Abstract: A TEM investigation was made on the morphology,orientation relationship and habit plane of three alloy nitrides,namely CrN,VN and Mo_2N simultaneously formed within the diffussional nitrided layers in an H13 steel nitrided at 580℃.It was.found that the nitrides were precipitated by continuous clustering and subsequent ordering of both interstitial(N)and substitutional(Cr,V,Mo)solutes on {001} habit plane,and that the observed morphology and crystallography of the nitrides were in good agreement with the predictions from the invariant line stain model proposed for precipitation transformations.

Key words: alloy nitride, mixed cluster, habit plane, invariant line strain