FestphasenSintern

FestphasenSintern, or solid-phase sintering, is a powder processing method in which a compact of fine particles is heated to a temperature below the melting point of its constituents. In the solid state, atoms diffuse within grains and along grain boundaries, enabling neck growth between particles and gradual densification without melting the material.

During solid-phase sintering, the early stage features the formation of interparticle necks and a reorganization of porosity. Densification is driven mainly by diffusion through the solid lattice and along grain boundaries, with surface diffusion contributing to neck formation but not to net shrinkage. In the later stages, grain growth can occur as porosity becomes more isolated, and overall density increases while the microstructure coarsens. The process is strongly affected by powder characteristics (particle size distribution, impurities, shape), green density, and any applied constraint or pressure.

Process parameters commonly include peak temperature (below the melting point), heating and cooling rates, dwell time, and atmosphere. External pressure can be applied through techniques such as hot pressing or hot isostatic pressing to enhance densification. Additives, lubricants, and dopants may be used to influence diffusion paths and grain growth. Some materials are prone to residual porosity or excessive grain growth if those conditions are not carefully controlled.

Applications and materials: FestphasenSintern is widely used for ceramics and some metallic powders in powder metallurgy, particularly when a liquid phase must be avoided to preserve purity or anisotropy. It enables components with controlled microstructures and dimensional stability, though it can require fine powders and precise processing to balance densification with grain growth.

See also: liquid-phase sintering, hot pressing, diffusion in solids.