Changes in distributions of grain boundary diffusion properties after grain growth in austenitic steel

1989 ◽  
Vol 112 ◽  
pp. 199-204 ◽  
Author(s):  
Z. Pakieła ◽  
M. Krasnowski ◽  
J.W. Wyrzykowski
Keyword(s):  
Grain Boundary ◽  
Austenitic Steel ◽  
Grain Growth ◽  
Boundary Diffusion ◽  
Grain Boundary Diffusion ◽  
Diffusion Properties

Simulation of Microstructural Evolution during Superplastic Deformation

1999 ◽  
Vol 601 ◽  
Author(s):  
B.-N. Kim ◽  
K. Hiraga
Keyword(s):  
Aspect Ratio ◽  
Grain Boundary ◽  
Grain Growth ◽  
Boundary Diffusion ◽  
Tensile Deformation ◽  
Grain Boundary Diffusion ◽  
Initial Value ◽  
The Matrix ◽  
Dynamic Growth ◽  
Equiaxed Grains

AbstractSuperplastic tensile deformation is simulated in 2 dimensions by incorporating grain boundary diffusion and concurrent grain growth derived from static and dynamic growth mechanisms. The following relationship is found between microstructural changes and deformation behavior for constant stress conditions. Grain boundary diffusion produces an increase in the aspect ratio of the matrix grains during deformation and the increased aspect ratio causes a change in creep rate parameters: the stress exponent is decreased from the initial value of 1.0 for equiaxed grains and the grain size exponent is increased from the initial value of 3.0. Accelerated grain growth is also found by the present simulation.

Diffusion Mechanisms in Nanocrystalline and Nanolaminated Au-Cu

2007 ◽  
Vol 266 ◽  
pp. 13-28 ◽  
Author(s):  
Alan F. Jankowski
Keyword(s):  
Low Temperature ◽  
Grain Boundary ◽  
Grain Growth ◽  
Boundary Diffusion ◽  
Bulk Diffusion ◽  
Grain Boundary Diffusion ◽  
Dominant Mechanism ◽  
Temperature Range ◽  
Diffusion Mechanisms ◽  
Kinetics Of

Thermal anneal treatments are used to identify the temperature range of the two dominant diffusion mechanisms – bulk and grain boundary. To assess the transition between mechanisms, the low temperature range for bulk diffusion is established utilizing the decay of static concentration waves in composition-modulated nanolaminates. These multilayered structures are synthesized using vapor deposition methods as thermal evaporation and magnetron sputtering. However, at low temperature the kinetics of grain-boundary diffusion are much faster than bulk diffusion. The synthesis of Au-Cu alloys (0-20 wt.% Cu) with grain sizes as small as 5 nm is accomplished using pulsed electro-deposition. Since the nanocrystalline grain structure is thermally unstable, these structures are ideal for measuring the kinetics of grain boundary diffusion as measured by coarsening of grain size with low temperature anneal treatments. A transition in the dominant mechanism for grain growth from grain boundary to bulk diffusion is found with an increase in temperature. The activation energy for bulk diffusion is found to be 1.8 eV·atom-1 whereas that for grain growth at low temperatures is only 0.2 eV·atom-1. The temperature for transitioning from the dominant mechanism of grain boundary to bulk diffusion is found to be 57% of the alloy melt temperature and is dependent on composition.

Oxygen Diffusion along Symmetric [0001] Tilt Grain Boundaries in α-Alumina

2006 ◽  
Vol 317-318 ◽  
pp. 415-418 ◽  
Author(s):  
Tsubasa Nakagawa ◽  
Isao Sakaguchi ◽  
Katsuyuki Matsunaga ◽  
Takahisa Yamamoto ◽  
Hajime Haneda ◽  
...  
Keyword(s):  
Grain Boundary ◽  
Grain Boundaries ◽  
Oxygen Diffusion ◽  
Isotopic Exchange ◽  
Boundary Diffusion ◽  
Depth Profiling ◽  
Grain Boundary Diffusion ◽  
Symmetric Tilt ◽  
And Diffusion ◽  
Diffusion Properties

Grain boundary diffusion coefficients of oxygen (δDgb) at 1793K in high purity α-alumina bicrystals with Σ7{2 _ ,310}/[0001] and Σ31{7 _ ,1140}/[0001] symmetric tilt grain boundaries were measured by means of the isotopic exchange and diffusion depth profiling using SIMS. δDgb of both grain boundaries were determined to be 7.1x10-24 [m3/sec] for Σ7 grain boundary and 5.3 x10-24 [m3/sec] for Σ31 grain boundary, respectively. These results indicate that Σ values do not directly relate to grain boundary diffusion properties.

