A Hollow Cylinder of Functionally Gradient Materials Fabricated by Centrifugal Molding Technique

摘要

Hollow cyclinders of functionally graded materials (FGMs) composed of low-density alumina and high-density tungsten powders with two kinds of particle size were fabricated using a centrifugal molding technique. Fine and coarse particle sizes of tungsten powders were used to make continuous and gradual variations of their composition. The alumina and tungsten powders were mixed wiht ethanol solvent, dispersant, and binder, and rotated at 3000 rpm in a steep mold of the centrifugal molding equipment. Afer casting and drying the slurry, the FGM cake was sintered in reduced atmosphere of H_2/N_2 environment at 1600 deg C for 3 h. Continuously gradient constituents across the thickness of the hollow cylinder were obtained with the range of the slurry viscosity from 100 mPa centre dot s to 300 mPa centre dot s by adjusting the mixture ratio of the two particle sizes of tungsten powders. Residual thermal stresses generated during the cooling procvess were also analyzed numerically for each fabricated FGM cylinder with different variation of microstructure using a multi-layered technique. The analytical results showed that tensile hoop stressees appeared on the inner surface of the hollow cylinder and compressive stresses on the outer surface, and these residual stresses were released by selecting appropriate gradients with good dispersion of particles.