Nucleation and Growth of Grain Boundary Precipitates in Al-2.0 at.% Zn-1.0 at.% Mg Alloy at Elevated Temperatures / Keimung und Wachstum von Korngrenzenausscheidungen in einer Al-2,0 At.-% Zn-1,0 At.-% Mg-Legierung bei erhöhten Temperaturen

1988 ◽  
Vol 79 (5) ◽  
pp. 307-312
Author(s):  
Peter Czurratis ◽  
Rita Kroggel ◽  
Hans Löffler
Keyword(s):  
Grain Boundary ◽  
Elevated Temperatures ◽  
Nucleation And Growth ◽  
Mg Alloy

A Physically Based Constitutive Equation for Creep-Damaging Solids

1985 ◽  
Vol 52 (3) ◽  
pp. 615-620 ◽  
Author(s):  
A. J. Levy
Keyword(s):  
Constitutive Equation ◽  
Grain Boundary ◽  
Elevated Temperatures ◽  
Cavity Growth ◽  
Internal Variable ◽  
Nucleation And Growth ◽  
Creep Model ◽  
Steady Creep ◽  
Physically Based ◽  
Power Law Creep

Uniaxial and multiaxial forms of a constitutive equation, characterizing the creep-damaging behavior of metals at elevated temperatures, are developed based on Dyson’s constrained cavity growth mechanism. The model employs a single scalar internal variable which can be identified with the area fraction of cavitated boundaries. This variable, together with the power law creep model is capable of describing steady creep, tertiary creep, and dilatation arising from the nucleation and growth of grain boundary cavities.

Interface Structure and Slip Transmission in TI-49AL-3NB

1991 ◽  
Vol 229 ◽  
Author(s):  
Daniel S. Schwartz ◽  
S. M. L. Sastry
Keyword(s):  
Grain Boundary ◽  
Grain Boundaries ◽  
Interphase Boundary ◽  
Elevated Temperatures ◽  
Interface Structure ◽  
Nucleation And Growth ◽  
Slip Bands ◽  
Α Phase ◽  
Slip Transmission

AbstractTwo types of special grain boundaries were examined in Ti-49Al-3Nb deformed at elevated temperatures. The first can be described as a Σ=2 order-changing boundary. This boundary is faceted and results from the nucleation and growth of variants of the γ phase from the parent α phase. The second type of grain boundary is a γ/α2 interphase boundary, and transmission of slip through this type of boundary was examined. Slip transmission from γ into α2 did not produce distinct slip bands in α2,. Slip transmission from γ through α2, and into the next γ lamella was possible even when the next γ lamella was in an orientation rotated relative to the first γ lamella.

Structure of the grain boundary region in an Al–15 at.% Zn and Al–2.0 at.% Zn–1.3 at.% Mg alloy aged at elevated temperatures

1983 ◽  
Vol 18 (10) ◽  
pp. 1261-1276 ◽  
Author(s):  
V. Syneček ◽  
M. Simmerska ◽  
P. Bartuška ◽  
H. Löffler ◽  
R. Gerlach
Keyword(s):  
Grain Boundary ◽  
Elevated Temperatures ◽  
Boundary Region ◽  
Mg Alloy

Observations oh Nucleation and Growth of Voids in Nickel

1970 ◽  
Vol 28 ◽  
pp. 414-415
Author(s):  
J. L. Brimhall ◽  
H. E. Kissinger ◽  
B. Mastel
Keyword(s):  
High Purity ◽  
Growth Stage ◽  
Elevated Temperatures ◽  
Early Growth ◽  
Nucleation And Growth ◽  
Pure Nickel ◽  
Different Temperatures ◽  
Total Fluence ◽  
Neutron Exposure ◽  
Growth Of Voids

Some information on the size and density of voids that develop in several high purity metals and alloys during irradiation with neutrons at elevated temperatures has been reported as a function of irradiation parameters. An area of particular interest is the nucleation and early growth stage of voids. It is the purpose of this paper to describe the microstructure in high purity nickel after irradiation to a very low but constant neutron exposure at three different temperatures.Annealed specimens of 99-997% pure nickel in the form of foils 75μ thick were irradiated in a capsule to a total fluence of 2.2 × 1019 n/cm2 (E > 1.0 MeV). The capsule consisted of three temperature zones maintained by heaters and monitored by thermocouples at 350, 400, and 450°C, respectively. The temperature was automatically dropped to 60°C while the reactor was down.

Spherulite Structures in a Melt Spun Fe-Ni Austenitic Steel

1985 ◽  
Vol 43 ◽  
pp. 52-53
Author(s):  
G. M. Michal ◽  
T. K. Glasgow ◽  
T. J. Moore
Keyword(s):  
Austenitic Steel ◽  
Room Temperature ◽  
Elevated Temperatures ◽  
Large Range ◽  
Amorphous Structure ◽  
Nucleation And Growth ◽  
Ni Alloys ◽  
Melt Spun ◽  
Crystal Fibers ◽  
Rapidly Solidified

Large additions of B to Fe-Ni alloys can lead to the formation of an amorphous structure, if the alloy is rapidly cooled from the liquid state to room temperature. Isothermal aging of such structures at elevated temperatures causes crystallization to occur. Commonly such crystallization pro ceeds by the nucleation and growth of spherulites which are spherical crystalline bodies of radiating crystal fibers. Spherulite features were found in the present study in a rapidly solidified alloy that was fully crysstalline as-cast. This alloy was part of a program to develop an austenitic steel for elevated temperature applications by strengthening it with TiB2. The alloy contained a relatively large percentage of B, not to induce an amorphous structure, but only as a consequence of trying to obtain a large volume fracture of TiB2 in the completely processed alloy. The observation of spherulitic features in this alloy is described herein. Utilization of the large range of useful magnifications obtainable in a modern TEM, when a suitably thinned foil is available, was a key element in this analysis.

