On the Diffusivity of Au in Pb

1985 ◽  
Vol 57 ◽  
Author(s):  
Ann N. Campbell ◽  
David Turnbull
Keyword(s):  
High Temperature ◽  
Grain Boundary ◽  
Ostwald Ripening ◽  
Second Phase ◽  
Precipitate Phase ◽  
Tracer Diffusivity ◽  
Interstitial Defect ◽  
The Matrix ◽  
Kinetics Of ◽  
Good Agreement

AbstractThe precipitation of Pb3Au from dilute Pb(Au) alloys and the subsequent Ostwald ripening of the precipitate phase have been studied. The Au diffusivity which limits the precipitation from Pb(500 at. ppm Au) specimens is in good agreement with Dp = 45 exp[(−20.8 kcal/mol)/RT], found previously to control the precipitation rate in Pb(900–1000 at. ppm Au) alloys (Rossolimo and Turnbull, 1973). In contrast, precipitation from Pb(100 at. ppm Au) alloys and Ostwald ripening in the Pb(500 at. ppm Au) specimens appear to be governed by the high temperature Au tracer diffusivity, DAu = 0.0041 exp[(−9.35 kcal/mol)/RT], which is about 103 times greater than Dp at the temperatures of interest, 75 to 112°C, and is attributed to the motion of a Au interstitial defect. In the 100 ppm alloys the Au is incorporated most easily at the ends of the Pb3Au crystals and a ribbon- or whisker-like morphology results. The particles which form at the grain boundaries in the 500 ppm Au alloy specimens are at least six times larger in volume than the matrix particles and ripen at their expense. The Ostwald ripening kinetics of the grain boundary particles scale with t1/2 rather than with t1/3 as is usual. The Pb3Au formed whiskers, blades, ribbons, or equiaxed particles depending upon the Au concentration and precipitation temperature. The precipitation and ripening kinetics are critically dependent on the morphology of the second phase.

The Effect of Grain-Boundary and Matrix Precipitates on High Temperature Strength in Fe3Al Based Alloys

2011 ◽  
Vol 1295 ◽  
Author(s):  
Ryo Makihara ◽  
Satoru Kobayashi ◽  
Takayuki Takasugi
Keyword(s):  
High Temperature ◽  
Grain Boundary ◽  
Tensile Tests ◽  
High Temperature Strength ◽  
Second Phase ◽  
Proof Stress ◽  
Second Phase Particles ◽  
The Matrix

ABSTRACTThe effect of grain boundary (GB) and matrix precipitates on high temperature strength was investigated in Fe3Al base alloys containing Cr, Mo and C. Tensile tests were conducted at 600°C for three types of microstructures consisting of: (I) film-like κ phase precipitates covering GBs and fine M2C particles in the matrix, (II) only fine M2C particles in the matrix and (III) no second-phase particles in the matrix. It was found that κ films on GBs are more than twice as effective as finely dispersed M2C particles for improving the proof stress.

scholarly journals Microstructure and Tensile Properties of Graphene-Oxide-Reinforced High-Temperature Titanium-Alloy-Matrix Composites

Materials ◽  
2020 ◽  
Vol 13 (15) ◽  
pp. 3358 ◽  
Author(s):  
Hang Chen ◽  
Guangbao Mi ◽  
Peijie Li ◽  
Xu Huang ◽  
Chunxiao Cao
Keyword(s):  
Tensile Strength ◽  
Titanium Alloy ◽  
Graphene Oxide ◽  
High Temperature ◽  
Yield Strength ◽  
Room Temperature ◽  
Second Phase ◽  
Matrix Composites ◽  
Alloy Matrix ◽  
The Matrix

In this study, graphene-oxide (GO)-reinforced Ti–Al–Sn–Zr–Mo–Nb–Si high-temperature titanium-alloy-matrix composites were fabricated by powder metallurgy. The mixed powders with well-dispersed GO sheets were obtained by temperature-controlled solution mixing, in which GO sheets adsorb on the surface of titanium alloy particles. Vacuum deoxygenating was applied to remove the oxygen-containing groups in GO, in order to reduce the introduction of oxygen. The compact composites with refined equiaxed and lamellar α phase structures were prepared by hot isostatic pressing (HIP). The results show that in-situ TiC layers form on the surface of GO and GO promotes the precipitation of hexagonal (TiZr)6Si3 particles. The composites exhibit significant improvement in strength and microhardness. The room-temperature tensile strength, yield strength and microhardness of the composite added with 0.3 wt% GO are 9%, 15% and 27% higher than the matrix titanium alloy without GO, respectively, and the tensile strength and yield strength at 600 °C are 3% and 21% higher than the matrix alloy. The quantitative analysis indicates that the main strengthening mechanisms are load transfer strengthening, grain refinement and (TiZr)6Si3 second phase strengthening, which accounted for 48%, 30% and 16% of the improvement of room-temperature yield strength, respectively.

