Peierls barriers of a-type edge and screw dislocations moving on basal and prismatic planes in magnesium

Exact shape of Peierls barriers are calculated for ⟨ a⟩ edge and screw dislocation gliding on basal and prismatic planes in magnesium by using of several popular interatomic potentials. Comparison of these potentials is performed in order to describe their abilities and limitations. Stability of different types of dislocation cores are analyzed as well as their mutual transformations during dislocation slip. It was found that the Peierls stresses and barrier height are dependent on core type. It was concluded that transformations of dislocation cores along minimal energy paths have to be taken into account for development of analytical models of the slip in magnesium. The results are compared with available first-principles calculations

Evolution of Matrix-Twin Interfaces of (101̅2) Twin in Magnesium

Recently, the presence of basal-prismatic interfaces in hexagonal close packed metals became subject of intensive investigation. We model the {101̅2} twin in magnesium bounded by two types of boundaries, i.e. {101̅2} interface and basal-prismatic facets. The migration of all boundary types is mediated by the motion of interfacial disconnections. It was shown that basal-prismatic interfaces play an important role in twin growth. The lengths of basal-prismatic facets remain constant during migration independently of the applied strain. In contrast, the {101̅2} interfaces increase their lengths during growth

Some aspects of double twinning in hexagonal metals

When plastic deformation cannot be carried by dislocations, mechanical twinning is often activated. This situation often takes place in hexagonal materials. In addition to general grain boundaries, twin boundaries as special interfaces play an important role not only for mechanical properties but for other properties of materials as well. This short paper is focused only on some processes related to double twinning and the conditions of its occurrence are considered. Geometrical aspects are analyzed for development mechanisms of different twin interfaces in connection to double twinning.Якщо пластична деформація не може здійснюватись шляхом дислокаційного ковзання, часто активується механічне двійникування. Ця ситуація часто виникає в гексагональних матеріалах. Поряд із звичайними границями зерен, двійникові границі, як спеціальні границі розділу, відіграють важливу роль у формуванні не тільки механічних, але й інших властивостей матеріалів. У цьому короткому повідомленні увага зосереджена лише на деяких процесах, пов'язаних з вторинним двійникуванням та умовами його виникнення. Аналізуються геометричні аспекти механізмів формування різних двійникових границь розділу у контексті вторинного двійникування.В случае, если пластическая деформация не может осуществляться путем дислокационного скольжения, часто активируется механическое двойникование. Эта ситуация часто возникает в гексагональных материалах. Наряду с обычными границами зерен, двойниковые границы, как специальные границы раздела, играют важную роль в формировании не только механических, но и других свойств материалов. В этом коротком сообщении внимание сосредоточено лишь на некоторых процессах, связанных с вторичным двойникованием и условиями его возникновения. Анализируются геометрические аспекты механизмов формирования различных двойниковых границ раздела в контексте вторичного двойникования

Topological Model of Austenite-Martensite Interfaces in Cu-Al-Ni Alloy

Discussion of the austenite-single-variant martensite interfaces in Cu-Al-Ni alloy is performed in the frame of a topological model of martensite interfaces. This model takes into account admissible defects lying in the interface. The results are compared with the experimental data obtained on the foils of Cu-Al-Ni alloys deformed in situ in a transmission electron microscope

Cu-Al-Ni microstructure in the phenomenological theory of martensite with lattice invariant deformation

Geometrical analysis of interfaces in a Cu-Al-Ni alloy is performed on the basis of the phenomenological theory of martensite. The austenite-martensite interfaces in the foils of the Cu-Al-Ni alloy are faceted. In order to assess possible facet planes, lattice invariant deformation in the form of a simple shear is included into the phenomenological theory. The experimentally observed normals to the facet planes lie in the predicted regions. Experimentally observed lines in the intervariant interfaces are interpreted as slip steps. The directions of these lines agree with theoretical predictions. Note to the reader: On page 03010-p2 several mistakes have been corrected on October 19, 2009

Topological Model of Austenite-Martensite Interfaces in Cu-Al-Ni Alloy

Discussion of the austenite-single-variant martensite interfaces in Cu-Al-Ni alloy is performed in the frame of a topological model of martensite interfaces. This model takes into account admissible defects lying in the interface. The results are compared with the experimental data obtained on the foils of Cu-Al-Ni alloys deformed in situ in a transmission electron microscope

ACTA PHYSICA POLONICA A Displacive Phase Transformations and Generalized Stacking Faults

The displacive phase transformations can be considered as composed of two processes, namely, pure displacements, shuing or shearing of atomic planes, and supplementary homogeneous lattice deformation changing also the dimensions of the moving planes. Such deformation causes shape memory eect when the structural transformation is reversed. General displacements of atomic planes will be examined, i.e. γ-surface type calculations will be reported for single plane shuing, alternate shuing of every other bcc atomic plane and successive displacements of parallel atomic planes producing in combination with homogeneous deformation the close packed structures. The results of calculations using the many-body potentials of the FinnisSinclair type will be compared with ab initio calculations that indicate in which way the phase transformation can be initiated

Displacive Phase Transformations and Generalized Stacking Faults

The displacive phase transformations can be considered as composed of two processes, namely, pure displacements, shuffling or shearing of atomic planes, and supplementary homogeneous lattice deformation changing also the dimensions of the moving planes. Such deformation causes shape memory effect when the structural transformation is reversed. General displacements of atomic planes will be examined, i.e. γ-surface type calculations will be reported for single plane shuffling, alternate shuffling of every other bcc atomic plane and successive displacements of parallel atomic planes producing in combination with homogeneous deformation the close packed structures. The results of calculations using the many-body potentials of the Finnis-Sinclair type will be compared with ab initio calculations that indicate in which way the phase transformation can be initiated