The program investigates the mechanisms of coarsening of precipitates in binary metal alloys. Existing theories predict that precipitate coarsening behavior is influenced by the volume fraction of precipitate. This effect should be maximized at low volume fractions. In this research pre-aging treatments are employed to produce a uniform composition in the metal matrix. This treatment is followed by an elevated temperature aging treatment to control the kinetics of precipitate growth and the particle size distributions. Metal alloy specimens are examined by transmission electron microscopy and magnetic techniques to measure precipitate volume fraction and growth rate. Related theoretical considerations take into account effects of coherency strains on the coarsening process. The metal alloys under investigation are binaries of nickel with additions of aluminum, silicon or titanium.
