This is the wellknown K-S orientation relationship between bcc and fcc crystals.[1,7] This relationship shows that the close packed planes of ferrite are parallel to the closest packed planes of M23C6 carbide, and the closest packed direction of ferrite is parallel to that of M23C6 carbide. The planar spacing of (110) planes of the ferrite is d110 = 0.177 nm, and that of (111) planes of the M23C6 carbide is d111 = 0.600 nm.