As-cast microstructure and Sr-containing phases of
AZ31 magnesium alloys with high Sr contents
AZ31 magnesium alloys with high Sr contents
(1. National Engineering Research Center for Magnesium Alloys, Chongqing University, Chongqing 400044, China;
2. College of Materials Science and Engineering, Chongqing University of Technology, Chongqing 400050, China)
2. College of Materials Science and Engineering, Chongqing University of Technology, Chongqing 400050, China)
Abstract: The as-cast microstructure and Sr-containing phases in the AZ31 magnesium alloys with different Sr contents (0%, 0.3%, 2.5% and 5.0%, mass fraction) were investigated. The results indicate that after adding Sr to the AZ31 magnesium alloy, the dendrite/grain size is decreased, and with the Sr content increasing from 0 to 5.0%, the dendrite becomes finer, the dendrite morphology becomes more passive and the distribution of alloying phases at dendrite/grain boundary is dispersed. Furthermore, the morphology of the β-Mg17Al12 phase in the alloy with addition of 0.3%Sr changes from continuously irregular strip-like shape to discontinuously irregular strip-like shape and/or fine granule-like shape. At the same time, some lamella-like eutectic phases are found in the alloys with additions of 2.5% Sr and 5.0% Sr, and the lamella spacing in the alloy with addition of 5.0% Sr is finer. Adding high Sr content to the AZ31 alloy can bring the new ternary eutectic and/or divorced eutectic phase of Mg11Al5Zn4 in the alloy, and the Mg17Sr2 and Mg2Sr phases are formed in the alloys with additions of 2.5% Sr and 5.0% Sr.
Key words: magnesium alloy; AZ31 magnesium alloy; Sr-containing phase; Sr