Communications: Discussion of 'Lattice Orientation Relationship between the M_2C Carbide and the Ferrite Matrix in the M50NiL Bearing Steel'

摘要

The orientation relationship reported in this article~[1] is not "new". Within the accuracy of orientation relationship determinations from electron diffraction spot patterns (typical error +- 2 deg),~[2] it is essentially the same as the orientation relationship between M_2C (C) and ferrite (alpha) reported nearly 20 years ago by Wang Rong and Dunlop,~[3] namely, (012)_(alpha)//(0001)_C [100]_(alpha)//[21-bar 1-bar 0]_C The Rong/Dunlop orientation relationship~[3] is related to the Pitsch/Schrader~[4] orientation relationship for M_2C in ferrite found by other workers~[5,6,7] by a rotation of 18.4 deg about the common parallel directions [100]_(alpha)//[21-bar 1-bar 0]_C.~[3,8] The orientation relationship determined by Song et al.~[1] is related to the Pitsch/Schrader orientation relationship~[4] by a rotation of 16.3 deg about the common parallel directions [100]_(alpha)//[21-bar 1-bar 0]_C. In other words, (012)_(alpha) is 2.1 deg from (000l)_C, not exactly parallel to (000l)_C, as in the Rong/Dunlop~[3] orientation relationship. This very small difference between the two orientation relationships is almost impossible to distinguish with electron diffraction spot patterns, and requires a more accurate technique such as convergent beam Kikuchi line patterns or the orientation of Moire fringes in the M_2C(ferrite interface.~[7]