This article reviews the fundamental solidification concepts for understanding microstructural evolution in fusion welds. The common concepts, namely, nucleation, competitive grain growth, constitutional supercooling, solute redistribution, and rapid solidification, depend on the solidification parameters during welding, are discussed. The article discusses important solidification parameters, including temperature gradient, solid/liquid interface growth rate, and cooling rate.
Dissimilar metal welding applications require careful control over the welding parameters and corresponding dilution level in order to produce welds with proper microstructure and properties for the intended service. This article reviews the relation between the dilution and bulk fusion-zone compositions and describes the effect of fusion welding parameters on dilution. It also provides typical examples of the microstructure and property control in dissimilar weld applications.