An 18R martensite phase was observed in the body-centered cubic matrix of this 0.11wt%C alloy after cooling from high temperatures. The crystal structure of the martensite was deduced from selected area diffraction and high-resolution imaging results. The martensite had an orthorhombic lattice, and could be described as a (42)3 structure rather than a (51)3 structure. It was found that the crystallography could be accurately predicted with regard to orientation, habit plane, shape strain direction and magnitude of lattice invariant shear. The Burgers vectors of the anti-coherency dislocation and shape strain direction were confirmed by using the 2-beam technique, and computer image simulation. Crystallographic analyses suggested that the body-centered cubic/(42)3 interface might be energetically more favorable than the body-centered cubic/(51)3 interface.

W.B.Lee, F.R.Chen, C.M.Wang: Materials Science Forum, 1995, 189-190, 241-8