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.

Crack Deflection and Interfacial Fracture Energies in Alumina/SiC and Alumina/TiN Nanocomposites

1996 ◽  
Vol 457 ◽  
Author(s):  
S. Jiao ◽  
M. L. Jenkins
Keyword(s):  
Grain Boundary ◽  
Crack Propagation ◽  
Grain Boundaries ◽  
Interfacial Fracture ◽  
Crack Deflection ◽  
Dihedral Angles ◽  
Particle Interactions ◽  
Interfacial Energies ◽  
Sic Particles ◽  
The Matrix

ABSTRACTCrack/particle interactions in Al2O3/SiC and Al2O3/TiN nanocomposites have been observed by TEM on samples containing cracks produced by Vickers indentations. No significant crack deflection by intragranular SiC particles or microcracking around nanoparticles was found. Intergranular cracks were observed to be deflected into the matrix grains by SiC particles on grain boundaries inclined to the direction of crack propagation. TiN particles were not effective in this way. These features are briefly discussed within the framework of the interfacial fracture energies. These were calculated from interfacial energies, which were determined by the measurement of grain boundary-interface dihedral angles.

scholarly journals Recrystallization processes, microstructure and crystallographic preferred orientation evolution in polycrystalline ice during high-temperature simple shear

2019 ◽  
Vol 13 (5) ◽  
pp. 1495-1511 ◽  
Author(s):  
Baptiste Journaux ◽  
Thomas Chauve ◽  
Maurine Montagnat ◽  
Andrea Tommasi ◽  
Fabrice Barou ◽  
...  
Keyword(s):  
High Temperature ◽  
Grain Boundary ◽  
Dynamic Recrystallization ◽  
Grain Boundaries ◽  
Simple Shear ◽  
Shear Plane ◽  
Preferred Orientation ◽  
Dislocation Slip ◽  
Crystallographic Preferred Orientation ◽  
Polycrystalline Ice

Abstract. Torsion experiments were performed in polycrystalline ice at high temperature (0.97 Tm) to reproduce the simple shear kinematics that are believed to dominate in ice streams and at the base of fast-flowing glaciers. As clearly documented more than 30 years ago, under simple shear ice develops a two-maxima c axis crystallographic preferred orientation (CPO), which evolves rapidly into a single cluster CPO with a c axis perpendicular to the shear plane. Dynamic recrystallization mechanisms that occur in both laboratory conditions and naturally deformed ice are likely candidates to explain the observed CPO evolution. In this study, we use electron backscatter diffraction (EBSD) and automatic ice texture analyzer (AITA) to characterize the mechanisms accommodating deformation, the stress and strain heterogeneities that form under torsion of an initially isotropic polycrystalline ice sample at high temperature, and the role of dynamic recrystallization in accommodating these heterogeneities. These analyses highlight an interlocking microstructure, which results from heterogeneity-driven serrated grain boundary migration, and sub-grain boundaries composed of dislocations with a [c]-component Burgers vector, indicating that strong local stress heterogeneity develops, in particular, close to grain boundaries, even at high temperature and high finite shear strain. Based on these observations, we propose that nucleation by bulging, assisted by sub-grain boundary formation and followed by grain growth, is a very likely candidate to explain the progressive disappearance of the c axis CPO cluster at low angle to the shear plane and the stability of the one normal to it. We therefore strongly support the development of new polycrystal plasticity models limiting dislocation slip on non-basal slip systems and allowing for efficient accommodation of strain incompatibilities by an association of bulging and formation of sub-grain boundaries with a significant [c] component.

Advantages of MIS Processing on Passivated Polycrystalline Silicon

1981 ◽  
Vol 5 ◽  
Author(s):  
G. Rajeswaran ◽  
M. Thayer ◽  
V. J. Rao ◽  
W. A. Anderson
Keyword(s):  
High Temperature ◽  
Low Temperature ◽  
Grain Boundary ◽  
Grain Boundaries ◽  
Polycrystalline Silicon ◽  
Hydrogen Plasma ◽  
Mis Structures

ABSTRACTWacker polycrystalline silicon shows enhanced grain boundary activity after a high temperature (950° C) anneal. It is possible to passivate this effect in a hydrogen plasma. The low temperature (600° C) processing of MIS technology does not activate grain boundaries or deteriorate a passivated specimen. Activated grain boundaries with MIS structures can be used to assess the character of recombination currents. It is concluded that MIS processing is advantageous for passivated polycrystalline silicon.

scholarly journals Effect of Grain Boundary Precipitates on High Temperature Creep Properties of Ni-2OCr-Nb-W Alloys

1986 ◽  
Vol 72 (10) ◽  
pp. 1605-1612 ◽  
Author(s):  
Masao TAKEYAMA ◽  
Kaoru KAWASAKI ◽  
Takashi MATSUO ◽  
Ryohei TANAKA
Keyword(s):  
High Temperature ◽  
Grain Boundary ◽  
High Temperature Creep ◽  
Creep Properties ◽  
Temperature Creep

