Understanding centrifugal casting in the manufacture of functionally graded materials

Centrifugal casting is a shaping technique intended for ceramic tubular structure manufacture, where the particle size and density are exploited to produce asymmetrical membranes and functionally graded materials. However, some well-established insights about particle segregation are debatable and remain unclear. For instance, small particles do not necessarily stay in the inner region, and the bigger particles do not accumulate in the outer. Herein several manufacturing parameters were studied through Taguchi's robust design, using discrete element method-based simulations to generate the data. Alumina powder was used as model material and water as the liquid phase, to assess the green cast formation time, the cast thickness, the roundness, the changes in relative density, and particle size distribution along the cast's cross-section. The mean particle diameter and the rotation speed are the most influential parameters for the casting time. The volume fraction of solids on the precursor slurry is decisive regarding the cast structural properties, and particle segregation is negligible, except for size differences above one order of magnitude. When a fraction of denser nickel powder was added, density segregation was also observed, but the size differences can overshadow its effect. In addition, alumina and nickel particles were cast in a lab-scale centrifuge and experimentally validated the segregation of particles. The centrifugal casting method was successfully applied for producing the Al2O3-Ni composites with a gradient distribution of the Ni phase.

Schlagworte

Centrifugal casting

Discrete element method

Functionally graded materials

Hierarchically structured materials

Size segregation

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Understanding centrifugal casting in the manufacture of functionally graded materials