Computer Modelling of Grain Boundaries for Optimizing the Properties of Polycrystalline Metallic Materials

2009 ◽  
Vol 618-619 ◽  
pp. 207-214 ◽  
Author(s):  
Krzysztof Jan Kurzydlowski
Keyword(s):  
Corrosion Resistance ◽  
Grain Boundaries ◽  
Recent Progress ◽  
Computer Modelling ◽  
Metallic Materials ◽  
Grain Sizes

Grain boundaries significantly influence the properties of polycrystalline metallic materials, particularly with grain sizes in the nano-metre range. The effect of grain boundaries on plasticity, fracture and corrosion resistance is well documented experimentally. The aim of this paper is to show that recent progress in modelling of the role of grain boundaries in metallic materials offers new possibilities for optimizing their properties.

Elucidation of block boundaries as the dissolution channels in hydrated cement

1978 ◽  
Vol 36 (1) ◽  
pp. 484-485
Author(s):  
N.V. Belov ◽  
U.I. Papiashwili ◽  
B.E. Yudovich
Keyword(s):  
Liquid Phase ◽  
Grain Boundaries ◽  
Benzoyl Peroxide ◽  
Phase Contrast ◽  
Active Role ◽  
Point Of View ◽  
Hardened Cement ◽  
Hydrated Cement ◽  
Hardened Cement Paste

It has been almost universally adopted that dissolution of solids proceeds with development of uniform, continuous frontiers of reaction.However this point of view is doubtful / 1 /. E.g. we have proved the active role of the block (grain) boundaries in the main phases of cement, these boundaries being the areas of hydrate phases' nucleation / 2 /. It has brought to the supposition that the dissolution frontier of cement particles in water is discrete. It seems also probable that the dissolution proceeds through the channels, which serve both for the liquid phase movement and for the drainage of the incongruant solution products. These channels can be appeared along the block boundaries.In order to demonsrate it, we have offered the method of phase-contrast impregnation of the hardened cement paste with the solution of methyl metacrylahe and benzoyl peroxide. The viscosity of this solution is equal to that of water.

Observation of secondary slip systems in tungsten bicrystals

1984 ◽  
Vol 42 ◽  
pp. 478-479
Author(s):  
J. R. Fekete ◽  
R. Gibala
Keyword(s):  
Stress Field ◽  
Grain Boundaries ◽  
Deformation Behavior ◽  
Stress Axis ◽  
Polycrystalline Materials ◽  
Slip Systems ◽  
Metallic Materials ◽  
Twist Boundary ◽  
Secondary Slip ◽  
Plane Normal

The deformation behavior of metallic materials is modified by the presence of grain boundaries. When polycrystalline materials are deformed, additional stresses over and above those externally imposed on the material are induced. These stresses result from the constraint of the grain boundaries on the deformation of incompatible grains. This incompatibility can be elastic or plastic in nature. One of the mechanisms by which these stresses can be relieved is the activation of secondary slip systems. Secondary slip systems have been shown to relieve elastic and plastic compatibility stresses. The deformation of tungsten bicrystals is interesting, due to the elastic isotropy of the material, which implies that the entire compatibility stress field will exist due to plastic incompatibility. The work described here shows TEM observations of the activation of secondary slip in tungsten bicrystals with a [110] twist boundary oriented with the plane normal parallel to the stress axis.

