A grain-boundary diffusion model of dynamic grain growth during superplastic deformation

1999 ◽  
Vol 47 (12) ◽  
pp. 3433-3439 ◽  
Author(s):  
Byung-Nam Kim ◽  
Keijiro Hiraga ◽  
Yoshio Sakka ◽  
Byung-Wook Ahn
Keyword(s):  
Grain Boundary ◽  
Grain Growth ◽  
Diffusion Model ◽  
Superplastic Deformation ◽  
Boundary Diffusion ◽  
Grain Boundary Diffusion ◽  
Dynamic Grain Growth

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.

Superplasticity in Ultrahigh Carbon (1.6 Pct C) Steel

2007 ◽  
Vol 551-552 ◽  
pp. 199-202 ◽  
Author(s):  
Zhan Ling Zhang ◽  
Yong Ning Liu ◽  
Jie Wu Zhu ◽  
G. Yu
Keyword(s):  
Grain Boundary ◽  
Superplastic Deformation ◽  
Boundary Diffusion ◽  
Grain Boundary Sliding ◽  
Strain Rates ◽  
Ultrahigh Carbon Steel ◽  
Elongation To Failure ◽  
Boundary Sliding ◽  
Dynamic Grain Growth ◽  
Microduplex Structure

Ultrahigh carbon steel containing 1.6 wt pct C was processed to create microduplex structure consisting of fine-spheroidized carbides and fine ferrite grains. Elongation-to-failure tests were conducted at strain rates from 10-4s-1 to 15×10-4s-1, and at temperatures from 600 °C to 850 °C. The steel exhibited superplasticity at and above 700 °C when testing at a strain rate of 10-4s-1, and at 800 °C when testing at strain rates of 7×10-4s-1 and slower. The grains retained the equiaxed shape and initial size during deformation; dynamic grain growth was not observed after superplastic deformation, whereas carbide coarsening was observed. It is concluded that the fine ferrite grains or austensite grains are stabilized by the grain boundary carbides, and grain-boundary sliding controlled by grain boundary diffusion is the principal superplastic deformation mechanism at temperatures in the range of 700-850 °C.

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.

Effects of grain growth on grain-boundary diffusion creep by molecular-dynamics simulation

2004 ◽  
Vol 52 (7) ◽  
pp. 1971-1987 ◽  
Author(s):  
A.J. Haslam ◽  
V. Yamakov ◽  
D. Moldovan ◽  
D. Wolf ◽  
S.R. Phillpot ◽  
...  
Keyword(s):  
Molecular Dynamics ◽  
Molecular Dynamics Simulation ◽  
Grain Boundary ◽  
Grain Growth ◽  
Boundary Diffusion ◽  
Grain Boundary Diffusion ◽  
Dynamics Simulation ◽  
Diffusion Creep
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