Transmission Electron Microscopy studies of the structure of martensitic interfaces in Cu-Zn: Diffraction contrast
A Cu-38.6%Zn alloy was treated at 870°C and quenched in ice brine(10% NaOH) to produce martensitic transformation. The parent phase is bcc structure and the martensite phase is 9R close-packed structure. The orientation relationship of the parent phase and martensite was determined by the Kikuchi pattern and diffraction pattern. The experimental lattice deformation matrix can then be deduced from the orientation relationship and assumed correspondence. The lattice deformation matrices determined from experiment and calculated from CRAB martensite crystallography theory are as follows:As shown in Figure 1, a set of dislocations is observed in the martensitic interface whose Burgers vector is determined to be l/3[101]b by the two beam technique. The direction and the average spacing of these dislocations determined from experiment are [.49 . .47]b and 5±1nm respectively. This set of dislocations is consistent with the lattice invariant shear l/3[101]b on the ( 01)b plane with the magnitude 0.022 used in the CRAB martensite crystallography which corresponds to an anticoherency dislocation array with the spacing of 7.75nm and in the direction [.514,. ,.514]b. The habit plane determined from experiment is (.13,.65,.75 )b and close to (.13,.68,.72)b from the prediction of CRAB martensite crystallography.