| Abstract: | In this study AZ31B Magnesium alloy was pre-treated with surface mechanical attrition process (SMAT), for nanocrystallization, and subsequently plasma electrolytic oxidation was applied. Real-time imaging and microscopic investigation were used to study discharge events to reveal the pre-treatment effect on coating growth. SMAT processing developed a 100 nm nano-crystalline layer. Nano-crystallinity was verified by XRD and TEM studies which showed that treated area has crystalline size of about 30 nm. SEM studies revealed that in first minute number of discharges on nano-crystalline surface was 50% higher than microcrystalline surfaces. Number of discharge channels in both samples became nearly identical in longer treatment times. Most of the changes in growth rate are focused in first 2 minutes of coating. Calculations revealed that for pre-treated sample extracted volume of molten oxide through each discharges is significantly higher than non-treated sample while the number of discharges are less. However, number of discharges decline rapidly. While oxide layer grows the surface reactivity decreases. |
