Indian Journal of Engineering & Materials Sciences

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Effects of adding aluminium in zinc bath on Co-Zn interfacial reaction


Affiliations
1 Key Laboratory of Materials Design and Preparation Technology of Hunan Province, School of Materials Science and Engineering, Xiangtan University, Hunan 411105, PR, China
2 National-Provincial Laboratory of Special Function Thin Film Materials, School of Materials Science and Engineering, Xiangtan University, Hunan 411105, PR, China
3 Key Laboratory of Materials Design and Preparation Technology of Hunan Province, School of Materials Science and Engineering, Xiangtan University, Hunan 411105, PR
4 National-Provincial Laboratory of Special Function Thin Film Materials, School of Materials Science and Engineering, Xiangtan University, Hunan 411105, PR

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.
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  • Effects of adding aluminium in zinc bath on Co-Zn interfacial reaction

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Authors

Yongxiong Liu
Key Laboratory of Materials Design and Preparation Technology of Hunan Province, School of Materials Science and Engineering, Xiangtan University, Hunan 411105, PR, China
Yongxiong Liu
National-Provincial Laboratory of Special Function Thin Film Materials, School of Materials Science and Engineering, Xiangtan University, Hunan 411105, PR, China
Fucheng Yin
Key Laboratory of Materials Design and Preparation Technology of Hunan Province, School of Materials Science and Engineering, Xiangtan University, Hunan 411105, PR, China
Fucheng Yin
National-Provincial Laboratory of Special Function Thin Film Materials, School of Materials Science and Engineering, Xiangtan University, Hunan 411105, PR, China
Zhi Li
Key Laboratory of Materials Design and Preparation Technology of Hunan Province, School of Materials Science and Engineering, Xiangtan University, Hunan 411105, PR
Zhi Li
National-Provincial Laboratory of Special Function Thin Film Materials, School of Materials Science and Engineering, Xiangtan University, Hunan 411105, PR
Zhu Chen
Key Laboratory of Materials Design and Preparation Technology of Hunan Province, School of Materials Science and Engineering, Xiangtan University, Hunan 411105, PR, China
Zhu Chen
National-Provincial Laboratory of Special Function Thin Film Materials, School of Materials Science and Engineering, Xiangtan University, Hunan 411105, PR, China
Manxiu Zhao
Key Laboratory of Materials Design and Preparation Technology of Hunan Province, School of Materials Science and Engineering, Xiangtan University, Hunan 411105, PR, China
Manxiu Zhao
National-Provincial Laboratory of Special Function Thin Film Materials, School of Materials Science and Engineering, Xiangtan University, Hunan 411105, PR, China
Zhaohui Long
Key Laboratory of Materials Design and Preparation Technology of Hunan Province, School of Materials Science and Engineering, Xiangtan University, Hunan 411105, PR, China
Zhaohui Long
National-Provincial Laboratory of Special Function Thin Film Materials, School of Materials Science and Engineering, Xiangtan University, Hunan 411105, PR, China

Abstract


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.