An ab initio Investigation on the Effects of Impurity in Aluminum Grain Boundary

2001 ◽  
Vol 699 ◽  
Author(s):  
Guang-Hong Lu ◽  
Tomoyuki Tamura ◽  
Masao Kamiko ◽  
Masanori Kohyama ◽  
Ryoichi Yamamoto
Keyword(s):  
Electronic Structure ◽  
Grain Boundary ◽  
Charge Density ◽  
Ab Initio ◽  
Mobility Model ◽  
Weak Bond ◽  
Impurity Atoms ◽  
Tilt Grain Boundary ◽  
Grain Boundary Embrittlement ◽  
Boundary Embrittlement

AbstractThe electronic structure of AlS9 tilt grain boundary with segregated impurity atoms of Na, Ca, Si and S, respectively, has been investigated by an ab initio pseudopotential method. Na and Ca segregation causes the boundary to expand and the charge density to decrease significantly. There forms several weak bond regions. Si segregation increases the charge density between Si and the neighboring Al atom. There forms a stronger Al-Si bond that is a mixture of covalent and metallic character in the boundary. For S segregation, though there forms the stronger bond between Al and S atom, some Al-S bonds may become weaker than the former Al-Al bonds because of the charge density decrease. It is concluded that the mechanism of Na or Ca-promoted Al grain boundary embrittlement is one kind of ‘decohesion model’, that of Si is ‘bond mobility model’. It can't be decided the embrittlement mechanism by S segregation is classified into ‘bond mobility model’ or ‘decohesion model’.

Al Grain Boundary Embrittlement Promoted by Na Impurity: An ab initio Study

2000 ◽  
Vol 653 ◽  
Author(s):  
Guang-Hong Lu ◽  
Masanori Kohyama ◽  
Rayoichi Yamamoto
Keyword(s):  
Electronic Structure ◽  
Grain Boundary ◽  
Charge Density ◽  
First Principles ◽  
Ab Initio Study ◽  
Impurity Atoms ◽  
Metallic Bond ◽  
Tilt Grain Boundary ◽  
Grain Boundary Embrittlement ◽  
Boundary Embrittlement

AbstractWe calculate the electronic structure of AlΣ9 tilt grain boundary with substitutional Na impurity atoms by first principles pseudopotential method. Results show that by Na segregation Al grain boundary expands and the valence charge density decreases significantly along the boundary. There is no stronger bond than metallic bond in the boundary even with Na impurity. We therefore conclude that the mechanism of Na-promoted Al grain boundary embrittlement should be one kind of ‘decohesion model’.

Investigations of the Bonding Changes Associated with Grain Boundary Embrittlement

1996 ◽  
Vol 458 ◽  
Author(s):  
V. J. Keast ◽  
J. Bruley ◽  
D. B. Williams
Keyword(s):  
Electronic Structure ◽  
Grain Boundary ◽  
Energy Loss ◽  
Grain Boundaries ◽  
Edge Structure ◽  
Grain Boundary Embrittlement ◽  
Impurity Elements ◽  
Electron Energy Loss ◽  
Segregation Of Impurities ◽  
Boundary Embrittlement

ABSTRACTThe embrittlement of materials through the segregation of impurities to the grain boundaries is a common and industrially important problem. Despite considerable investigation, the mechanism by which the impurity elements cause embrittlement is not well understood. A change in the electron energy loss near edge structure (ELNES) has been observed at Cu grain boundaries containing Bi. This result provides experimental evidence that a change in the electronic structure at the grain boundary is responsible for embritdement.

scholarly journals Hydrogen-Promoted Grain Boundary Embrittlement and Vacancy Activity in Metals: Insights from Ab Initio Total Energy Calculatons

2005 ◽  
Vol 46 (4) ◽  
pp. 756-760 ◽  
Author(s):  
Wen-Tong Geng ◽  
Arthur J. Freeman ◽  
Gregory B. Olson ◽  
Yoshitaka Tateyama ◽  
Takahisa Ohno
Keyword(s):  
Grain Boundary ◽  
Total Energy ◽  
Ab Initio ◽  
Grain Boundary Embrittlement ◽  
Boundary Embrittlement

Solute Segregation at Σ11(113)[110] Grain Boundary and Effect of the Segregation on Grain Boundary Cohesion in Aluminum from First Principles

2010 ◽  
Vol 654-656 ◽  
pp. 942-945 ◽  
Author(s):  
Tokuteru Uesugi ◽  
Kenji Higashi
Keyword(s):  
Free Surface ◽  
Grain Boundary ◽  
First Principles ◽  
Solute Segregation ◽  
First Principles Calculations ◽  
Symmetric Tilt ◽  
Tilt Grain Boundary ◽  
Grain Boundary Embrittlement ◽  
Boundary Embrittlement

We investigate the energy of segregation of solute Ca at symmetric tilt grain boundary in aluminum from the first-principles calculations. As energy of segregation of Ca is negative, Ca atoms tend to segregate at the grain boundary. Furthermore, on basis of the Rice-Wang model, we study the effect of the segregation of Ca on the grain boundary embrittlement of aluminum. Our first-principles calculations of energies of segregation at grain boundary and free surface show that Ca behaves as embrittler.

Morphology and atomic structure of segregated grain boundaries in Cu-Sb

1992 ◽  
Vol 50 (1) ◽  
pp. 254-255
Author(s):  
R. W. Fonda ◽  
D. E. Luzzi
Keyword(s):  
Grain Boundary ◽  
Grain Boundaries ◽  
Intergranular Fracture ◽  
Atomic Structure ◽  
Copper Alloys ◽  
Polycrystalline Materials ◽  
Grain Boundary Embrittlement ◽  
Boundary Embrittlement

The properties of polycrystalline materials are strongly dependant upon the strength of internal boundaries. Segregation of solute to the grain boundaries can adversely affect this strength. In copper alloys, segregation of either bismuth or antimony to the grain boundary will embrittle the alloy by facilitating intergranular fracture. Very small quantities of bismuth in copper have long been known to cause severe grain boundary embrittlement of the alloy. The effect of antimony is much less pronounced and is observed primarily at lower temperatures. Even though moderate amounts of antimony are fully soluble in copper, concentrations down to 0.14% can cause grain boundary embrittlement.

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