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Microstructure of as‐quenched 3.5 NiCrMoV rotor steel — Part II. Double diffraction
Author(s) -
Gates J. D.,
Atrens A.,
Smith I. O.
Publication year - 1987
Publication title -
materialwissenschaft und werkstofftechnik
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.285
H-Index - 38
eISSN - 1521-4052
pISSN - 0933-5137
DOI - 10.1002/mawe.19870180607
Subject(s) - diffraction , cementite , austenite , electron diffraction , martensite , materials science , crystallography , neutron diffraction , microstructure , metallurgy , optics , chemistry , physics
In a study of the microstructural features of 3.5 NiCrMoV steam turbine rotor steel in the as‐quenched state, correct interpretation of selected area electron diffraction patterns has been found to be nontrivial. A major complicating factor is the widespread occurrence of double diffraction associated with micro‐twins in the martensite. The resulting diffraction patterns are similar to those expected from cementite and may even suggest an orientation relationship consistent with the Bagaryatskii relationship. Moreover in the as‐quenched steel they are the only well‐developed diffraction patterns observed. Cases of failure to recognise double diffraction, with misinterpretation as evidence for the presence of cementite, have been brought to light. Double diffraction also occurs in regions containing retained austenite. A notation of the form d‐d hkl αis proposed for diffraction spots due to double diffraction micro‐twins, based on the observed relationship between the reciprocal lattice spacings of the double diffraction spots and those of the matrix spots.