Research on alloying technique of yttrium on AZ91D magnesium alloy

Effect of alloying techniques of dollop-like yttrium, as-cast and extruded Mg-Y master alloy in AZ91D magnesium alloy on microstructure and the efficiency of alloying was studied by optical microscopy, scanning electron microscopy, XRD and inductively-coupled plasma (ICP) spectroscopy. The as-cast AZ91D-1.2wt.%Y alloys were prepared and yttrium was added by different way at 750 degrees C. The results showed that the efficiency of alloying achieved less than 50% within 60 minutes when dollop-like yttrium was added. When yttrium was added by as-cast and extruded Mg-25wt. %Y master alloy, the efficiency of alloying was 71.3wt. % and 78.3wt. %, respectively. The efficiency of alloying was improved because the Mg-Y master alloy could melt easily down at casting temperature. The Mg-Y phases were formed in the Mg-Y master alloys. After the as-cast Mg-Y master alloy was extruded, the decrease in Mg-Y particle size and increase in the number of nucleating sizes for Mg led to the microstructure of the as-cast AZ91D-1.15wt. %Y alloy was refined.