Resolidification

Resolidification is the process by which a material that has been melted cools and returns to a solid state. In metallurgy and materials science, the term often refers to the solidification of a liquid metal or alloy after it has been melted by an external heat source, or to the re-solidification of a region that has been locally melted within a previously solid body. The process begins when the liquid temperature falls below its solidus or liquidus temperature, allowing nucleation and growth of solid crystals at the advancing solid–liquid interface. Nucleation can be homogeneous or heterogeneous, with impurities, grain boundaries, and second-phase particles acting as favored sites.

Microstructure is strongly affected by cooling rate, alloy composition, and the presence of pre-existing solid. Slow cooling generally yields larger grains and solute redistribution that can create segregation bands; rapid cooling promotes finer grains and, in some alloys, non-equilibrium compositions or amorphous structures. In many manufacturing contexts, resolidification occurs after processes that locally melt material, such as welding, soldering, casting, laser remelting, or additive manufacturing. The resolidified layer governs properties such as strength, toughness, hardness, residual stresses, and susceptibility to cracking or porosity.

Control of resolidification is achieved through process parameters (heat input, cooling rate, and dwell time), alloy design (grain refiners, solute additions, and intermetallics), and post-processing treatments. Understanding resolidification microstructure is essential for predicting performance in service and for optimizing manufacturing outcomes.