Carbide precipitation and chromium depletion on coherent twin boundaries in deformed 304 stainless steels

1992 ◽  
Vol 50 (2) ◽  
pp. 1216-1217
Author(s):  
A.H. Advani ◽  
L.E. Murr ◽  
D.J. Matlock ◽  
W.W. Fisher ◽  
P.M. Tarin ◽  
...  
Keyword(s):  
Grain Boundaries ◽  
Stainless Steels ◽  
Interfacial Free Energy ◽  
Carbide Precipitation ◽  
Twin Boundaries ◽  
Invariant Structure ◽  
Heat Treated ◽  
Constant Structure ◽  
Cr Depletion

Coherent annealing-twin boundaries are constant structure and energy interfaces with an average interfacial free energy of ∼19mJ/m2 versus ∼210 and ∼835mJ/m2 for incoherent twins and “regular” grain boundaries respectively in 304 stainless steels (SS). Due to their low energy, coherent twins form carbides about a factor of 100 slower than grain boundaries, and limited work has also shown differences in Cr-depletion (sensitization) between twin versus grain boundaries. Plastic deformation, may, however, alter the kinetics and thermodynamics of twin-sensitization which is not well understood. The objective of this work was to understand the mechanisms of carbide precipitation and Cr-depletion on coherent twin boundaries in deformed SS. The research is directed toward using this invariant structure and energy interface to understand and model the role of interfacial characteristics on deformation-induced sensitization in SS. Carbides and Cr-depletion were examined on a 20%-strain, 0.051%C-304SS, heat treated to 625°C-4.5h, as described elsewhere.

Role of miRNA in circadian rhythmicity: recent progress

2011 ◽  
Vol 31 (10) ◽  
pp. 1137-1139
Author(s):  
Qing-min WANG ◽  
Hui WAN ◽  
Fen-zhou SHI ◽  
Jun SHEN ◽  
Qiu-hong LIU
Keyword(s):  
Recent Progress ◽  
Circadian Rhythmicity

Recent Progress in the Therapeutic Role of Serelaxin in Vascular Dysfunction

2018 ◽  
Vol 19 (11) ◽  
pp. 1079-1087 ◽  
Author(s):  
Ghulam Murtaza ◽  
Adeel Siddiqui ◽  
Izhar Hussain
Keyword(s):  
Recent Progress ◽  
Vascular Dysfunction ◽  
Therapeutic Role

Effect of grain size on the vapour phase hydration of monoclinic and triclinic modifications of tricalcium silicate; role of high temperature activation

1991 ◽  
Vol 56 (10) ◽  
pp. 1993-2008
Author(s):  
S. Hanafi ◽  
G. M. S. El-Shafei ◽  
B. Abd El-Hamid
Keyword(s):  
Particle Size ◽  
Vapour Phase ◽  
Tricalcium Silicate ◽  
Active Centers ◽  
Thermally Activated ◽  
Grain Sizes ◽  
Intermediate Size ◽  
Surface Active ◽  
Temperature Activation

The hydration of tricalcium silicate (C3S) with three grain sizes of monoclinic (M) and triclinic (T) modifications and on their thermally activated samples were investigated by exposure to water vapour at 80°C for 60 days. The products were investigated by XRD, TG and N2 adsorption. The smaller the particle size the greater was the hydration for both dried and activated samples from (M). In the activated samples a hydrate with 2θ values of 38.4°, 44.6° and 48.6° could be identified. Hydration increased with particle size for the unactivated (T) samples but after activation the intermediate size exhibited enhanced hydration. Thermal treatment at 950°C of (T) samples increased the surface active centers on the expense of those in the bulk. Changes produced in surface texture upon activation and/or hydration are discussed.

scholarly journals The role of alloyed strontium in the microstructures and alkaline electrochemistry of Mg–5Al–4Sn alloys

RSC Advances ◽  
2020 ◽  
Vol 10 (57) ◽  
pp. 34387-34395
Author(s):  
Le Van Sy ◽  
Phan Minh Quoc Binh ◽  
Bhajan Lal ◽  
Quy Bau Nguyen ◽  
Tran Van Hung ◽  
...  
Keyword(s):  
Corrosion Resistance ◽  
Pitting Corrosion ◽  
Die Casting ◽  
Pitting Corrosion Resistance

The development of Mg–5Al–4Sn–xSr alloys with α-grain reduction, refined precipitates and pitting corrosion resistance by die casting.

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