富铈混合稀土对压铸AZ81合金组织和性能的影响

Effects of Cerium-rich Mischmetal on Microstructures and Mechanical Properties of Die-cast AZ81 Alloys

为开发铸造性能优越、成本低廉、中温性能略有改善,并能满足摩托车曲轴箱服役环境的新型镁合金提供材料基础,通过往AZ81合金中添加富铈混合稀土,考查稀土对压铸镁合金AZ81组织和性能影响.结果表明:少量加入稀土能起晶粒细化和固溶强化作用;随加入量增大,稀土以晶界和穿晶条状脆性相存在,对合金强度的损伤作用大于强化作用.因此,压铸AZ81的常温和150℃抗拉强度和屈服强度随稀土加入量的增加先略有提高,然后持续降低;室温延伸率随稀土加入量增加而连续下降,对150℃温度下的延伸率无明显影响;但富铈混合稀土的加入显著提高合金的蠕变抗力.

In order to research and development a new type of Mg-alloys with good casting processes property, low cost, the medium temperature property a few improvement and can be used as Motorcycle Crankcase, different additions of cerium-rich mischmetal have been put in AZ81. The effects of cerium-rich mischmetal （MM） on microstructures and mechanical properties of the die-cast magnesium alloys are investigated. The results indicate that a small amount of Ceriumrich Mischmetal addition refine microstructure and increase mechanical properties via solution strengthening. With increase of Mischmetal addition, Al-RE phases distributing along the grain boundary and within the grain in the forms of thick brittleness strip plays a detrimental role in mechanical properties. Consequently, with the addition of MM the tensile strength and yield strength of the alloy increase slightly at first, and then decrease continuously. The elongation of the alloys decreases at ambient temperature, but remains unchanged at 150℃. However, the addition of MM improves the creep behavior of the alloy significantly.