The coarsening process of solid grains in liquid matrix has been studied by the observation of the precipitation patterns around large W grains after liquid phase annealing of 88W-7Ni-5Cu alloy. The specimens were annealed at 1470℃ from 0.5 h to 16 h. Some specimens were annealed at 1470℃ for 0.5h were reannealed at the same temperature for various times. If the total annealing time was same as those of annealed specimens, the average grain size and linear intercept distribution of reannealed specimens were identical those of annealed specimens. And the two results agreed with Ardell's theoretical prediction. In the reannealed specimens, however, ring-shaped boundary in large grains was revealed after etching in Murakami solution. The formation of this etch-boundary was attributed to the chemical composition difference between the original grains and the precipitated layer formed on large grains during cooling. The etch boundary exhibited, therefore, the shape of the growing grain before and after the reannealing. Isolated large grains has grown radially from the etch-boundary if the neighbor grains are not very close to the isolated grains. When two large particles of equal size are in contact, solute atoms has precipitated around the two grains and the dihedral angle has been maintained. When two grains of different size are in contact the dihedral angle has been also maintained. Microstructural evidences showed clearly that the grain coarsening in W-Ni-Cu alloy during liquid phase annealing occurred by the solution-reprecipitation process of Ostwald ripening.