Deformation Induced Phase Seperation of Ni45Co5 Mn36.7In13.3 Alloy at High Temperature

2011 ◽  
Vol 702-703 ◽  
pp. 896-899
Author(s):  
Gang Wang ◽  
Chun Yan Wang ◽  
Zhe Chen ◽  
Wen Ru Zhao ◽  
Yan Dong Liu ◽  
...  
Keyword(s):  
High Temperature ◽  
Hot Deformation ◽  
Matrix Alloy ◽  
Second Phase ◽  
Magnetic Shape Memory ◽  
Magnetic Shape Memory Alloys ◽  
The Matrix ◽  
New Type ◽  
Materials Used ◽  
Fcc Structure

NiMnCoIn alloys are new-type magnetic shape memory alloys (MSMAs) in which a reversible magnetic-field-induced phase transformation was observed. They are ideal candidates of materials used in actuators and sensors. The polycrystalline NiMnCoIn alloys are generally brittle so that they can not be easily deformed into the shape applicable to actuators and sensors until now. In the present paper, the influence of hot deformation on the microstructure of Ni45Co5Mn36.7In13.3alloy was studied. The experimental results showed that second phase was observed after deformation at high temperature between 800~900 °C and at strain rate lower than 4×10-3s-1. The content of Co of second phase was higher than the matrix alloy, while the content of In was lower than the matrix alloy. It was determined by TEM measurements as γ phase with fcc structure which was popular in NiFeGa and NiMnGaCo alloys. It is possible to improve the ductility of Ni45Co5Mn36.7In13.3alloy by control of amount and distribution of γ phase by hot deformation.

Study on Creep Properties of SiCp/AZ61 Composites

2011 ◽  
Vol 189-193 ◽  
pp. 4227-4230
Author(s):  
Hong Yan ◽  
Zhi Min Huang
Keyword(s):  
Thermal Analysis ◽  
High Temperature ◽  
Grain Boundary ◽  
Grain Boundaries ◽  
Dynamic Mechanical Thermal Analysis ◽  
Creep Properties ◽  
Casting Technique ◽  
Sic Particles ◽  
The Matrix ◽  
Semi Solid

SiCp/AZ61 composites reinforced with SiC particles were fabricated by semi-solid stirring-melt casting technique. The creep properties of the composites have been studied by dynamic mechanical thermal analysis, micro-structural and XRD observation. The results show that the matrix grains were refined obviously at high temperature with SiC particles introducing and the creep properties of SiCp/AZ61 composites were improved comparing with AZ61 alloy. SiC particles were substituted for Mg17Al12 phase that was easily intenerated at high temperature on grain boundaries. The pinning of SiC particles prevents dislocation and slip of grain boundary at high temperature.

GLIDCOP AL-60

Alloy Digest ◽  
1996 ◽  
Vol 45 (8) ◽  
Keyword(s):  
Thermal Conductivity ◽  
High Temperature ◽  
Aluminum Oxide ◽  
Creep Resistance ◽  
High Strength ◽  
Thermal Softening ◽  
Second Phase ◽  
Temperature Performance ◽  
The Matrix ◽  
Metal Products

Abstract GlidCop AL-60 is copper strengthened by adding a second phase (aluminum oxide) to the matrix by internal oxidation. The process produces a product with resistance to thermal softening, high strength, and creep resistance, combined with high electrical and thermal conductivity. (See also GlidCop AL-15, Alloy Digest Cu-603, May 1996, and GlidCop AL-25, Alloy Digest Cu-604, June 1996.) This datasheet provides information on composition, physical properties, hardness, elasticity, and tensile properties. It also includes information on high temperature performance as well as forming and joining. Filing Code: CU-608. Producer or source: SCM Metal Products Inc.

GLIDCOP AL-15

Alloy Digest ◽  
1996 ◽  
Vol 45 (5) ◽  
Keyword(s):  
Thermal Conductivity ◽  
High Temperature ◽  
Aluminum Oxide ◽  
Physical Properties ◽  
High Strength ◽  
Thermal Softening ◽  
Second Phase ◽  
Temperature Performance ◽  
The Matrix ◽  
Metal Products

Abstract GlidCop AL-15 is copper strengthened by adding a second phase, aluminum oxide, to the matrix by internal oxidation. The process produces a product with resistance to thermal softening, high strength, and creep, combined with high electrical and thermal conductivity. (See also GlidCop AL-25, Alloy Digest Cu-604, June 1996, and GlidCop AL-60, Alloy Digest Cu-608, August 1996.) This datasheet provides information on composition, physical properties, hardness, elasticity, and tensile properties as well as creep. It also includes information on high temperature performance as well as forming and joining. Filing Code: CU-603. Producer or source: SCM Metal Products Inc.

