Pressureless Sintering Of Powder Processed Functionally Graded Metal-Ceramic Plates

Abstract

The need exists to fabricate graded metal-ceramic composite armor specimens consisting of nickel and alumina through powder processing techniques and pressureless sintering for dynamic mechanical characterization. An approach is employed to control the thermal shrinkage of each microstructure during sintering by varying particle sizes of the two powders. Models were developed to understand both the nature of the porosity during sintering and the shrinkage behaviors of the composites. The relationship between porosity and sintered properties was characterized through microhardness measurements, indicating the reinforcing particles are debonded from the matrix and can be treated as additional porosity. The type of microstructure to be used in property models was characterized through optical microscopy. Porosity effects were incorporated into constitutive equations for a recently developed finite element sintering model, which was validated through comparison of predicted and experimental shape profiles of graded specimens and through correlation of stress profiles to fracture locations.