Phase transformation, kinetics and thermodynamics during the combustion synthesis of Mg2Al3 alloy
Phase transformation, kinetics and thermodynamics during the combustion synthesis of Mg2Al3 alloy
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Mg2Al3合金燃烧合成过程中的相变、动力学和热力学
DOI：
10.1016/j.jallcom.2014.12.191
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发表时间：
2015-04
影响因子：
6.2
通讯作者：
Liquan Li
中科院分区：
文献类型：
--
作者：
Yuli Zhou;Yanglin Zhu;Yunfeng Zhu;Liquan Li
首次采用燃烧合成（CS）工艺制备了Mg2Al3合金。通过对两种途径获得的中间产物进行 X 射线衍射 (XRD) 分析，研究了该过程中的相变。一种是在CS反应器中在不同温度下合成的，另一种是在差示扫描量热计（DSC）测试期间在不同温度下淬火的。结果表明，单质Mg和Al在加热过程中形成Mg2Al3合金经历了四个阶段，同时伴随着Mg17Al12合金的出现和转变。在第一阶段（从室温到约 633 K），Mg17Al12 相先于 Mg2Al3 合金形核和生长，因为在此条件下 Al 的扩散率相对较高，而 Mg17Al12 合金的形成能较低。第二阶段（633~713 K）Mg17Al12与Mg发生共晶反应，形成液相，有效促进了合金化过程，从而导致Mg完全消失。在第三阶段（从713到723 K），除了Mg2Al3合金显着的吸热熔化之外，残余的Mg17Al12和Al之间发生了包晶反应。最终在723 K加热后立即获得高纯度的Mg2Al3单相。基于这些实验结果，从动力学和热力学角度提出并讨论了Mg2Al3合金的燃烧合成机理。
The Mg2Al3alloy was prepared by the combustion synthesis (CS) process for the first time. The phase transformation during the process was investigated by X-ray diffraction (XRD) analysis of the intermediate products obtained from two pathways. One was synthesized at different temperatures in the CS reactor, and the other was quenched at different temperatures during the differential scanning calorimeter (DSC) test. The results showed that the formation of Mg2Al3alloy from elemental Mg and Al experienced four stages upon heating, accompanied with the appearance and transformation of Mg17Al12alloy. In the first stage (from room temperature to about 633 K), the Mg17Al12phase nucleated and grew prior to the Mg2Al3alloy, owing to the relatively higher diffusivity of Al and lower formation energy of Mg17Al12alloy under this condition. The second stage (from 633 to 713 K) included a eutectic reaction between Mg17Al12and Mg to form the liquid phase which promoted the alloying process effectively, thus leading to the disappearance of Mg completely. In the third stage (from 713 to 723 K), the peritectoid reaction between residual Mg17Al12and Al occurred, besides the significant endothermic melting of Mg2Al3alloy. And finally Mg2Al3single phase with high purity was obtained immediately after heating upon 723 K. Based on these experimental results, the mechanism on the combustion synthesis of Mg2Al3alloy was proposed and discussed from both kinetic and thermodynamic perspectives.
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