| Abstrakt: |
By means of particle tracking autoradiography (PTA), the diffusion coefficients of boron between 900 and 1200°C were measured in 04MnNbB steel, 25MnTiB steel, Ni-B, Fe-30%Ni-B and Fe-3%Si-B alloys, and the frequency factor D0and activation energy Qwere obtained respectively. The experiment results indicated that there was an obvious difference between the present result and the result obtained by Busby (in 1953). It was found that the boron diffusivity in γ-Fe increased as Ni was added. The diffusivity of boron in Fe-3%Si-B alloy with b.c.c. structure was much slower than one obtained by Busby in α-Fe (1954), which, however, was much faster than the results obtained in γ-Fe (with f.c.c. structure). Based on the present data of boron diffusion coefficients, the mechanism of segregation of boron to grain boundaries is discussed. |
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