Study on the Microstructures and Properties of Mg-3.5Al-RE Magnesium Alloys for Casting Engine
Mg-3.5Al-RE(RE=La,Ce,and Nd)and Mg-3.5Al-3Nd-0.9Zn-0.15Mn magnesium alloys were prepared by vacuum melting and die casting.The effects of rare earth elements,trace zinc and manganese elements on the phase com-position,microstructure,mechanical properties,thermal conductivity,and flow properties of die-casting magnesium alloys were studied.The results show that the die-cast Mg-3.5Al-RE magnesium alloys are mainly composed of α-Mg matrix,short rod like/fishbone like Al11RE3 or granular Al2RE phase,and the average grain size from large to small is:RE=La＞RE=Ce＞RE=Nd.The order of tensile strength and elongation of die-cast Mg-3.5Al-RE magnesium alloys from high to low is RE=Nd＞RE=Ce＞RE=La,and the order of thermal conductivity from high to low is RE=Ce＞RE=La＞RE=Nd.When RE=Nd,the die-cast magnesium alloy has the best comprehensive tensile properties.After adding Zn and Mn elements to Mg-3.5Al-RE magnesium alloys,the short rod/fishbone like Al11Nd3 phase in magnesium alloy is significantly less than that in die-cast Mg-3.5Al-3Nd magnesium alloy,and the size of the granular Al2Nd phase increases,the room temperature tensile property is e-quivalent to that of Mg-3.5Al-3Nd magnesium alloy,the microhardness increases by 7.02％,the number of thermal conduc-tivity systems decreases,and the flow length increases.
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