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Very many structural materials like metals and ceramics are of
crystalline nature.Undermostoftheconditions,
theyundergoplasticdeformationbefore they fail under load. The
plastic deformation is mediated by the gene- tion and motion of
one-dimensional crystal defects, the so-called dislocations. Thus,
the density and dynamic properties of the dislocations determine
the plastic behavior of the respective materials and frequently
also their failure. Thedislocationdynamics, that is, the
responseofthedislocationsto anext- nal load, is controlled by the
interaction between the moving dislocations with the periodic
crystal lattice structure, other crystal defects from point defects
oversmall clusters to largerprecipitates, with other dislocations
fo- ing a microstructure through which the mobile dislocations have
to move, and ?nally the grain and phase structure of the material.
Considering these di?erent interactions, the dislocation motion
turns out to be quite a complex process. In situ straining
experiments in a transmission electron microscope are a powerful
means for studying the microprocesses controlling the dislocation
mobility. With this method, dislocations candirectly be
observedduring their
motionunderload.Thetechniqueadvancedwhenhigh-voltageelectronmic-
scopes became commercially available at the end of the 1960s, ?rst
in Japan and later on also in other countries. These microscopes
enable the transm- sion of thicker specimens, which have properties
similar to macroscopic bulk specimens.Besides, they
o?ersu?cientroomfor elaboratedeformationstages in the specimen
chamber. In the last 30 years, in situ straining experiments were
performed on many materials, both in conventional and in
high-voltage electron microscopes. The present author and his
coworkers performed such experiments over about 30 years, yielding
many hours of video recordings of dislocation mot
Very many structural materials like metals and ceramics are of
crystalline nature.Undermostoftheconditions,
theyundergoplasticdeformationbefore they fail under load. The
plastic deformation is mediated by the gene- tion and motion of
one-dimensional crystal defects, the so-called dislocations. Thus,
the density and dynamic properties of the dislocations determine
the plastic behavior of the respective materials and frequently
also their failure. Thedislocationdynamics, that is, the
responseofthedislocationsto anext- nal load, is controlled by the
interaction between the moving dislocations with the periodic
crystal lattice structure, other crystal defects from point defects
oversmall clusters to largerprecipitates, with other dislocations
fo- ing a microstructure through which the mobile dislocations have
to move, and ?nally the grain and phase structure of the material.
Considering these di?erent interactions, the dislocation motion
turns out to be quite a complex process. In situ straining
experiments in a transmission electron microscope are a powerful
means for studying the microprocesses controlling the dislocation
mobility. With this method, dislocations candirectly be
observedduring their
motionunderload.Thetechniqueadvancedwhenhigh-voltageelectronmic-
scopes became commercially available at the end of the 1960s, ?rst
in Japan and later on also in other countries. These microscopes
enable the transm- sion of thicker specimens, which have properties
similar to macroscopic bulk specimens.Besides, they
o?ersu?cientroomfor elaboratedeformationstages in the specimen
chamber. In the last 30 years, in situ straining experiments were
performed on many materials, both in conventional and in
high-voltage electron microscopes. The present author and his
coworkers performed such experiments over about 30 years, yielding
many hours of video recordings of dislocation mot
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