Jingkun Yu

Refinement of inclusions in molten steel by electric current pulse

Abstract The refinement of inclusions in molten steel induced by a continuous electric current pulse was investigated at 1823 K. The results revealed that due to the application of electric current, the melted sulphide inclusions in molten steel were refined. Analysed from the thermodynamic theory, the refinement mechanism was ascribed to the decrease in the system free energy that resulted from the formation of the refined sulphide inclusions in molten steel at 1823 K. Hence, the electric current pulse treatment may be a new method to refine inclusions in molten metallic materials in the future.

Improvement of pitting corrosion resistance of stainless steel by electric current pulse

ABSTRACT The electric current pulse (ECP) was applied on the liquidus of 304 stainless steel during solidification and the pitting corrosion of the water-quenched specimens was explored in the present work. The results revealed that the utilisation of ECP can inhibit manganese sulphide from segregating around oxide inclusions during solidification and consequently, the pitting corrosion resistance of ECPed steel was significantly improved. Hence, the application of ECP during solidification might be an efficient way to improve the pitting corrosion resistance of the 304 stainless steel. This paper is part of a themed issue on Materials in External Fields.

Effect of electric current pulse on preparation of nano Y2O3

ABSTRACT The effect of electric current pulse (ECP) on preparing nano Y2O3 powder was initially investigated in this paper. From the determination of thermogravimetric analysis, differential scanning calorimetry and X-ray diffraction, it was revealed that the composition of non-calcined precursor had changed due to the application of ECP. In addition, the scanning electron microscope results indicated that Y2O3 powders fabricated by ECP treatment had less aggregate and were in nano size. Therefore, the ECP treatment is a promising way to prepare nano Y2O3 powder. This paper is part of a themed issue on Materials in External Fields.

Effect of calcia additive on the grain growth of yttria

The effect of calcia on the grain growth of yttria was investigated in present work. The results shown that by adding calcia, yttria was sintered as low as 1300°C and abnormal grain growth model was observed over 1500°C. When higher than 1600°C, lots of closed pores were formed in the coarse yttria grains and the relative density was decreased with the increasing temperature and prolonging soaking time. Through theoretical analysis, it was known that oxygen vacancies were formed during the solid solution of Ca2+ into Y3+ and they were ascribed to the increasing of grain boundary diffusion of yttria. The developed yttria might be an applicable material for vacuum induction melting process to produce high purity titanium and its alloys.