Effect Of Electric Pulses On Drawability And Corrosion Property Of Az31 Magnesium Alloy

Electric pulses were applied to the drawing process by improving the conventional mould. The effects of the electric pulses on the drawability of AZ31 magnesium alloy sheets were investigated.The drawability of hot-roll and twin-roll-cast AZ31 magnesium alloy sheets at room temperature was compared by tensile tests. They both bear poor drawability at room temperature, and the twin-roll-cast AZ31 magnesium alloy sheets have better drawability. Electric pulses were applied to the tensile tests. It is shown that the plasticity is enhanced and the values of n and r decrease with the increase of the pulse current. Therefore, the optimum pulse current exists in the drawing.It is shown in the simulative drawing tests that electroplastic effect exists with the electric pulses in the process of drawing. The lower resistance to deformation and better plasticity are obtained under the electric pulses. The temperature is still an important parameter. Twins play a significant role at low temperature, and dynamic recrystallized grains occur in the big deformed zone when the temperature is above 200℃. The drawing of square cups with the depth of 15mm is succeeded in 2.5min, with the energy consumption of 0.356 KWh. The energy consumption of electroplastic drawing is reduced compared with the conventional hot drawing. The electroplastic drawing is promised to become the new technique for manufacturing drawing products of magnesium alloys.The dynamic recrystallized grains occur at lower temperature with the electric pulses than conventional hot drawing, which results from the coupled actions of thermal and athermal effects induced by the electric pulses. The ductility of the AZ31 magnesium alloy is improved because of the favoring mechanism of non-basal glide and the effective mechanism of dynamic recrystallization.The corrosion behavior of AZ31 magnesium alloys subjected to cold rolling(CR) and electroplastic rolling(ER) respectively in the 3.5mass% NaCl solution was systematically investigated using electrochemical techniques as potentio-dynamic polarization curves, electrochemical impedance spectroscopy(EIS) as well as corrosion morphology observation and corrosion rate measurements. The corrosion behavior of ER AZ31 magnesium alloys subjected to high energy electric pulse treating(EPT) and conventional heat treating(CHT) respectively in 3.5mass% NaCl solution was studied as well. The results show that, under the same deformation strain, corrosion resistance of the as-ER samples is enhanced to some extent compared with that of as-CR specimens. This improvement in corrosion resistance is probably associated with the high ratio of recrystallization, the lower dislocation density and more stable corrosion film in the ER alloy. The corrosion resistance of as-ER sample is both enhanced after EPT and CHT, which is attributed to complete recrystallization and lower dislocation density after treatment. The initial corrosion rate of as-EPT sample with better mechanical properties is higher than that of as-CHT one, which results from the finer grain size leading to formation of more corrosion micro-cell.