Coarsening Kinetics of γ' Precipitates in Dendritic Regions of a Ni3 Al Base Alloy

Coarsening behavior of γ’ precipitates in the dendritic regions of a Ni 3 Al base alloy containing chromium,molybdenum,zirconium and boron was investigated.Annealing treatment was performed up to 50 h at 900,1000 and 1100℃.The alloy was produced by vacuum-arc remelting technique.Results show that coarsening of the γ’ precipitates in this complex alloy containing high volume fractions of γ’ phase follows Lifshitz-Slyozov-Wagner(LSW) theory.Coarsening activation energy of the γ’ precipitates was evaluated to be about 253.5 kJ.mol-1 which shows that the growth phenomenon is controlled by volume diffusion of aluminum.With an innovative approach,diffusion coefficient of the solute element(s) and the interfacial energy between γ’ precipitates and γ’(matrix) were estimated at 900,1000 and 1100℃.Accordingly,the interfacial energies at 900,1000 and 1100℃ are 4.49±1.48,2.08±0.69 and 0.98±0.32 mJ.m-2,respectively.Also the diffusivities of solute element(s) at these temperatures are 3.41±1.08,30±9.5 and 145.15±45.85(10-15 m-2.s-1),respectively.