TRANSMISSION ELECTRON-MICROSCOPY STUDY OF PLASTIC-DEFORMATION IN NIZR2

Plastic deformation mechanisms in the body centred tetragonal (C16-str ucture) NiZr2 compound have been studied using transmission electron m icroscopy. Dislocations, stacking faults and microtwins have been char acterized. Four families of dislocations have been identified: screw-t ype (b = [001]), edge-type ([001](110) and [100](1 (1) over bar 0) sys tems) and mixed-type (1/2[1 (1) over bar 1](110) system). Partial dilo cations associated with stacking faults have also been detected and an alysed. The plane of the faults is shown to be (1 (1) over bar 0) and the fault vectors 1/4 [111] and 1/4[11 (1) over bar]. A hard-sphere mo del illustrating the formation mechan ism of these stacking faults is proposed. The microtwins are found to be 60 degrees rotation twins aro und the [1 (1) over bar 0] direction and can be described by the stac king faults scheme.