The Fe and Mo tracer diffusion in Fe91-yMo8Cu1By alloys was studied by using the serial-sectioning method at 548 to 773K. The measurements were performed using 3 alloys which differed in Fe/B ratio (y = 12, 15 and 17) and were prepared in the relaxed and crystalline states by using the planar flow-casting technique. Three modes of Fe diffusion were observed. The slowest one was volume diffusion in the relaxed amorphous phase. Faster diffusion occurred along the interfaces between crystallites and the relaxed amorphous phase. The fastest diffusion was observed along crystallite/crystallite grain boundaries. It was found that the rate of Mo volume diffusion, in the relaxed amorphous phase, was approximately the same as that of Fe; but Mo diffusion was much slower than Fe diffusion in grain boundaries. The activation enthalpy for Mo grain-boundary diffusion increased with increasing B concentration. The characteristics of short-circuit diffusion in structures where the relative fraction of relaxed-amorphous/crystallite type interfaces prevailed over crystallite/crystallite type ones depended sensitively upon the heat-treatment.

Diffusion and Structural Changes in Fe91-yMo8CuBy Alloys. J.Čermák, I.Stloukal: Journal of Physics - Condensed Matter, 2007, 19[15], 156219 (16pp)