Aging precipitation kinetics of Mg-Sc alloy with bcc+hcp two-phase
Aging precipitation kinetics of Mg-Sc alloy with bcc+hcp two-phase
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DOI：
10.1016/j.jallcom.2018.03.064
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发表时间：
2018-05
影响因子：
6.2
通讯作者：
Yukiko Ogawa;Y. Sutou;D. Ando;J. Koike
中科院分区：
文献类型：
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作者：
Yukiko Ogawa;Y. Sutou;D. Ando;J. Koike
在我们以前的研究中，我们报道了具有bcc（β）相的Mg-Sc合金通过在β相中形成细小的hcp（α）沉淀物而显示出显著的时效硬化。研究了α+β两相Mg-Sc合金的时效析出动力学。随着时效温度的升高，时效硬化孕育期缩短。用Austin-Rickett方程比Johnson-Mehl-Avrami-Kolmogorov方程更好地描述α相体积分数与时效时间的关系，得到的n值为1.2-1.4。根据α析出相的形态和α析出相的尺寸，提出了α+β两相Mg-Sc合金中α析出的机制是扩散控制反应，即α析出相以恒定或递减的形核速率一维长大。此外，α沉淀的活化能计算为83.5 kJ mol−1。该值远小于Mg中的自扩散，而与Mg中的晶界扩散，即界面扩散的值几乎相同。这表明α相的生长主要是沿α相和β相之间的界面沿着扩散。
In our previous research, we reported that Mg-Sc alloys with a bcc (β) phase showed significant age hardening by the formation of fine hcp (α) precipitates in the β phase. In this study, we investigated the kinetics of the aging precipitation in the α+β two-phase Mg-Sc alloy. The incubation time for age hardening became shorter with increasing aging temperature. The relationship between the volume fraction of α precipitates and aging time was better described by the Austin-Rickett equation than by the Johnson-Mehl-Avrami-Kolmogorov equation, and the obtainednvalues are 1.2–1.4. According to thenvalues and the morphology of fine α precipitates, the mechanism of α precipitation in the Mg-Sc alloy with an α+β two-phase was proposed to be a diffusion-controlled reaction, including the one-dimensional growth of α precipitates at a constant or decreasing nucleation rate. In addition, the activation energy for α precipitation was calculated to be 83.5 kJ mol−1. This value is much smaller than that of self-diffusion in Mg, while it is almost the same as that of grain boundary diffusion in Mg, namely interface diffusion. This reveals that the growth of α precipitates is dominated by interface diffusion along the boundaries between the α precipitate and the β phase.