To obtain the refined electrodeposited nickel layer on AZ91D magnesium alloy,ultrasonic technology was applied in the processes of pre-treatment and electrodeposition.The phases of pre-treatment layer and the nickel coating were analyzed by X-ray diffractometry(XRD)and X-ray photoelectron spectroscopy(XPS),and the microstructure was observed by scanning electron microscopy(SEM).Then,the effects of ultrasonic dispersion on the microstructure of pre-treatment layer and the grain refinement of electrodeposited nickel layer were discussed.The results showed that the pre-treatment electrodeposited Cu-Sn layer with compact microstructure could be synthesized in alkaline copper-tin liquid with ultrasonic agitation,as a result,smooth and refined nickel coating formed on AZ91D magnesium alloy.On the other hand,preferred orientation in the coating decreased because of the refined grains.
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