A phase Doppler particle analyzer (PDPA), also referred to as phase Doppler interferometer (PDI), is used to serve the research needs of several ongoing research programs dealing with droplet-based processes of metals and composites at University of California, Davis. Spray forming (also referred to as spray atomization and deposition) is a state-of-the-art technology for manufacturing, droplet-based, advanced materials that exhibit superior mechanical properties. It provides a unique opportunity for achieving combinations of properties that are otherwise unachievable with equilibrium materials and near-net-shape control of products. The highly non-equilibrium thermal and solidification conditions that are present during spray forming may be commercially exploited to develop novel materials, such as ultra-high melting temperature and ultra-light-weight materials, that are difficult to process using conventional methods. PDPA instrumentation used will enhance in-depth understanding of fluid flow phenomena of metal sprays, in-situ, during spray forming, including spatial and temporal droplet size and distribution, droplet velocity and distribution, atomizing gas velocity, mass flow rate, and droplet number density. To that effect, the successful implementation and application of the instrument can further our understanding of the following critical issues in spray forming: thermal condition of materials during atomization, thermal condition of materials during deposition, solidification conditions during atomization, solidification conditions during deposition, formation mechanisms of equiaxed grains, grain refinement mechanisms during deposition, and control of porosity formation. In-depth understanding of such phenomena will accordingly, allow us to apply spray forming for the controlled production of materials with previously selected morphology, level of porosity, composition and microstructure. It also allows us to compare experimental observations by PDPA with predictions by modeling simulation in which models await for verification. PDPA instrumentation is being applied to evaluate the currently available nozzles for achieving optimum performance and for further enhancing nozzle design concepts.