Characteristic boundaries associated with three-dimensional twins in hexagonal metals.

Twinning is a critically important deformation mode in hexagonal close-packed metals. Twins are three-dimensional (3D) domains, whose growth is mediated by the motion of facets bounding the 3D twin domains and influences work hardening in metals. An understanding of twin transformations therefore necessitates that the atomic-scale structure and intrinsic mobilities of facets be known and characterized.

The critical role of grain orientation and applied stress in nanoscale twinning.

Numerous recent studies have focused on the effects of grain size on deformation twinning in nanocrystalline fcc metals. However, grain size alone cannot explain many observed twinning characteristics. Here we show that the propensity for twinning is dependent on the applied stress, grain orientation and stacking fault energy.

Engineering interface structures and thermal stabilities via SPD processing in bulk nanostructured metals.

Nanostructured metals achieve extraordinary strength but suffer from low thermal stability, both a consequence of a high fraction of interfaces. Overcoming this tradeoff relies on making the interfaces themselves thermally stable. Here we show that the atomic structures of bi-metal interfaces in macroscale nanomaterials suitable for engineering structures can be significantly altered via changing the severe plastic deformation (SPD) processing pathway.

Analysis of recrystallized volume fractions in uranium using electron backscatter diffraction.

Electron backscatter diffraction was used to examine the recrystallization behaviour of warm, clock-rolled uranium. A new uranium preparation method was developed, resulting in acceptable specimen surface finishes nearly every time, even for as-rolled specimens. Recrystallized fractions were differentiated from unrecrystallized fractions using differences in the grain average misorientation, a measure of the internal level of misorientation within a grain.

A single-tilt TEM stereomicroscopy technique for crystalline materials.

A new single-tilt technique for performing TEM stereomicroscopy of strain fields in crystalline materials has been developed. The technique is a weak beam technique that involves changing the value of g and/or s g while tilting across a set of Kikuchi bands. The primary benefit of the technique is it can be used with single-tilt TEM specimen holders including many specialty holders such as in situ straining, heating, and cooling holders.