Phase states of Fe–Mo–C spinning alloys at high temperatures

Abstract

Evolution of the phase composition of Fe-Mo-C spinning alloys is investigated in situ with hightemperature x-ray diffraction from room temperature to solidus. The temperature range over which the metastable β-Mn-like phase exists is determined. It is shown that the γ-Fe-based fcc-phase and Mo 2 C-based solid solution coexist in equilibrium at 1273 K and the γ-phase and η-carbointermetallide of W 3 Fe 3 C type coexist with the liquid phase at 1473 K. The vertical section at 11 at.% carbon is plotted.

Projection of the solidus surface of the Fe–Mo–C system in the composition range 0–40 at.% C

“…The difference between two cycles of heating and cooling successively recorded for the same sample in one experiment (for example, alloy 14) is that the first heating curve shows an endothermic effect, which begins at 645°C and has a peak at 710°C. As shown in [9], this effect corresponds to the decomposition of the metastable π phase (of β-Mn type) that forms during spinning.…”

Stability of the β-Mn structure in rapidly quenched Fe–Mo–Cr–C alloys at high temperatures

“…2) of the lattice parameters of the π and χ phases (confidence intervals of the lattice parameters of the phases are evaluated using the intensity ratio of the diffraction peaks and background) fits to a linear function, describing, in our opinion, only thermal expansion of the phases, ignoring diffusion exchange with other phases of the sample. The latter is confirmed by agreement (within the experimental error) between * RQ samples were obtained by V. V. Kuprin, Head of the Melting Division, using the unit developed at the Frantsevich Institute for Problems of Materials Science and the procedure described in [3] for flat casting on a rapidly rotating, internally cooled drum. ** ftp://ftp.bam.de/Powder_Cell/pcw23.exe.…”

“…To select composition for a Fe-Mo-Cr-C sample, we used data on Fe-Mo-C alloys reported in [3], where the formation of manganese-like phases has been reliably established. We took account of the following conditions needed for α-and β-Mn structures to emerge according to [5,6]: the number of valence electrons of an average metal per atom in the formula of a compound tends to seven and the radius ratio of metallic components is about 1 Frantsevich Institute for Problems of Materials Science, National Academy of Sciences of Ukraine, Kiev, Ukraine.…”

“…1.1. These conditions were met by composition 51.9Fe11.1Mo26.3Cr10.7C (at.%) resulting from partial substitution of iron by chromium in 78.4Fe10.8Mo10.8C (at.%) spinning alloy, in which the weight content of the π phase was about 90% as stated in [3].…”

“…To continue experimental and theoretical studies focusing on the formation of manganese-like phases in iron-based alloys, such as Fe-Mo [1, 2] binary and Fe-Mo-C [3] and Fe-Mo-Cr [4] ternary systems, we have analyzed the evolution of phase transformations involving Mn-like phases in the Fe-Mo-Cr-C quaternary system using high-temperature x-ray diffraction in the range from room to liquidus temperatures.…”