Achieving ultrafine grain size in Mg-Al-Zn alloy by friction stir processing

Ultrafine-grained (UFG) microstructures with an average grain size of 100-300 nin are achieved in solution-hardened AZ31 Mg-Al-Zn alloy prepared by friction stir processing equipped with a rapid heat sink. The mean hardness of the UFG region reaches similar to 120H(v), which is more than twice as high as that of the AZ31 matrix. The grain refinement kinetics are analyzed and the results are self-consistent. (c) 2007 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.