Zhang Y H, Xu Y Y, Ye C Y, Sheng C, Sun J, Wang G, Miao X C, Song C J, Zhai Q J
State Key Laboratory of Advanced Special Steels, Shanghai Key Laboratory of Advanced Ferrometallurgy, School of Materials Science and Engineering, Materials Genome Institute, Shanghai University, Shanghai, 200072, P.R. China.
Centre of Advanced Materials Processing and Manufacturing (AMPAM), The University of Queensland, St Lucia, QLD, 4072, Australia.
Sci Rep. 2018 Feb 19;8(1):3242. doi: 10.1038/s41598-018-21709-y.
Significant grain refinement in cast metals can be achieved through the application of electric currents during the solidification process. The present paper investigates the distribution of electric currents on the grain size of solidified Al-7wt.%Si alloy under the application of electric current with constant parameters flowing through two parallel electrodes into the melt within a cylindrical mould. The distribution of electric current was controlled by applying an electrical insulation material coating, boron nitride (NB), to the sidewall of the electrodes. Experimental results showed that the employment of these insulated electrodes can reduce grain size in comparison with the reference case of electrodes without BN coating. Flow measurements were performed in Ga-20wt.%In-12wt.%Sn liquid metal. Higher intensity forced flow occurred when the sidewall of the electrodes was insulated. In order to understand the underlying mechanism behind the stronger forced flow, corresponding numerical simulations were performed to reveal the distributions of the electric current, magnetic field, Lorentz force, and the resultant forced flow. The results achieved indicate that the mechanism of grain refinement driven by electric current is dendrite fragmentation induced by forced flow. In addition, a novel approach to enhance the grain refinement without additional input of current energy was developed.
通过在凝固过程中施加电流，可以实现铸造金属的显著晶粒细化。本文研究了在恒定参数电流通过两个平行电极流入圆柱形模具内的熔体时，凝固的Al-7wt.%Si合金晶粒尺寸上电流的分布情况。通过在电极侧壁施加电绝缘材料涂层氮化硼（NB）来控制电流分布。实验结果表明，与未涂覆BN的电极参考情况相比，使用这些绝缘电极可以减小晶粒尺寸。在Ga-20wt.%In-12wt.%Sn液态金属中进行了流动测量。当电极侧壁绝缘时，会出现更高强度的强制流动。为了理解更强强制流动背后的潜在机制，进行了相应的数值模拟，以揭示电流、磁场、洛伦兹力和由此产生的强制流动的分布。所取得的结果表明，电流驱动晶粒细化的机制是由强制流动引起的枝晶破碎。此外，还开发了一种无需额外输入电流能量即可增强晶粒细化的新方法。
