Effects of Electropulsing Treatment on the Precipitation Behaviour of Grain Boundary Carbides in GH3044 Alloy

2010 ◽  
Vol 654-656 ◽  
pp. 464-467 ◽  
Author(s):  
Yang Liu ◽  
Lei Wang ◽  
Yu Chen Wang ◽  
Hong Yan Liu ◽  
Xue Jiao Chen ◽  
...  
Keyword(s):  
Grain Boundary ◽  
Current Density ◽  
Pulse Width ◽  
High Current Density ◽  
Aging Treatment ◽  
Volume Percentage ◽  
Precipitation Behaviour ◽  
M23c6 Type ◽  
Type Carbide ◽  
Electropulsing Treatment

The effects of electropulsing treatment on the precipitation behaviour of grain boundary carbides in GH3044 alloy were investigated. The results showed that the initial temperature of precipitation of M23C6 type carbides on grain boundary could be decreased by electropulsing treatment under the condition of high current density of 10.0kA/mm2 with a frequency of 5Hz and pulse width of 15s. The volume percentage of M23C6 type carbide was greatly increased to 274.60% comparing with that of the aging treatment at the same temperature. However, the precipitation of M23C6 type carbide was inhibited by electropulsing treatment under the condition of high frequency of 45Hz with the current density of 2kA/mm2 and pulse width of 15s. The volume percentage of M23C6 type carbide was decreased to 18.81% comparing with that of the aging treatment at the same temperature. It has been found that the diffusion of solute atom in the alloy can be promoted by the electric effect with the electropulsing. As a result, the thermodynamic condition and kinetics of the precipitation of M23C6 type carbide were changed, and both the initial and peak temperatures of precipitation were decreased.

Precipitation of Nano-Sized Z-Phase in HR3C Austenitic Heat Resistant Steel

2013 ◽  
Author(s):  
Fengshi Yin ◽  
Zhen Xu ◽  
Bing Xue ◽  
Li Zhou ◽  
Xuebo Jiang
Keyword(s):  
Aging Temperature ◽  
Solution Treatment ◽  
Aging Treatment ◽  
Resistant Steel ◽  
Secondary Phases ◽  
Heat Resistant Steel ◽  
Heat Resistant ◽  
M23c6 Type ◽  
Type Carbide ◽  
Austenite Grains

Effect of heat treatment on the precipitation behavior of secondary phases in a HR3C austenitic heat resistant steel was investigated. The microstructure of the steel in solution-treated state consists of austenitic matrix and coarse Z-phase particles. After aging treatment at 650–950°C for 1h, M23C6-type carbide precipitates along random grain boundaries. Dense and homogeneous nanosized Z-phase precipitates within austenite grains are obtained by an aging treatment at a temperature between 800 and 900°C for 1h. The high density of dislocation walls produced during the water-cooling process after solution treatment facilitate the precipitation of the nanosized Z-phase. With increasing the aging temperature, the hardness initially drops, then increases and reaches a peak when the aging temperature is at 850°C due to the precipitation of the nanosized Z-phase.

Texture Evolution along the Layer Thickness in a Fe-3%Si Steel under Electropulsing Treatment

2011 ◽  
Vol 702-703 ◽  
pp. 943-946 ◽  
Author(s):  
Xin Li Wang ◽  
Hong Ming Zhao ◽  
Wen Bin Dai ◽  
Xiang Zhao
Keyword(s):  
Layer Thickness ◽  
Current Density ◽  
High Current Density ◽  
Texture Evolution ◽  
Specimen Thickness ◽  
Evolution Analysis ◽  
Orientation Density ◽  
Current Densities ◽  
The Difference ◽  
Electropulsing Treatment

Effects of electric current densities on recrystallization texture evolution in cold-rolled Fe-3%Si steel were investigated by using a high current density electropulsing treatment. Results showed that the orientation density of α fiber and  fiber varied with the specimen thickness during current passing. However, with the current density increasing, the difference from layer thickness almost vanished. In addition, Goss component texture was the final sharper one but no relation with the specimen thickness at 9.96kAmm-2. By the texture evolution analysis, it was found that the preferred nucleation always occurred in the surface layer due to the high storied energy coursed by previous cold rolling. Combined with the corresponding microstructures, it could be found that though there was an apparent texture evolution along specimen thickness, the microstructure had no change with thickness. In addition, due to the application of electropulsing, the recrystallization nucleation was greatly increased.

