Solidification Speed And The Influence Of Heat Treatment On The Microstructure And Mechanical Properties Of Magnesium Ap65 Anode

The object of this thesis is AP65magnesium alloy anode. The influences of solidification rate and heat treatment on micro structures and properties of AP65anode have been studied by X-ray diffraction, optical microscope, SEM, electrochemical tests, which can provide experimental basis for the preparation of magnesium anode with high electrochemical activity. The results are as follows:(1) The influences of solidification rate on microstructures and properties of AP65anode have been studied. The results show that grain refinement and the content of β-Mg17Al12phase decrease with the increasing of solidification rate. And the electrochemical activity decreases, but the corrosion resistance is improved at the same time. The sample prepared by iron mold with air-cooled has the best discharge behavior, the stable discharge potential is-1.619V at the current density of180mA·cm-2and the average corrosion rate is36.9mm·a-(2) The influences of homogenization annealing and aging on microstructure and properties of AP65anode have been studied. The results indicate that the dendritic segregation during solidification has been eliminated basically after homogenization at400℃for24h. β-Mg17Al12precipitates from the supersaturated matrix during aging treatment, samples show a better electrochemical activity. After aging at160℃for12h, the magnesium anode shows the best discharge behavior, the stable discharge potential is-1.616V at the current density of180mA·cm-2and the average corrosion rate is103.8mm·a-1.(3)The influences of annealing on microstructures and properties of AP65anode sheet have been studied. The results demonstrate that ecrystallization occurs in the hot-rolled sheet during annealing and complete recrystallization is obtained after annealing at300℃for1h. After annealing at300℃for80min, the magnesium anode sheet shows the best discharge behavior, the stable discharge potential is-1.618V at the current density of180mA·cm-2and the average corrosion rate is38.2mm·a-1. (5) The activity behaviors of AP65anode and the activity mechanism of Pb have been studied. The results show that pitting corrosion occurs in the initial stage of discharge and corrosion products peel off from the matrix, maintaining the activity of magnesium anode. Pb can deposit at the surface of anode during the discharge process, which is helpful to improve the activity.