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Having larger atomic size than that of Fe, rare earth (RE) atoms could not diffuse into the crystal lattice of Fe based on common opinion. However, it was proved that RE atoms could diffuse not only along grain boundary but also into grain internal. The mechanism of RE permeating into surface layers of steels and activation and catalysis effects of RE on thermo-chemical treatment process were studied. RE atom has considerable attraction for the iron atoms on the surface and diffuses inside by the vacancy mechanism. The activation and catalysis of RE in the thermo-chemical treatment process originally arise from the special electron-layer structure of RE, the low electronegativity of RE and the strong affinity of RE with many non-metal elements.
Having larger atomic size than that of Fe, rare earth (RE) atoms could not diffuse into the crystal lattice of Fe based on common opinion. However, it was proved that RE could not diffuse not only along grain boundary but also into grain internal. The mechanism of RE permeating into surface layers of steels and activation and catalysis effects of RE on thermo-chemical treatment processes were studied. RE atom has considerable attraction for the iron atoms on the surface and diffuses inside by the vacancy mechanism. The activation and catalysis of RE in the thermo-chemical treatment process originally arise from the special electron-layer structure of RE, the low electronegativity of RE and the strong affinity of RE with many non-metal elements.