DIFFUSION OF CU, FE AND SI IN L12-TYPE INTERMETALLIC COMPOUND NI3AL

Diffusion of Cu, Fe, and Si in the Ni3Al phase (gamma') of an intermetallic compound with L1(2) structure has been studied at temperatures from 1173 to 1598 K using the diffusion couples of (Ni-24.2 mol%Al/Ni-24.1 mol%/Al-4.73 mol%Cu), (Ni-24.2 mol%Al/Ni-23.7 mol%/Al-3.52 mol%Fe), and (Ni-24.2 mol%Al/Ni-22.3 mol%Al-3.14 mol%Si). The diffusion profiles in the annealed diffusion couples were measured by an electron probe microanalyzer. The diffusion coefficients of Cu, Fe, and Si in gamma of 24.2 mol% Al were evaluated from the diffusion profiles by Hall's method. The temperature dependence of the diffusion coefficients (m2/s) is presented as follows: D(Cu)(0) = 5.5 x 10(-3) exp (-323(kJ/mol)/RT) D(Fe)(0) = 2.7 x 10(-2) exp (-347(kJ/mol)/RT) D(Si)(0) = 4.8 x 10(-1) exp (-390(kJ/mol)/RT) The activation energies are found to be closely related to the substitution behavior of Cu, Fe and Si atoms in the L1(2) lattice sites of gamma'.