Impression Creep Behavior of Atmospheric Plasma-Sprayed and Hot Pressed MoSi2/Si3N4

1997 ◽  
Author(s):  
K.J. Hollis ◽  
D.P. Butt ◽  
R.G. Castro
Keyword(s):  
High Temperature ◽  
Grain Boundary ◽  
Creep Behavior ◽  
Grain Boundary Sliding ◽  
Atmospheric Plasma ◽  
Second Phase ◽  
Impression Creep ◽  
Creep Mechanisms ◽  
Boundary Sliding ◽  
Plasma Sprayed

Abstract The use of MoSi2 as a high temperature oxidation resistant structural material is hindered by its poor elevated temperature creep resistance. The addition of second phase Si3N4 holds promise for improving the creep properties of MoSi2 without decreasing oxidation resistance. The high temperature impression creep behavior of atmospheric plasma sprayed (APS) and hot pressed (HP) MoSi2/Si3N4 composites was investigated. Values for steady state creep rates, creep activation energies, and creep stress exponents were measured. Grain boundary sliding and splat sliding were found to be the dominant creep mechanisms for the APS samples while grain boundary sliding and plastic deformation were found to be the dominant creep mechanisms for the HP samples.

scholarly journals Precipitation and Growth Kinetics in Mechanically Alloyed Ni–Al

2011 ◽  
Vol 2011 ◽  
pp. 1-7 ◽  
Author(s):  
QingXin Tang ◽  
Shigeharu Ukai ◽  
Akinobu Minami ◽  
Shigenari Hayashi
Keyword(s):  
Growth Kinetics ◽  
Ostwald Ripening ◽  
Arrhenius Plot ◽  
Lattice Misfit ◽  
Oxide Dispersion Strengthened ◽  
Mechanically Alloyed ◽  
Spherical Type ◽  
Atom Diffusion ◽  
The Matrix ◽  
Kinetics Of

The precipitation and growth kinetics ofγ′ precipitates, which are strengthening factors in Ni-base oxide dispersion strengthened (ODS) superalloys, were investigated. The cuboidal-typeγ′ precipitates are formed in conventional arc-melted Ni–Al alloys, whereas spherical-type precipitates are formed in the mechanically alloyed (MAed) specimens. The morphology is controlled by a lattice misfit between theγ′ precipitates and the matrix at the aging temperature of 800°C. The growth kinetics of theγ′ precipitates can be followed by Ostwald ripening. The Arrhenius plot yielded a lower activation energy for the solute atom diffusion in MAed specimens, which is attributed to their high dislocation density and nanosized grains.

On the theory of the effect of precipitate particles on grain growth in metals

1966 ◽  
Vol 294 (1438) ◽  
pp. 298-309 ◽  
Keyword(s):  
Particle Size ◽  
Grain Size ◽  
Grain Boundary ◽  
Grain Growth ◽  
Boundary Energy ◽  
Second Phase ◽  
Pinning Force ◽  
Essential Difference ◽  
The Matrix ◽  
Critical Particle Size

A theoretical model of the energy changes accompanying grain boundary movement has been developed. It has been shown that small boundary movements will reduce the energy of a polycrystalline metal only when there is a heterogeneous grain size. The pinning force exerted by precipitate particles of a second phase on the grain boundary has also been considered. The release of grain boundary energy which accompanies grain growth has been considered as a source of energy for the unpinning process. The theory predicts a critical particle size which is dependent on the volume fraction of second phase, the matrix grain size, and the degree of heterogeneity of the matrix. Coalescence of the precipitate to a size in excess of the critical radius will permit grain growth to occur. Theoretical predictions of the critical particle size are in good agreement with values determined experimentally. The essential difference between grain growth and secondary recrystallization is indicated by the theory.

Thermal Degradation Characteristics and Kinetics of High Temperature Vulcanized (HTV) Silicone Rubber/POSS Hybrid

2011 ◽  
Vol 105-107 ◽  
pp. 1657-1661 ◽  
Author(s):  
Dong Yang ◽  
Wei Zhang ◽  
Ru Liang Yao ◽  
Ben Zheng Jiang
Keyword(s):  
High Temperature ◽  
Thermal Degradation ◽  
Silicone Rubber ◽  
Degradation Kinetics ◽  
Three Dimensional ◽  
Mean Value ◽  
Silicon Rubber ◽  
The Matrix ◽  
Oligomeric Silsesquioxane ◽  
Kinetics Of

A high temperature vulcanized (HTV) silicone rubber/octavinyl polyhedral oligomeric silsesquioxane (POSS) hybrid was prepared. The micromorphology of the cured hybrid was investigated by scanning electron microscopy (SEM); the thermal degradation stability of this hybrid was studied by means of thermal gravimetric analyses (TGA); the degradation kinetics of this hybrid was also studied using Doyle method and Coats-Redfern method. Results showed that aggregation of self-cross-linked octavinyl POSS appeared in the HTV silicon rubber/POSS hybrid. The incorporation of POSS into silicon rubber networks enhanced the thermal degradation resistance of the matrix. Activation energy derived by the Coats-Redfern method (142.24 kJ/mol) showed a good agreement with the mean value derived by the Doyle method (146.51 kJ/mol); the thermal degradation reaction of the hybrid followed a three-dimensional diffusion law (D4).

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