Pore ​​structure Control And Three - Dimensional Characterization Of Lotus - Shaped Porous

Gas-Metal eutectic solidification is a new technology to fabricate lotus-type porous metal (also known as Gasar). The gas pores of the porous materials fabricated by Gasar process are cylindrical in shape, and grow along the solidification direction. Owing to this pore structure, lotus-type porous metal has more excellent properties than the traditional porous materials, such as mechanics, acoustics, thermal and electrical performance. The lotus-type porous metals have important potential application on many fields, such as large molecules in filter, self-lubricating bearings, catalyst carrier, heat exchanger, and so on.In this study, lotus-type porous Cu were successfully fabricated by using the mold casting device under different processing parameters. The influence of the technological parameters (the hydrogen pressure, argon gas pressure and melt temperature) on the porosity, pore size and distribution of the lotus-shape porous Cu was analyzed experimentally and theoretically.It is found that the hydrogen and argon pressure had a significant influence on porosity. Under high to medium pressure, porosity decreased with the increasing of the hydrogen pressure PH2when using pure hydrogen; Porosity decreased with the increasing of the argon partial pressure PAr when the PH2is constant. Under lower pressure, however, porosity increased with increasing PH2, when pure hydrogen was used as the atmosphere.The size and distribution of the pores also had close relations with the process parameters. For the lotus-type porous Cu obtained under pure hydrogen atmoshpere, in the high pressure range, the average diameter of the pores decreased and the uniformity of the distribution increased with the increasing of the hydrogen pressure. Within the lower pressure range, however, the average diameter of pores increased gradually and the uniformity of the distribution increased with the increasing of hydrogen pressure. When using the mixture gas of hydrogen and argon, and the value of PH2remains constant, the average diameter of the pores decreased and the uniformity of the distribution increased first and then decreased with the increasing of PAr.When the gas pressure and casting conditions remain constant, the pore diameter increased with the temperature increasing.The solidification solidification rate VS and bubbles rising rate VG were represented. And a range of porous structure formation was concluded. When VS≥VG, the lotus-type porous structure could be formed. The corresponding experiment results showed that the theoretical results were meaningful.A lotus-type porous Cu sample with typical gas pore structure was selected, and subjected to3D reconstruction. The sample was cut into slices by wire cutting machine first. Then the pictures of the sample slices were obtained, and the three-dimensional reconstruction software Mimics was used for the3D reconstruction. The growth of the pore space structure was observed and analyzed. It could be seen that the gas pore merger coarsening, new nucleation and interrupt phenomenon existed in the growth process of the pores. And the gas pore merger coarsening was the main phenomenon that occured, throughout the solidification process. At the same time, according to the porosity of the slices, the hole rate of the sample was analyzed. As a result, the hole rate of single slice had little difference, and the hole rate gradually reduced with the growth of the porosity, there was about1%of the value in reducing on each0.9mm height.