Effects of Heavy Rare Earth Gd on Solidification Microstructure and Melt Fluidity of AZ91D Magnesium Alloy AITranslate

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Chinese Library Classification Number:TG146.453[一般工业技术]

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In order to investigate the effect of heavy rare earth on the solidification microstructure and melt fluidity of magnesium alloy,AZ91D magnesium alloys with 0.3%,0.6%,0.9%,1.2%and 1.5%(mass fraction)Gd were prepared.The phase identification and morphology and composition analysis of the solidification microstructure of the alloys were carried out by XRD and SEM-EDS.The solidification interval and dendrite coherency temperature were determined via a dual-thermocouple technique.The melt fluidity was evaluated by a spiral sample mold,and the hardness of the alloys was measured by a Rockwell hardness tester.The results show that rare earth Gd can significantly refine both theα-Mg grains andβ-Mg₁₇Al₁₂phase.When the Gd content is 0.9%,the average grain size ofα-Mg is the smallest,which is 135.87μm.The rare earth phase Al₂Gd is mainly distributed along the grain boundary and blockily precipitated.The addition of an appropriate amount of rare earth Gd reduces the solidification interval and dendrite coherency temperature of the alloy,which greatly improves the melt fluidity.With the increase of Gd content,the hardness of the alloy increases first and then decreases,reaching a peak of 75.1 HRB at 0.9%Gd.This study can provide a theoretical basis for expanding the application of magnesium alloys and realizing the comprehensive utilization of rare earth resources.