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Wanning Z.,Shenyang Government Investment Project Evaluation Center | Dan S.,Shenyang University of Technology | Hongbing Z.,Shenyang University of Technology | Deyuan L.,Shenyang University of Technology | And 2 more authors.
China Foundry | Year: 2010

An investigation was made on the evolution of microstructures of hypoeutectic white cast iron slurry containing 2.5wt.%C and 1.8wt.%Si produced by rheocasting in which the solidifying alloy was vigorously agitated by electromagnetic stirrer during isothermal cooling processes, The results indicated that under the proper agitating temperatures and speeds applied, the dendrite structures in white cast iron slurry were gradually evolved into spherical structures during a certain agitating time. It also revealed that the bent dendrites were formed by either convection force or by the growth of the dendrites themselves in the bending direction; then, as they were in solidifying, they were gradually being alternated into separated particles and into more spherical structures at the end of the isothermal cooling process. Especially, the dendrites were granulated as the bending process proceeding, which suggested that they were caused by unwanted elements such as sulfur and phosphor usually contained in engineering cast iron. Convective flow of the melt caused corrosion on the dendritic segments where they were weaker in strength and lower in melting temperature because of higher concentration of sulfur or phosphor. And the granulation process for such dendrites formed in the melt became possible under the condition. Certainly, dendrite fragments are another factors considerable to function for spherical particles formation. A new mechanism, regarding to the rheocast structure formation of white cast iron, was suggested based on the structural evolution observed in the study.

Song D.,Shenyang University of Technology | Zhang W.-N.,Shenyang Government Investment Project Evaluation Center | Zhang H.-B.,Shenyang University of Technology | Li D.-Y.,Shenyang University of Technology | And 2 more authors.
Zhuzao/Foundry | Year: 2010

Iron-based composites containing 30vol.% in-situ synthesis ZrC particles were fabricated by using arc melting method. The microstructure, phase constituents and micro-hardness were checked by employing optical microscope(OM), X-ray diffraction(XRD) and micro-hardness tester. The results show that ZrC particles, as the only reinforcement, can form and distribute in fcc iron matrix. The cooling rate can affect both ZrC volume fraction and size. Therefore the lager the cooling rate is, the smaller the size of the ZrC particles becomes. It was also found that the micro-hardness of the composite increase with increasing the cooling rate.

Yutuo Z.,Shenyang Ligong University | Wanning Z.,Shenyang Government Investment Project Evaluation Center | Tie W.,Shenyang Ligong University | Liyan F.,Dalian Jinzhou Cable Co. | Chengzhi W.,Shenyang Ligong University
China Foundry | Year: 2011

Dendritic coarsening in Al-2mol%Si alloy during isothermal solidification at 880K was investigated by phase field modeling. Three coarsening mechanisms operate in the alloy: (a) melting of small dendrite arms; (b) coalescence of dendrites near the tips leading to the entrapment of liquid droplets; (c) smoothing of dendrites. Dendrite melting is found to be dominant in the stage of dendritic growth, whereas coalescence of dendrites and smoothing of dendrites are dominant during isothermal holding. The simulated results provide a better understanding of dendrite coarsening during isothermal solidification.

Yutuo Z.,Shenyang Ligong University | Guimao L.,Northeastern University China | Wanning Z.,Shenyang Government Investment Project Evaluation Center | Chengzhi W.,Shenyang Ligong University
China Foundry | Year: 2010

The new filling system is smooth filling without gas gap. It works well in avoiding the generation of defects such as porosity and inclusion. The pouring basin, sprue, runner and the gate of the bolster casting were designed according to the principle of the new filling system. The filling and solidification process of the bolster casting were also simulated. It was found that the filling process was smooth, and air entrapment and shrinkage were avoided. Finally, a further validation of the new filling system of bolster casting was carried out in a foundry.

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