Formation of nanophases in a Cu–Zn alloy under high current density electropulsing

2000 ◽  
Vol 15 (10) ◽  
pp. 2065-2068 ◽  
Author(s):  
W. Zhang ◽  
M. L. Sui ◽  
K. Y. Hu ◽  
D. X. Li ◽  
X. N. Guo ◽  
...  
Keyword(s):  
Current Density ◽  
High Current Density ◽  
High Energy ◽  
Coarse Grained ◽  
High Current ◽  
Transmission Electron ◽  
Average Grain Size ◽  
Before And After ◽  
Electropulsing Treatment ◽  
Zn Alloy

The microstructure of samples before and after a high current density electropulsing treatment was characterized by using high-resolution transmission electron microscopy. It has been found that in the coarse-grained Cu–Zn alloy subjected to the electropulsing treatment, two nanophases were formed, α–Cu(Zn) and β′–(CuZn), the average grain size of which is about 11 nm. A possible mechanism for the formation of nanophases was proposed. The experimental results indicated that electropulsing, as an instantaneous high-energy input, plays an important role in the nonequilibrium microstructural changes in materials and serves as a potential processing approach to synthesize nanostructured materials.

Grain Boundary Grooving as the Mechanism of the Blech Electromigration in Interconnects

1995 ◽  
Vol 391 ◽  
Author(s):  
E.E. Glickman ◽  
L.M. Klinger
Keyword(s):  
Grain Boundary ◽  
Surface Diffusion ◽  
Current Density ◽  
High Current Density ◽  
Diffusion Flux ◽  
Stress Gradient ◽  
Displacement Velocity ◽  
Gradual Transition ◽  
Flux Divergence ◽  
New Approach

AbstractWe present a new approach to understand the mechanism of "homogeneous", or Blech electromigration (EM). This phenomenon describes macroscopically homogeneous displacement of the up-wind edge of thin film lines in microelectronic devices and is responsible for openings at contact windows, "vias" and other sites of perfect diffusion flux divergence.Our SEM, EPMA and EM drift velocity experiments have revealed the gradual transition from the microscopically homogeneous EM displacement to the highly nonhomogeneous mode wherein copious islands of residual material remain behind the drifting cathode edge of aluminum stripes. The transition is shown to occur due to an increase in either the current density, j, or in the stripe length, 1. The latter case suggests, that the transition results from the growth of the net grain boundary (GB) diffusion flux, I=le-Ib ,where Ie∝j and 1b∝1/1 are the EM flux and stress-gradient-driven back flux, respectively.Based upon recent progress in the theory of GB grooving under "external" GB fluxes, with surface diffusion acting as the healing mechanism, grooves' propagation along the line and their merging is considered to be the micromechanism of the "homogeneous" EM. In terms of the simple model described, the transition from the slow receding of the cathode butt edge slightly wrinkled by shallow grooves (A-regime of EM) to the fast extension and merging of slot -like grooves (B-regime) accounts for the transition observed in EM mode, while in both regimes the EM displacement velocity, V, is presumed to represent the groove propagation rate.The theory developed reduces to Blech formulae for V for the truly homogeneous A-regime and predicts quite different EM kinetics for the B-regime of microscopically nonhomogeneous EM. The latter is expected to dominate for films loaded by high current density with large grains and low surface diffusion.The dependence obtained for the residual mass left behind the drifted edge vs the displacement velocity, V, for unpassivated aluminum stripes of various lengths, loaded by j=2-106 A/cm2 at 548K provides a good evidence in support of a new approach.

