Effects of adding 0.3 wt.% Al in Zn bath on the microstructure and reaction kinetics of intermetallic compounds have been studied using Co/Zn and Co/Zn-Al solid/liquid diffusion couples by means of scanning electron microscopy (SEM) and wave dispersive spectrometry (WDS). The intermetallic compounds in the Co-Zn interface have been identified and the diffusion process of Al in zinc bath has been analyzed. The diffusion constants of intermetallic compounds have been evaluated. The chemical potential of Al and standard Gibbs free energy of intermetallic compounds have been calculated using the Co content as a variable based on the calculation of phase diagram (CALPHAD) method. The results show that the chemical potential of Al decreases with increasing Co. At the solid/liquid interface, the Co content is high, the chemical potential of Al atoms is lower than that in other areas, uphill diffusion of Al atoms occurs, and an Al-rich metastable phase forms. The Gibbs free energy of the CoAl phase is lower than that of Co-Zn compounds; therefore, the Co atoms diffuse through the γ2 layer into the Al-rich area and nucleate to form a shape-stable CoAl layer at the solid/liquid interface and significantly inhibit the Co-Zn interfacial reaction.

中文翻译：

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锌浴中添加铝对Co-Zn界面反应的影响

通过扫描电子显微镜（SEM）和波色散研究了Co / Zn和Co / Zn-Al固/液扩散对，研究了在锌浴中添加0.3 wt。％的Al对金属间化合物的微观结构和反应动力学的影响。光谱仪（WDS）。鉴定了Co-Zn界面中的金属间化合物，并分析了Al在锌浴中的扩散过程。已经评估了金属间化合物的扩散常数。根据相图的计算（CALPHAD），使用Co含量作为变量，计算了Al的化学势和标准的金属间化合物的Gibbs自由能。结果表明，Al的化学势随Co的增加而降低。在固/液界面处，Co含量高，Al原子的化学势低于其他区域，发生Al原子的上坡扩散，并形成富含Al的亚稳相。CoAl相的吉布斯自由能低于Co-Zn化合物的吉布斯自由能。因此，Co原子通过γ2层扩散到Al富集区域并成核，在固/液界面处形成形状稳定的CoAl层，并显着抑制了Co-Zn界面反应。