Improved solidification structures and mechanical properties of Al-20wt% Sn alloys processed by an electromagnetic vibration technique
Improved solidification structures and mechanical properties of Al-20wt% Sn alloys processed by an electromagnetic vibration technique
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改进%20凝固%20结构%20和%20机械%20性能%20of%20Al-20wt%%20Sn%20合金%20加工%20by%20an%20电磁%20振动%20技术
DOI：
10.1016/j.msea.2022.144416
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发表时间：
2023
期刊：
影响因子：
--
通讯作者：
Inoue Eisaku
中科院分区：
文献类型：
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作者：
Tamura Takuya;Li Mingjun;Takahashi Koichi;Inoue Eisaku
Sn相在Al-Sn合金中的均匀分布有利于合金性能的提高。然而，该合金具有亚稳的不混溶间隙，导致通常铸造中的相宏观偏析。在本研究中，具有Al-20wt%Sn-1wt%Cu（以下简称为Al-20wt%Sn）的实际成分的合金在静磁场中凝固，当交流电流过合金时，电磁振动（EMV）被施加在凝固液体上。凝固组织进行了观察和表征的低熔点锡相。结果表明，当电磁振动频率为100 Hz时，Sn相可以细化并均匀分散在初生Al基体中，这与未施加电磁振动时凝固的连续Sn网络形成了对比。具有细Sn分散体的试样在拉伸试验中具有改善的伸长率。从组织形成和溶质分布两个方面探讨了定向凝固过程中施加电磁振动的凝固机理。初级Al固溶体相和周围液体之间的非耦合运动可以将Sn液膜分解成离散段，从而在最终凝固阶段形成孤立颗粒。同时，这种非耦合运动可以诱导强制流体流动，该强制流体流动可以搅拌熔体以使剩余液池中的溶质分布均匀化。在施加EMV时考虑了成分转变。为了更好地支持我们的分析EMV处理过程中的化学成分变化，光学显微组织和差示扫描量热法（DSC）的配置文件补充从连续铸造Al-7重量% Si合金坯料。对Al-20wt%Sn和Al-7wt%Si合金的实验结果表明，只要在适当的条件下进行，电磁搅拌技术在改善凝固组织和力学性能方面是十分有效和实用的。
Homogenous distribution of the Sn phase in the Al–Sn alloy is beneficial for improved properties. However, the alloy has a metastable immiscibility gap that results in macrosegregation of phases in a usual casting. In the present study, the alloy with an actual composition of Al–20 wt% Sn–1 wt% Cu (referred to Al–20 wt% Sn hereafter for simplicity) was solidified in a static magnetic field when alternating current flowed through the alloy, from which electromagnetic vibration (EMV) was imposed upon the solidifying liquid. Solidified microstructures were observed and characterized in terms of the low-melting-point Sn phase. It was found that when EMV was imposed at the frequency off= 100 Hz, the Sn phase could be refined and dispersed homogenously in the primary Al matrix, which formed a contrast with the continuous Sn network in a usual casting solidified without EMV imposition. The specimen with fine Sn dispersions had an improved elongation in tensile tests. The solidification mechanism was discussed in terms of the structure formation and solute distribution when EMV was imposed during directional solidification. The uncoupled movement between the primary Al solid solution phase and the surrounding liquid may breakdown the Sn liquid film into discrete segments and thus form isolated particles at the final solidification stage. Meanwhile, this uncoupled movement can induce forced fluid flow that can stir the melt to homogenize the solute distribution in the remaining liquid pool. The composition transition was considered when EMV was imposed. To better support our analysis on the chemical composition variation during EMV processing, optical microstructures and differential scanning calorimetry (DSC) profiles were supplemented from a continuously cast Al–7 wt% Si alloy billet. The results of the Al–20 wt% Sn and Al–7 wt% Si alloys demonstrate that the EMV technique should be quite effective and applicable in improving solidification structures and mechanical properties provided that it is proceeded under appropriate conditions.