Formation of a Nanostructure in a Low-carbon Steel Under High Current Density Electropulsing

2002 ◽  
Vol 17 (5) ◽  
pp. 921-924 ◽  
Author(s):  
Yizhou Zhou ◽  
Wei Zhang ◽  
Manling Sui ◽  
Douxing Li ◽  
Guanhu He ◽  
...  
Keyword(s):  
Carbon Steel ◽  
Current Density ◽  
High Current Density ◽  
Low Carbon Steel ◽  
Coarse Grained ◽  
High Current ◽  
Low Carbon ◽  
Crystalline Materials ◽  
Transmission Electron ◽  
Electropulsing Treatment

The microstructure of a low-carbon steel after high current density electropulsing treatment was characterized by high-resolution transmission electron microscopy. It was found that nanostructured γ-Fe could be formed in the coarse-grained steel after the electropulsing treatment. The mechanism of the formation of a nanostructure was discussed. It was thought that change of the thermodynamic barrier during phase transformation under electropulsing was a factor that cannot be neglected. It was reasonable to anticipate that a new method might be developed to produce nanostructured materials directly from the conventional coarse-grained crystalline materials by applying high current density electropulsing.

Microstructure Development in a High Current Density NbTi Superconducting Composite

1985 ◽  
Vol 43 ◽  
pp. 186-189
Author(s):  
P. J. Lee ◽  
D. C. Larbalestier
Keyword(s):  
Current Density ◽  
High Current Density ◽  
Cold Drawing ◽  
Heat Treatments ◽  
Grain Structure ◽  
Fine Grain ◽  
Boundary Film ◽  
Quantitative Basis ◽  
Cold Worked ◽  
Very High

Several features of the metallurgy of superconducting composites of Nb-Ti in a Cu matrix are of interest. The cold drawing strains are generally of order 8-10, producing a very fine grain structure of diameter 30-50 nm. Heat treatments of as little as 3 hours at 300 C (∼ 0.27 TM) produce a thin (1-3 nm) Ti-rich grain boundary film, the precipitate later growing out at triple points to 50-100 nm dia. Further plastic deformation of these larger a-Ti precipitates by strains of 3-4 produces an elongated ribbon morphology (of order 3 x 50 nm in transverse section) and it is the thickness and separation of these precipitates which are believed to control the superconducting properties. The present paper describes initial attempts to put our understanding of the metallurgy of these heavily cold-worked composites on a quantitative basis. The composite studied was fabricated in our own laboratory, using six intermediate heat treatments. This process enabled very high critical current density (Jc) values to be obtained. Samples were cut from the composite at many processing stages and a report of the structure of a number of these samples is made here.

Facet Topography and Dislocation Structure as a Possible Source for Electrical Heterogeneity in [001] TILT Bicrystals of YBa2Cu3O7-δ

1996 ◽  
Vol 54 ◽  
pp. 338-339
Author(s):  
I-Fei Tsu ◽  
D.L. Kaiser ◽  
S.E. Babcock
Keyword(s):  
Grain Boundary ◽  
Critical Current Density ◽  
Critical Current ◽  
Current Density ◽  
Electromagnetic Properties ◽  
Length Scale ◽  
Density Values ◽  
Current Densities ◽  
Applied Fields ◽  
A Current

A current theme in the study of the critical current density behavior of YBa2Cu3O7-δ (YBCO) grain boundaries is that their electromagnetic properties are heterogeneous on various length scales ranging from 10s of microns to ˜ 1 Å. Recently, combined electromagnetic and TEM studies on four flux-grown bicrystals have demonstrated a direct correlation between the length scale of the boundaries’ saw-tooth facet configurations and the apparent length scale of the electrical heterogeneity. In that work, enhanced critical current densities are observed at applied fields where the facet period is commensurate with the spacing of the Abrikosov flux vortices which must be pinned if higher critical current density values are recorded. To understand the microstructural origin of the flux pinning, the grain boundary topography and grain boundary dislocation (GBD) network structure of [001] tilt YBCO bicrystals were studied by TEM and HRTEM.

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