The movement of atoms during twinning is described as a simple relative movement and not by means of a shear parallel to the twin plane, even with added "shuffles". It is shown that displacive waves similar to those which describe the p + w transformation, can be associated with these atom movements.Le mouvement des atomes au cours du maclage n'est pas dkcrit ici par un cisaillement parall6le au plan de macle associk kventuellement B des "shuffles", mais par un mouvement relatif simple des atomes. Les deplacements des atomes peuvent ktre associks a des ondes displacives analogues a celles decrivant la transformation pw. l) 15, Rue Georges Urbain, 94400 VitryISeine, France. 2, 11, Rue Pierre e t Marie Curie, 75231 Paris Cedex 05, France.

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Previously a model was proposed for {1012} and {1122} twinning in h.c.p. metals. Here a model is developed which describes {1011} and {1013} twinning and {1011} {1012} double twinning in an analogous way by a simple relative movement of atoms which is not a shear parallel to the twin plane, accompanied by complex shuffles.