ON REDISTRIBUTION OF Cr AND Si IN (Fe, Cr, Si)C NANOCOMPOSITES: MECHANOSYNTHESIS AND ANNEALING

The phase analysis of nanocrystalline alloys of composition (FeCrSi)C, where x = 0.05 and 0.10, in the states after mechanosynthesis (MS) and subsequent annealing is performed by methods of X-ray diffraction, Mössbauer spectroscopy, and magnetic measurements. MS yields ~46~58 vol. % of the X-ray amorphous phase (XAP), ~30~39 vol. % of χ-carbide, and only ~9~11 vol. % of cementite. Mechanosynthesized carbides are doped both with chromium and silicon. During annealing in the temperature range T = 400 - 500°C, the process of silicon release from carbides with its subsequent dissolution in ferrite is completed. XAP crystallization is two-stage. The first stage (T < 500°C) is characterized by carbides formed out of Si-depleted regions of XAP. At the second stage (T ≥ 500°C), the residual XAP decomposes to form ferrite and cementite with a higher concentration of Cr than that of the cementite formed both at the first stage of XAP crystallization and during MS. Further increase of T leads to a more homogeneous distribution of chromium atoms in cementite.