Using friction stir processing to produce ultrafine-grained microstructure in AZ61 magnesium alloy

In order to obtain fine-microstructure magnesium alloys with superior mechanical properties, AZ61 alloy was processed by friction stir processing(FSP) combined with rapid heat sink. It is found that ultra fine-grained microstructure with average size less than 300 nm is observed in the resultant AZ61 alloy. The mean microhardness of the ultra-fine region reaches Hv120-130, two times higher than that of AZ61 substrate. All these results demonstrate clearly that under a cooling rate high enough, ultra-fine structure in AZ61 alloy with superior mechanical properties can be produced by one pass FSP via dynamic recrystallization.