Theoretical and experimental studies are conducted on metal alloy microstructural evolution during rapid thermal cycling. Particle dissolution, grain growth, liquid film formation, and subsequent solidification of intergranular liquid are considered. A physical model of the process is being developed, computer simulation employed, and experimental verification pursued. Analytical transmission electron microscopy is the primary microanalytical technique. The completed research should produce a computational model of microstructural evolution during a complete thermal cycle typical of a weld heat-affected zone. %%% Many multiphase alloys are subjected to rapid thermal processing, such as welding and surface modification through high energy beam melting or thermal spraying. This research will provide a verified computational model applicable to these processes.