The role of grain size and the presence of low and high angle grain boundaries in the deformation mechanism of nanophase Ni: A molecular dynamics computer simulation

ABSTRACTMolecular dynamics computer simulation of nanocrystalline Ni and Cu with mean grain sizes ranging from 5 to 20 nm show that grain boundaries in nanocrystalline metals have structures similar to most grain boundaries found in conventional polycrystalline materials. Moreover, the excess enthalpy density in grain boundaries and triple junctions appears to be independent of grain in both, computer generated and experimental measured samples. Simulations of deformation under constant uniaxial stress demonstrate a change in deformation mechanism as function of grain size: at the smallest grain sizes all deformation is accommodated in the grain boundaries, at higher grain sizes, intragrain deformation is observed

Download Full-text

EBSD Analysis of Friction Stir Welded 7136-T76 Aluminum Alloy

Solid State Phenomena ◽

10.4028/www.scientific.net/ssp.203-204.258 ◽

2013 ◽

Vol 203-204 ◽

pp. 258-261 ◽

Cited By ~ 2

Author(s):

Izabela Kalemba ◽

Krzysztof Muszka ◽

Mirosław Wróbel ◽

Stanislaw Dymek ◽

Carter Hamilton

Keyword(s):

Grain Size ◽

Aluminum Alloy ◽

Grain Boundaries ◽

Texture Analysis ◽

Crystallographic Texture ◽

High Frequency ◽

The Other ◽

Ebsd Analysis ◽

High Angle ◽

Friction Stir

This research addresses the EBSD analysis of friction stir welded 7136-T76 aluminum alloy. The objectives of this study were to evaluate the grain size and their shape, character of grain boundaries in the stirred and thermo-mechanically affected zones, both on the advancing and retreating side as well as to investigate changes in the crystallographic texture. Results of texture analysis indicate the complexity of the FSW process. The texture gradually weakens on moving from the thermo-mechanically affected zone toward the weld center. The stirred zone is characterized by very weak texture and is dominated by high angle boundaries. On the other hand, the thermo-mechanically affected zone exhibits a high frequency of low angle boundaries.

Download Full-text

Molecular Dynamics Study on Deformation Mechanism of Grain Boundaries in Magnesium Crystal: Based on Coincidence Site Lattice Theory

Journal of Materials ◽

10.1155/2018/4153464 ◽

2018 ◽

Vol 2018 ◽

pp. 1-10 ◽

Cited By ~ 1

Author(s):

Ken-ichi Saitoh ◽

Kohei Kuramitsu ◽

Tomohiro Sato ◽

Masanori Takuma ◽

Yoshimasa Takahashi

Keyword(s):

Molecular Dynamics ◽

Deformation Mechanism ◽

Coincidence Site Lattice ◽

Md Simulations ◽

Uniaxial Tensile ◽

High Angle ◽

Site Lattice ◽

Embedded Atom ◽

Significant Difference ◽

Eam Potential

As for magnesium (Mg) alloys, it has been noted that they are inferior to plastic deformation, but improvement in the mechanical properties by further refinement of grain size has been recently suggested. It means the importance of atomistic view of polycrystalline interface of Mg crystal. In this study, to discuss the deformation mechanism of polycrystalline Mg, atomistic grain boundary (GB) models by using coincidence site lattice (CSL) theory are constructed and are simulated for their relaxed and deformatted structures. First, GB structures in which the axis of rotation is in [11¯00] direction are relaxed at 10 Kelvin, and the GB energies are evaluated. Then, the deformation mechanism of each GB model under uniaxial tensile loading is observed by using the molecular dynamics (MD) method. The present MD simulations are based on embedded atom method (EAM) potential for Mg crystal. As a result, we were able to observe atomistically a variety of GB structures and to recognize significant difference in deformation mechanism between low-angle GBs and high-angle GBs. A close scrutiny is made on phenomena of dislocation emission processes peculiar to each atomistic local structure in high-angle GBs.

Download Full-text