Inhomogeneous Swelling Near Grain Boundaries in Irradiated Materials: Cavity Nucleation and Growth Saturation Effects

2000 ◽  
Vol 650 ◽  
Author(s):  
S. L. Dudarev
Keyword(s):  
Grain Boundary ◽  
Grain Boundaries ◽  
Nucleation And Growth ◽  
Homogeneous Distribution ◽  
Rate Theory ◽  
Diffusional Growth ◽  
Standard Rate ◽  
Saturation Effects ◽  
Kinetics Of ◽  
Cascade Damage

ABSTRACTThe effect of inhomogeneous nucleation and growth of cavities near grain boundaries illustrates the failure of the standard rate theory to describe the kinetics of phase transformations in irradiated materials under cascade damage conditions. The enhanced swelling observed near grain boundaries is believed to result from the competition between the diffusional growth of cavities and their shrinkage due to the interaction with mobile interstitial clusters. Swelling rates associated with the two processes behave in a radically different way as a function of the size of growing cavities. For a spatially homogeneous distribution of cavities this gives rise to the saturation of swelling in the limit of large irradiation doses.We investigate the evolution of the population of cavities nucleating and growing near a planar grain boundary. We show that a cavity growing near the boundary is able to reach a size that is substantially larger than the size of a cavity growing in the interior region of the grain. For a planar grain boundary the magnitude of swelling at maximum is found to be up to eight times higher than the magnitude of swelling in the grain interior.

Microstructure Evolution and Mechanical Properties of an Al-Cu-Mg Alloy at Elevated Temperature

2014 ◽  
Vol 1004-1005 ◽  
pp. 148-153
Author(s):  
Min Hao ◽  
Ji Gang Ru ◽  
Ming Liu ◽  
Kun Zhang ◽  
Liang Wang ◽  
...  
Keyword(s):  
Electron Microscopy ◽  
Mechanical Properties ◽  
Elevated Temperature ◽  
Elevated Temperatures ◽  
Shear Fracture ◽  
S Phase ◽  
Mg Alloy ◽  
Transmission Electron ◽  
Fracture Features ◽  
Scanning Electron

Scanning electron microscopy (SEM) and transmission electron microscopy (TEM) were utilized to study the microstructure and mechanical behavior of an Al-Cu-Mg alloy after tensile test at 125°C, 150°C, 175°C and 200 °C, respectively. The yield strength and ultimate tensile strength decreased with the increase of temperature, while the elongation increased firstly and then decreased. The S and S′ precipitate after tension at elevated temperatures. When the temperature was higher than 175°C, the precipitate coarsens rapidly. The alloys displayed a shear fracture features at elevated temperature. The larger S′ and S phase coarsened and dropped which forming crack in the grain boundaries and precipitate interfaces, resulting in the decrease of the elongation of the alloy.

Significantly enhanced grain boundary Zn and Ca co-segregation of dilute Mg alloy via trace Sm addition

2021 ◽  
pp. 142259
Author(s):  
Zhi Zhang ◽  
Jinghuai Zhang ◽  
Jinshu Xie ◽  
Shujuan Liu ◽  
Yuying He ◽  
...  
Keyword(s):  
Grain Boundary ◽  
Mg Alloy

Improvement of Superplasticity in Fine-Grained Oxide Ceramics Based on the Concept of Grain Boundary Plasticity

2016 ◽  
Vol 838-839 ◽  
pp. 34-40
Author(s):  
Hidehiro Yoshida ◽  
Koji Morita ◽  
Byung Nam Kim ◽  
Koji Matsui ◽  
Yuichi Ikuhara ◽  
...  
Keyword(s):  
Grain Boundary ◽  
Atomic Structure ◽  
Nucleation And Growth ◽  
Phenomenological Analysis ◽  
Research Field ◽  
Oxide Ceramics ◽  
Cavity Nucleation ◽  
Fine Grained ◽  
Experimental Strain ◽  
New Research

Superplasticity in fine-grained oxide ceramics has been generally elucidated on the basis of their experimental strain rate-flow stress relationship and phenomenological analysis of cavity nucleation and growth. It has been widely accepted that the high temperature superplastic flow and failure in ceramics is significantly influenced by the atomic structure and chemistry of grain boundaries. Such phenomenon cannot be explained based on the classical phenomenological analysis. Our research group has therefore proposed to establish a new research field, grain boundary plasticity, to describe the superplastic deformation related to the grain boundary atomic structure. This paper aims to point out the importance of the atomistic analysis of grain boundary to develop new superplastic ceramics.

Sign in / Sign up

Export Citation Format

Share Document