Mg-Al-Ce-Y基压铸合金的微观结构稳定性和力学性能

摘要

为进一步提高Mg-A1-RE基合金的力学性能,采用高压压铸技术制备Mg-3.0Al-1.8Ce-0.3Y-0.2Mn合金,并研究其微观组织、金属间相的热稳定性和合金的力学性能.结果表明:合金由细小的初生α-Mg枝晶和枝晶间的共晶组成.共晶中存在两种金属间相,即Al11(Ce,Y)3和Al2(Ce,Y),其中Al11(Ce,Y)3是主要增强相.研究还表明,Al11(Ce,Y)3的热稳定性是有条件限制的,在200℃时效800 h,它基本保持稳定,而在450℃时效800 h,绝大部分的Al11(Ce,Y)3发生相分解,转变为Al2(Ce,Y).添加Ce和Y后,合金强度在室温和200℃下得到明显的提高.合金性能的提高主要归因于Al11(Ce,V)3的形成对枝晶间区域的增强作用、晶粒细化的影响以及由Y原子造成的固溶强化.%With the aim to further improve the mechanical properties of Mg-Al-RE-based alloy,Mg-3.0Al-1.8Ce-0.3Y-0.2Mn alloy was prepared by high-pressure die-casting technique.The microstructure,thermal stability of intermetallic phases and mechanical properties were investigated.The results show that the alloy is composed of fine primary α-Mg dendrites and eutectic in the interdendritic regions.The intermetallic phases in eutectic are Al11(Ce,Y)3 and Al2(Ce,Y) with the former being the dominant one.The thermal stability of Al11(Ce,Y)3 is conditioned.It is basically stable at temperature up to 200 ℃ within 800 h,while most of the Al11(Ce,Y)3 intermetallics transform to Al2(Ce,Y) at higher temperature of 450 ℃ for 800 h.The alloy exhibits remarkably improved strength both at room temperature and 200 ℃,which is mainly attributed to the reinforcement of dendrite boundaries with Al11(Ce,Y)3 intermetallics,small dendritic arm spacing effect as well as the solid solution strengthening with Y element.