Temperature dependence of the lattice parameter and Debye-Waller factor of a high-chromium pressure-vessel steel

The method of thermal neutron diffraction has been used to study samples of the EK-181 steel at temperatures of 15 to 973 K in an IBR-2 reactor (Joint Institute for Nuclear Research (JINR)). Temperature dependences of the lattice parameter, internal textural stresses (of the third kind), and the Debye-Waller factor of this steel have been calculated from diffraction spectra by the Rietveld method. It has been found that at low temperatures the temperature dependence of the lattice parameter in the EK-181 steel (RUSFER EK-181) differs from the corresponding dependence in pure iron and binary iron-chromium alloys containing 12 and 16% Cr. Also, a broadening of the (200) reflection has been observed in the diffraction spectra of the EK-181 steel and the Fe-12Cr alloy, while it is not detected in the spectra of Fe-16Cr and pure iron.