铈对AZ91D镁合金组织和力学性能的影响

Effect of Ce on Microstructure and Mechanical Property of AZ91D Magnesium Alloy

利用光学显微镜、X射线衍射和扫描电镜等分析研究了含铈AZ91D镁合金(0.26%Ce、0.69%Ce、0.93%Ce)的显微组织及相组成,并对其室温力学性能进行了测试,同时与不含铈AZ91D镁合金的组织和力学性能进行了比较。结果表明,当加入0.69%Ce时,合金铸态组织得到明显细化,网状β相呈弥散的粒状分布于晶界上,同时有大量的针状物Al4Ce相出现;而当加入0.93%Ce时,合金的铸态组织没有细化现象,反而较AZ91D-0.69%Ce的组织有粗化的趋势,且针状化合物长大成杆状。适量稀土Ce可以改善合金的力学性能,当Ce含量为0.69%时,合金的抗拉强度、屈服强度、伸长率及硬度分别比AZ91D镁合金提高15.8%、8.7%、140%及15.7%,其综合力学性能达到最佳。分析了Ce对合金的综合强化机理。

The microstructure and phase composition of AZ91D magnesium alloys with the different additions of Ce were studied by optical microscope（OM）, X-ray diffraction（XRD） and scanning electron m icroscope（SEM）, the mechanical properties at room-temperature were tested, and the microstrucutre and mechanical properties were compared between the alloys with and without the addition of Ce. The results show that the as-cast microstructure of AZ91D magnesium alloy with addition of 0.69wt% Ce is refined obviously, reticular β phase is distributed dispersedly on grain boundary and a large number of acicular Al4Ce appear. However, the as-cast microstructure of the alloy AZ91D magnesium alloy with addition of 0.93 wt%Ce is no refined, but has a coarsening trend when combined with that of AZ91D magnesium alloys with the addition of 0.69 wt% Ce and the acicular compound become rodlike structure. The appropriate Ce addition can improve the mechanical properties of AZ91D magnesium alloy, the tensile strength,yield strength,elongation and hardness of the alloy with the addition of 0.69wt%Ce are increased by 15.8%, 8.7%, 140% and 15.7% respectively when compared with those of AZ91D magnesium alloy, and the combined mechanical property is the best. In addition, the strengthening mechanism of AZ91D magnesium alloy with the addition of Ce is discussed as well.