The effects of the DC and AC magnetic fields on the phase composition, morphology and distribution of the ternary Al-Fe-Si alloy were investigated. The solidification structures of the alloy solidified with and without the application of magnetic fields were confirmed by DSC and structural measurements. The results showed that, Fe/Si ratio plays an important role in determining the reaction type, which in turn affects the phase composition, morphology. As for the alloy with the Fe/Si ratio 1.2, the elongated needle-like Al3Fe phase was the dominant phase in the dendritic regions with the minor amount of Chinese script-like α-AlFeSi. As for the alloy with the Fe/Si ratio 0.2, the Chinese script-like α-AlFeSi was the dominant phase, accompanied with a small amount of needle-like β-AlFeSi and granular Si. In these Al-Fe-Si alloys, the homogeneous distribution of the intermetallics formed in the interdendritic regions was achieved with the application of the DC magnetic field. However, the intermetallic phases were accumulated towards the sample center with the application of the AC magnetic field. This was attributed to the accumulation of the iron-containing cluster and silicon-containing cluster at the melt center. Furthermore, the amount of Chinese script-like α-AlFeSi was increased remarkably in the former alloy under AC magnetic field, while in the latter alloy, the amount of β-AlFeSi and Si was increased under AC magnetic field.
Ban Chunyan, Liu Na, Wang Na, Han Yi, Ba Qixian, Cui Jianzhong Key Laboratory of National Education Ministry for Electromagnetic Processing of Materials, Northeastern University, Shenyang 110004, China
An isothermal section of the Mg-Nd-Gd ternary system at 723 K was established by diffusion triple technique and electron probe microanalysis(EPMA). Mg3Gd and Mg3Nd form a continuous solid solution(Gd,Nd)3Mg, and a continuous solid solution(Gd,Nd)Mg is also formed between MgGd and MgNd. Mg7Gd, Mg5Gd, Mg2Gd, Mg41Nd5,(Gd,Nd)3Mg and(Gd,Nd)Mg are found in the ternary system. In these intermetallic phases, Mg7Gd has been reported to be a metastable phase in previous literatures. The solubilities of Mg, Gd and Nd in all the phases were detected. Furthermore, four three-phase equilibria, α(Mg)+Mg7Gd+ Mg41Nd5, Mg7Gd+Mg5Gd+Mg41Nd5, Mg5Gd+Mg41Nd5+(Gd,Nd)3Mg and(Gd,Nd)3Mg+(Gd,Nd)Mg+Mg2Gd, were identified in the isothermal section.采用三元扩散偶技术,利用电子探针成分分析,建立Mg-Nd-Gd三元系723 K的等温截面。Mg3Gd和Mg3Nd在三元系中形成连续固溶体(Gd,Nd)3Mg,MgGd和MgNd也形成连续固溶体(Gd,Nd)Mg。在三元系中出现的金属间化合物有Mg7Gd、Mg5Gd、Mg2Gd、Mg41Nd5、(Gd,Nd)3Mg和(Gd,Nd)Mg,其中Mg7Gd在以往的报道中认为是亚稳相。测量了Mg,、Gd和Nd在每相中的溶解度,发现在Mg-Nd-Gd三元系中存在4个三相平衡,它们分别是α(Mg)+Mg7Gd+Mg41Nd5,Mg7Gd+Mg5Gd+Mg41Nd5,Mg5Gd+Mg41Nd5+(Gd,Nd)3Mg和(Gd,Nd)3Mg+(Gd,Nd)Mg+Mg2Gd。
