Abstract
The study of deformation twinning has long history. However new, sometimes surprising, findings have shown that the phenomenon of deformation twinning still is not completely understood. During recent years, some debates are taking place in the scientific literature concerning deformation twinning mechanisms in metals with hcp structure. These debates deal with the importance of special twin boundary dislocations named disconnections, growth and nucleation of twins, non-Schmid behavior of twinning, difference of deformation produced by twins from simple shear. They invoked new propositions for atomistic mechanisms of deformation twinning. The purpose of this review is to compare the classical theories of interfacial defects with the new findings and prove that many of these findings can be understood in terms of these well-established theories. The main attention is paid to summarizing the explanations of different phenomena in terms of disconnection mechanisms in order to show that there is no contradiction between these mechanisms and the new findings.
Highlights
Mechanical twinning is an important mechanism of plastic deformation in metals with hexagonal crystal structure [1,2,3,4,5,6,7], e.g., magnesium or titanium alloys
Apart for the difference of Burgers vectors just described and the fact that grain boundary dislocations are confined to the grain boundary, bulk and grain boundary dislocations have the same characteristics, such as conservation of Burgers vectors, Frank rule for the energy balance of a dislocation reaction, etc
The process was observed during growth of twin coherent {1012} twin boundary by rearrangement of disconnections was directly observed in embryo, which was initially bounded by basal-prismatic interfaces
Summary
Mechanical (deformation) twinning is an important mechanism of plastic deformation in metals with hexagonal crystal structure [1,2,3,4,5,6,7], e.g., magnesium or titanium alloys. The characteristics of a deformation twin lead to the following constraints [3]: if the twin and matrix are to remain in contact, the deformation must be an invariant plane strain. A mode of deformation the plane of shear, and it contains η1 and intersects K2 , in the direction η2. This non-standard shape stimulated the development of new theories and theories and many debates concerning atomistic mechanisms of deformation twinning are present many debates concerning atomistic mechanisms of deformation twinning are present in recent in recent literature These debates deal with the importance of special twin boundary dislocations literature. The last section focuses on the 1012 deformation twinning describing the concepts that, together with the plane invariance, have generated much debate such as zero shear and Non-Schmid behavior
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