Methods for alloy migration sintering

Abstract

Methods are provided for fabricating a sintered and solid element from an otherwise unsinterable material, utilizing the property of that material that it will form an eutectic composition or alloy with a suitable alloying agent at a temperature which is below the plastic deformation temperature of the material. Discrete particles of the material to be sintered--such as grains or wire pieces--are coated with a thin coating of the alloying agent and are packed into the position where they are to be sintered. Then, the coated grains or wire pieces are heated so that at least the coating and the regions of the grains just below the coating are slowly raised in temperature. Diffusion regions of the alloying agent into the grains of the sinterable material will then occur. Further heating continues so that at least the diffusion regions increase in temperature to just slightly above the eutectic melting point. Localized melting of the diffusion regions occurs where the eutectic concentration is reached, and adjacent grains therefore begin to share the localized melting regions and become mutually wet. The alloying agent then continues to diffuse, and drops in concentration, so that it freezes out of the localized melting regions. The melting point of the melting regions therefore tends to rise, and the wetted melted regions freeze to form a sintered and solid element.