnesium alloy was increased. After the annealing heat treatment, the compositions were distributed homogeneously, and the number of precipitatedβ-phase was decreased. The eutectic structures were decomposed, which reduced tendency of extending of intergranular cracks. However, the corrosion resistance of magnesium alloys was decreased. After the T6 heat treatment, a lot ofβ-phases were precipitated, and the continuously distributedβ-phases formed the corrosion barriers. Therefore, the corrosion resistance of magnesium alloys increased.