Ce和Mg-Al_4C_3中间合金细化AZ31B镁合金的组织

Effects of Mg-Al_4Ce_3 Master Alloy and Ce on Microstructural Refinement of AZ31B Magnesium Alloy

采用SEM、EDS和XRD等测试手段,研究稀土元素Ce和Mg-50Al4C3中间合金对AZ31B镁合金显微组织的细化效果。结果表明,加入0.5%的Al4C3可显著细化AZ31B镁合金的枝晶组织和晶粒尺寸;添加0.5%的Al4C3和0.3%的Ce使合金的枝晶组织和晶粒尺寸进一步细化,α-Mg的平均晶粒尺寸由基体合金的280μm降至约50μm,同时,β相由连续网状转变为不连续的网状和细小的粒状,且产生新相Al4Ce。通过能谱分析及面错配度计算证实,Al4C3可作为初生α-Mg晶粒的良好异质核心。加入稀土元素Ce引起合金成分过冷的增加,从而能够激活固/液界面前沿潜在的Al4C3形核,提高Al4C3的形核率。

Effects of Mg-50 Al4Ce3 master alloy and Ce on the microstructural refinement of AZ31B magnesium alloy were observed by SEM (scanning electron microscope),EDS (energy dispersive spectrum) and XRD (X-ray diffraction). The results reveal that dendrite and grain size in AZ31B magnesium alloy can be remarkably refined with 0.5% Al4Ce3,and it is further refined with 0.5% Al4Ce3 and 0.3% Ce mixed addition,in which average grain size of α-Mg is decreased from 280μm in matrix alloy to approximately 50μm,and β phase is converted from continuous network structure into discontinuous network structure and fine particle with generation of Al4Ce phase. Based on the analysis of EDS and calculation of the planar mismatch between Al4Ce3 anf Mg,Al4Ce3 particles can be acted as the heterogeneous nuclei of primary α-Mg phase. Ce can result in the increase of constitutional undercooling of alloy,which can activate potential Al4Ce3 to form nucleation at solid-liquid interface front to increase the nucleation rate.