Deformation twins have been reported to produce high strength and ductility. Intersections of deformation twins may affect the microstructural evolution during plastic deformation and consequently influence mechanical properties. However, the mechanisms governing twin-intersection behavior remain poorly understood. In this study, we investigated twin intersection mechanisms by observing twin tr...

The atomistic mechanisms active during plastic deformation of nanocrystalline metals are still a subject of controversy. The recently developed approach of combining automated crystal orientation mapping (ACOM) and in situ straining inside a transmission electron microscope was applied to study the deformation of nanocrystalline Pd x Au1- x thin films. This combination enables direct imaging of...

In the present study, we perform molecular dynamic simulations to investigate the compression response and atomistic deformation mechanisms of twinned nanospheres. The relationship between load and compression depth is calculated for various twin spacing and loading directions. Then, the overall elastic properties and the underlying plastic deformation mechanisms are illuminated. Twin boundarie...

– The (21̄1̄)〈111〉 twinning energy landscape of BCC Mo is determined using the density functional theory for embryos containing 2 to 7 layers. The 2-layer embryo is metastable, whereas the 3and 4-layer ones are unstable. Layer-by-layer growth starts at 5 layers. The twin boundary formation and migration energies are found to be 607mJ/m and 40mJ/m, respectively, indicating that twin partial disloc...

Title of dissertation: MODELING THE INFLUENCE OF PHASE BOUNDARIES AND OXYGEN INTERSTITIALS ON THE NUCLEATION AND GROWTH OF DEFORMATION TWINS IN THE ALPHA-PHASE OF TITANIUM ALLOYS William Joseph Joost, Doctor of Philosophy, 2015 Dissertation directed by: Professor Sreeramamurthy Ankem Professor Maija M. Kuklja Department of Materials Science and Engineering Twinning is an important deformation m...

The strength and ductility of nanolayered materials are determined by a delicate balance between dislocation and interface motion under applied mechanical loading. We present here studies of dislocation and interface motion in single crystal and nanotwinned copper, utilizing molecular dynamics simulations. Motion of twin boundary interfaces themselves is dictated by the stress state at the inte...

Magnesium alloys exhibit complex deformation related mechanical behavior, viz. plastic anisotropy, tension-compression asymmetry and premature failure. Their origins are in the underlying heterogeneous deformation due to dislocation slip and deformation twinning on different crystallographic systems. The twin formations lead to microstructure evolution, strain localization and initiation of sho...

An equiatomic FeCoCrNi high-entropy alloy with a face-centered cubic structure was fabricated by a powder metallurgy route, and then processed by high-pressure torsion. Detailed microscopy investigations revealed that grain refinement from coarse grains to nanocrystalline grains occurred mainly via concurrent nanoband (NB) subdivision and deformation twinning. NB-NB, twin-NB and twin-twin inter...

This paper analyses slip transfer at the boundary of nanoscaled growth twins in face-centred cubic (f.c.c.) metals for strengthening mechanism. The required stress for slip transfer, i.e. inter-twin flow stress, is obtained in a simple expression in terms of stacking fault energy and/or twin boundary (TB) energy, constriction energy and activation volume. For nanotwinned Al, Cu and Ni, inter-tw...