scholarly journals Effects of Zn and Mg Segregations on the Grain Boundary Sliding and Cohesion in Al: Ab Initio Modeling

Metals ◽  
2021 ◽  
Vol 11 (4) ◽  
pp. 631
Author(s):  
Andrey Kuznetsov ◽  
Lidia Karkina ◽  
Yuri Gornostyrev ◽  
Pavel Korzhavyi
Keyword(s):  
Grain Boundary ◽  
Ab Initio ◽  
Strong Relationship ◽  
Shear Resistance ◽  
Grain Boundary Sliding ◽  
Cohesive Properties ◽  
Segregation Process ◽  
Boundary Sliding ◽  
Solute Atoms ◽  
Experimental Findings

The formation of Zn and Mg segregations at a tilt Σ5{013} <100> grain boundary (GB) in Al and the effects of these solutes on deformation behavior of polycrystalline Al were investigated using ab initio total energy calculations. Using a step-by-step modeling of the segregation process, we found that the formation of a thick segregation layer of Zn at the GB is energetically preferable, while the formation of an atomically thin segregation layer is expected in the case of Mg. To reveal the effect of segregation on the cohesive properties of Al GBs, we calculated the energy of cleavage decohesion and the shear resistance for GB sliding. We show that the segregation of Zn results in a substantial decrease in barriers for GB sliding, while the segregation of Mg increases the barriers. The results obtained allow us to explain experimental findings and demonstrate a strong relationship between chemical bonding of solute atoms, their segregation ability, and GB strength.

Role of Vacancies and Solute Atoms on Grain Boundary Sliding

1999 ◽  
Vol 601 ◽  
Author(s):  
J.S. Vetrano ◽  
C.H. Henager ◽  
E.P. Simonen
Keyword(s):  
Grain Boundary ◽  
Solute Atom ◽  
Vacancy Concentration ◽  
Grain Boundary Sliding ◽  
Fine Grained ◽  
Grain Boundary Plane ◽  
Transmission Electron ◽  
Boundary Sliding ◽  
Solute Atoms

AbstractIt is necessary for grain boundary dislocations to slide and climb during the grain boundary sliding process that dominates fine-grained superplastic deformation. The process of climb requires either an influx of vacancies to the grain boundary plane or a local generation of vacancies. Transmission electron microscopy (TEM) observations of grain boundaries in superplastically deformed Al-Mg-Mn alloys quenched under load from the deformation temperature have revealed the presence of nano-scale cavities resulting from a localized supersaturation of vacancies at the grain boundary. Compositional measurements along interfaces have also shown an effect of solute atoms on the local structure. This is shown to result from a coupling of vacancy and solute atom flows during deformation and quenching. Calculations of the localized vacancy concentration indicate that the supersaturation along the grain boundary can be as much as a factor often. The effects of the local supersaturation and solute atom movement on deformation rates and cavity nucleation and growth will be discussed.

Ab Initio Investigation of Grain Boundary Sliding

1995 ◽  
Vol 408 ◽  
Author(s):  
M. C. Payne ◽  
G. P. Francis ◽  
C. Molteni ◽  
N. Marzari ◽  
V. Deyirmenjian ◽  
...  
Keyword(s):  
Grain Boundary ◽  
Total Energy ◽  
Ab Initio ◽  
Grain Boundary Sliding ◽  
Microscopic Level ◽  
Extensive Investigation ◽  
Preliminary Results ◽  
Pseudopotential Calculations ◽  
Covalently Bonded ◽  
Boundary Sliding

AbstractWe are using total energy pseudopotential calculations to carry out an extensive investigation into grain boundary sliding in a number of different systems, in order to understand, at microscopic level, the fundamental mechanisms responsible for this process.In this paper we present results for the sliding process at the ∑ = 5(001) twist grain boundary in germanium, chosen as a typical covalently bonded material, and contrast them with preliminary results obtained for the ∑ = 5 (001) twist grain boundary in aluminium, a typical metal.

Grain boundary sliding: an ab initio simulation

1996 ◽  
Vol 37 (1-3) ◽  
pp. 121-126 ◽  
Author(s):  
C. Molteni ◽  
O.P. Francis ◽  
M.C. Payne ◽  
V. Heine
Keyword(s):  
Grain Boundary ◽  
Ab Initio ◽  
Grain Boundary Sliding ◽  
Ab Initio Simulation ◽  
Boundary Sliding

Examination of Fracture Interfaces in Silicon Nitride

1975 ◽  
Vol 33 ◽  
pp. 60-61
Author(s):  
Nancy J. Tighe
Keyword(s):  
Silicon Nitride ◽  
Grain Boundary ◽  
Crack Growth ◽  
Subcritical Crack Growth ◽  
Slow Crack Growth ◽  
Ceramic Materials ◽  
Grain Boundary Sliding ◽  
Boundary Phase ◽  
Turbine Engines ◽  
Boundary Sliding

Silicon nitride is one of the ceramic materials being considered for the components in gas turbine engines which will be exposed to temperatures of 1000 to 1400°C. Test specimens from hot-pressed billets exhibit flexural strengths of approximately 50 MN/m2 at 1000°C. However, the strength degrades rapidly to less than 20 MN/m2 at 1400°C. The strength degradition is attributed to subcritical crack growth phenomena evidenced by a stress rate dependence of the flexural strength and the stress intensity factor. This phenomena is termed slow crack growth and is associated with the onset of plastic deformation at the crack tip. Lange attributed the subcritical crack growth tb a glassy silicate grain boundary phase which decreased in viscosity with increased temperature and permitted a form of grain boundary sliding to occur.

INTERNAL FRICTION PEAKS CONNECTED WITH GRAIN BOUNDARY SLIDING IN Al

1983 ◽  
Vol 44 (C9) ◽  
pp. C9-759-C9-764
Author(s):  
E. Bonetti ◽  
A. Cavallini ◽  
E. Evangelista ◽  
P. Gondi
Keyword(s):  
Internal Friction ◽  
Grain Boundary ◽  
Grain Boundary Sliding ◽  
Boundary Sliding
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