Generalization of Fisher Model for Periodically Non-Uniform Grain Boundary

2008 ◽  
Vol 277 ◽  
pp. 213-220
Author(s):  
V.L. Gapontsev ◽  
Valerie M. Koloskov ◽  
M.G. Gapontseva
Keyword(s):  
Grain Boundary ◽  
Laplace Transform ◽  
Concentration Profile ◽  
Impurity Concentration ◽  
Boundary Diffusion ◽  
Grain Boundary Diffusion ◽  
Tracer Concentration ◽  
Fisher Model ◽  
Definition Of ◽  
Diffusion Properties

The problem of grain boundary diffusion for a case of boundary grain with periodic heterogeneity diffusion properties is considered. Dependence of Laplace transform images of impurity concentration on various diffusion conductivity places is built. The dimensionless parameters, forming the system of grain boundary diffusion regimes are determined. The space (ln x,lnt,1/T) is divided into areas in which the ratio ln ln ~ ln ln ( / ) ln eff o C r x−k t− Q RT − A is maintained, when the parameters of diffusion regime are constant. The values of parameters , , , eff o r k Q A fully specify the diffusion regimes. On this base the new concept for the definition of grain boundary diffusion regimes is carried out and the method for construction of simplified tracer concentration profile is proposed.

Reactionary Interaction as the Basis of Occurrence Heterogeneity Diffusion Properties Grain Boundaries in Polycrystalline Silver

2008 ◽  
Vol 277 ◽  
pp. 221-226
Author(s):  
Valerie M. Koloskov ◽  
V.L. Gapontsev
Keyword(s):  
Grain Boundary ◽  
Data Processing ◽  
Grain Boundaries ◽  
Boundary Diffusion ◽  
Grain Boundary Diffusion ◽  
Primary Data ◽  
Tail Part ◽  
Fisher Model ◽  
Polycrystalline Silver ◽  
Diffusion Properties

The new way of calculation of segregation enthalpy on the basis of grain boundary diffusion data is offered. It proceeds from the primary data on an interval "B"- regime of grain boundary diffusion. For data processing we used the expression for coefficient of grain boundary diffusion got by Borisov and Lubov according to Fisher model for a tail part of the concentration curve. To approve this approach the data of tellurium diffusion in grain boundary of polycrystalline silver are considered.

Iron Redistribution in Aluminum Thin Films

1993 ◽  
Vol 309 ◽  
Author(s):  
David L. Barr ◽  
G.J. Gualtieri ◽  
C.B. Case ◽  
M.A. Marcus ◽  
W.L. Brown
Keyword(s):  
Thin Films ◽  
Grain Boundary ◽  
Grain Growth ◽  
Deposition Temperature ◽  
Boundary Diffusion ◽  
Grain Boundary Diffusion ◽  
Subsequent Annealing ◽  
Precipitate Formation ◽  
Substrate Interface ◽  
Depth Distributions

AbstractStrongly non uniform Fe depth distributions have been observed in AI(0.13 at% Fe) thin films deposited at temperatures of 350ºC and above. The concentration of Fe is uniform in depth at a deposition temperature of 300ºC but is increasingly enhanced toward the substrate interface at 450ºC. Subsequent annealing produces only a slight redistribution of Fe. The Fe is primarily present as precipitates smaller than 100 nm. A model of grain boundary diffusion of Fe and precipitate formation and grain growth is proposed to explain the observed behavior.

Sign in / Sign up

Export Citation Format

Share Document