The Analysis of Liquid–Metal Flow Effect on Solidification Microstructures

• Main Authors: Cheng-Han Tsai, 蔡政翰
• Other Authors: Long-Sun Chao
• Format: Others
• Language: zh-TW
• Published: 2005
• Online Access: http://ndltd.ncl.edu.tw/handle/37469416518602809774

碩士 === 國立成功大學 === 工程科學系碩博士班 === 93 === 　　A solidification process is a complicated problem and its control parameters are not easy to handle. Therefore, the defects in the materials during solidification are easily brought out and influence the quality of materials. However, the computer simulation of the solidification microstructures could help analyze their influences in velocity, temperature and concentration fields to enhance the material quality. A three-dimensional model of a cellular growth was built in our work by using the self-consistent cellular shape. The numerical method was the finite element method, in which the skyline storage mode and the LU decomposition method were used to solve the matrix equations. Gauss quadrature integration was adopted to compute the integration formulations and the penalty formulation method, which substituted for the pressure term in the momentum equations, was applied to fluid field to reduce the computational difficulty. From the simulated results, the feasibilities of these methods in velocity, temperature and concentration fields were proved by some tests of specific 2-D and 3-D models. For the 3-D simulation of the cellular growth, the effect of simple shear flow only imposed on the vicinity of the cell tip due to the block of the cell and therefore no obvious influence elsewhere below the vicinity of the tip was observed. For this reason, the temperature and concentration distributions mainly followed the growth direction of the cell. The latent heat release and solute diffusion increased the temperature and concentration respectively at the solidification interface. The fluid flow could bring the solute near the cell tip from the upstream to the downstream to make the latter one have the higher concentration. Contrarily, the fluid flow effect on the temperature field near the cell tip was not obvious.