Al和Ce的含量对Mg-Al合金组织的影响

Effect of Al- and Ce-content on Microstructure of Mg-Al Magnesium Alloys

研究了Al和Ce的含量对Mg-Al-Ce合金组织的影响以及第二相的演变规律,进行热力学计算分析探讨了合金化合物的形成规律及其作用。结果表明:添加适量的Ce对Mg-Al合金有细化晶粒的作用,当Al的添加量(质量分数,下同)为2.5%、Ce的添加量为2%时晶粒最小,为280μm。数据拟合结果表明,Al含量为6.4%~7%、Ce含量为1.6%~2%为最佳添加量,可使晶粒尺寸减小到160μm。随着Al、Ce含量的变化合金中优先生成Al4Ce相,在凝固过程中细小的Al4Ce化合物吸附在α-Mg晶粒周围形成片层状共晶,阻碍α-Mg晶粒的长大从而细化合金晶粒。

The effect of Al-and Ce-content on the microstructure and the evolution of second phases of Mg-alloys Mg-Al-Ce were investigated, while the relevant mechanism related with the formation of intermetallic phases and the grain refinement of alloys were analyzed thermodynamically. The results show that the addition of certain amount of Ce can effectively refine the grain size of Mg-Al alloys, while with the addition of 2.5% Al and 2% Ce, the grain size could be decreased from 1000 μm for pure Mg to 280 μm for the alloy Mg-Al-Ce. According to the data fitting of experimental results the optimum content（in mass fraction） of Al and Ce were 6.4%~7% and 1.6%~2% respectively,the grain size can be reduced to 160 μm. Results of experiment and thermodynamics calculation indicated that intermetallic compounds of Al-Ce have smaller formation enthalpy than that of Mg-Ce and Mg-Al, and the phase Al_4Ce preferentially formed in the melts while the small intermetallic compounds Al_4Ce adsorbed on the α-Mg grains leading the formation of lamellar eutectic, which can hindered the growth of α-Mg grain and so as to refined the grains.