An 18Ni (300) maraging steel possessing lath martensite structure was deformed by four passes of equal-channel angular pressing at ambient temperature. Line profile analysis of X-ray diffraction patterns identified strong strain anisotropy and remarkable increases in the relative fraction of screw dislocations after equal-channel angular pressing. The strain anisotropy was reasonably accounted for by the anisotropy of elastic constants. Domination of screw dislocations in the deformed structure was attributed to the preferred annihilation of edge dislocations in the early stages of deformation along with the difficulties for annihilation of screw dislocations by cross slipping. Cobalt addition was mainly assumed to make cross slipping difficult by reducing stacking-fault energy and favoring short-range ordering.

X-ray Diffraction Study on the Strain Anisotropy and Dislocation Structure of Deformed Lath Martensite. S.H.Nedjad, F.H.Nasab, M.R.M.Garabagh, S.R.Damadi, M.N.Ahmadabadi: Metallurgical and Materials Transactions A, 2011, 42[8], 2493-7