The migration of Ni in martensites containing up to 30wt%Ni was studied at 300 to 700C by using electron microprobe techniques. Homogeneous austenite samples were quenched so as to obtain martensite. The diffusion coefficients were found by comparing the measured concentration profiles with the results of simulations. At temperatures greater than 410C, the diffusivities could be described by:

D (cm2/s) = 4.25 x 10-3 exp[-49.0(kcal/mol)/RT]

At below 410C, the diffusivity was described by:

D (cm2/s) = 2.27 x 10-15 exp[-10.6(kcal/mol)/RT]

The discontinuous nature of the Ni diffusion in these martensites was attributed to the high dislocation density. Thus, at temperatures greater than 410C, lattice diffusion was deduced to be the predominant mechanism.

A.D.Romig, J.I.Goldstein: Metallurgical Transactions A, 1981, 12[2], 243-9