Dilute alloys which contained up to 0.6wt%Nb were prepared. Diffusion couples between these alloys, and pure Fe, were prepared by spot-welding. After vacuum annealing, the diffusion profiles were determined by using electron probe microanalysis. The diffusion parameters were determined at one standard deviation by using the Grube method. In austenite, the interdiffusion of Nb was in good agreement with previous tracer diffusion data. At between 1147 and 1347C, the Nb diffusivity in an 0.58%Nb alloy could be described by:

D (mm2/s) = 6.17 x 102 exp[-293000)/RT]

Attempts to measure the diffusivity of Nb in ferrite were unsuccessful, due to the presence of an intermetallic phase and due to the fact that the solubility limit was exceeded. On the other hand, the solubility of Nb in ferrite was less than 0.24wt%.

Q.A.Shaikh: Materials Science and Technology, 1990, 6[12], 1177-80

Table 128

Diffusivity of 99Mo in Fe76Mo8CuB15