The effects of the alloy elements on microstructure and mechanical properties of magnesium

Sometimes for some reasons magnesium alloys are alloyed with some elements such as calcium, strontium, zirconium, cadmium, indium, silver, silicon, beryllium, lithium, thorium, stannum. In this study, the effects of In and Cd addition varied between 0,2-0,8 wt % on the microstructure and mechanical properties of AZ91 magnesium alloy have been examined. The reasons of adding these elements into AZ91 alloy are that there are almost no research in the literature about the effects of In and Cd addition on the metallurgical and mechanical properties of AZ91 magnesium alloy and it was also thougt that these elements might have the same effects like Al and Zn on AZ91 alloy because In is in the same group with Al, Cd is in the same group with Zn in the periodic table. In the first step of the experimental study, gravity casting process was used to cast AZ91 alloy by adding In and Cd element at 700°C. After that magnesium alloy ingots were processed at suitable sizes for metallurgical and mechanical tests. In the second step of the experimental study, for the metallurgical experiment, the optic microscobe and SEM-EDS were used to investigate the microstructure of AZ91 alloy and XRD was used to determine the phases of AZ91 alloy. The results showed that as the In and Cd are added into AZ91 alloy, the intermetalic phase (Mg17Al12) is refined. It was obseved that increasing Cd content increased the grain sizes of the alloy and increasing In element decreased the grain sizes of the alloy. In the third step of the experimental study , It was observed that increasing the amount of In and Cd addition into AZ91 alloy increased the hardness by 5%-10% of AZ91 alloy respectively. But there was no significant changes for yield strength of AZ91 alloy by increasing the amount of Cd element. However, increasing the amount of In element increased the yield strength of the alloy by 5%-10% respectively. It was also observed that there was no significant changes for the shortening of AZ91 alloy.