The role of microscopy in the alloy design of Ni- and Fe-based aluminides

1992 ◽  
Vol 50 (1) ◽  
pp. 168-169
Author(s):  
J.A. Horton
Keyword(s):  
High Temperature ◽  
Grain Boundary ◽  
Grain Boundaries ◽  
Oxidation Resistance ◽  
Industrial Applications ◽  
Al Alloys ◽  
Ordered Alloys ◽  
Successful Control ◽  
Oxidation Resistant

During the last 10 years, there has been a resurgence of interest in ordered alloys for structural uses due to the discovery of the dramatic ductilizing effect of boron on grain boundaries in Ni3Al. With this discovery, it was hoped that the property of an increase in strength as the temperature is increased could be utilized as well as the excellent oxidation resistance. Now, alloys based on Ni3Al are in use in specialized industrial applications, such as high temperature forging dies and being tested for use as turbocharger rotors. Due to the successful control of the grain boundary strength in Ni3Al, other systems were reexamined. For example, Fe3Al was also thought to have inherently brittle grain boundaries, however it was found that with purer alloys the material failed by cleavage. Subsequently, development of practical, inexpensive, oxidation resistant alloys has proceeded. Fe3Al alloys are currently being tested for automobile exhaust applications.

Grain boundary composition in silicon nitride

1987 ◽  
Vol 45 ◽  
pp. 162-163
Author(s):  
S. A. Bradley ◽  
K. R. Karasek
Keyword(s):  
Electron Microscopy ◽  
Silicon Nitride ◽  
Grain Boundary ◽  
Grain Boundaries ◽  
Analytical Electron Microscopy ◽  
High Resolution Electron Microscopy ◽  
Scanning Transmission Electron Microscope ◽  
Creep Properties ◽  
Second Phases ◽  
Major Factors

Since one of the major factors for controlling creep properties in silicon nitride components is the addition of sintering aids, determination of the composition of the resulting intergranular second phases becomes very important. High resolution electron microscopy has been used to investigate the crystalline or non-crystalline character of the grain boundary while analytical electron microscopy studies have focused on the composition of the grain boundary pockets. As sintering aid additions and processing become more complex, multiple second phases are produced. Ascertaining the composition of the grain boundaries and grain boundary pockets is necessary for correlating the microstructure with the creep properties.A dedicated VG HB-5 scanning transmission electron microscope was used to measure the composition of grain boundaries and grain boundary pockets of silicon nitride.

On the Relationship Between Grain-Boundary Character Distribution and Intergranular Corrosion

1996 ◽  
Vol 54 ◽  
pp. 346-347
Author(s):  
E.M. Lehockey ◽  
G. Palumbo ◽  
P. Lin ◽  
A. Brennenstuhl
Keyword(s):  
Grain Boundaries ◽  
Intergranular Corrosion ◽  
Grain Boundary Character Distribution ◽  
Hexagonal Prism ◽  
Material Loss ◽  
Creep Properties ◽  
Special Boundaries ◽  
Grain Boundary Character ◽  
The Matrix ◽  
The Relationship

Intergranular corrosion can under severe conditions lead to “grain-dropping” which results in significant material loss. It has been demonstrated that grain boundaries described by low-Σ CSL misorientations are more resistant to corrosion, cracking (SCC), and sliding (creep) than “general” boundaries, and that the frequency of these “special” boundaries can be enhanced offering the possibility of producing materials with improved bulk corrosion and creep properties. This contribution presents a model for predicting the effect of “special” boundaries on the extent of gross wastage from grain-dropping.For any grain to be ejected from the matrix, all of its bounding interfaces must be fully compromised. Assuming “special” grain boundaries are immune to corrosion and considering a material containing hexagonal prism grains with a diameter and length, d, it can be shown that the probability, X, of observing grain-dropping at a depth, L, through the material thickness is related to the “special” boundary fraction, Fsp, by:

Effect of niobium and austenitizing temperature on the microstructures and properties of spray-deposited AISI M3:2 high speed steel

2021 ◽  
Vol 119 (1) ◽  
pp. 102
Author(s):  
Hebin Wang ◽  
Da Hong ◽  
Longgang Hou ◽  
Li Shen ◽  
Ping Ou ◽  
...  
Keyword(s):  
High Temperature ◽  
Grain Boundaries ◽  
High Speed ◽  
High Speed Steel ◽  
High Hardness ◽  
Spray Forming ◽  
Precipitation Strengthening ◽  
Austenitizing Temperature ◽  
The Matrix ◽  
Red Hardness

The microstructure and properties of niobium-containing AISI M3:2 high speed steels (HSSs) fabricated by spray forming and traditional casting have been investigated. The results show that fine and uniformly-distributed grains without macrosegregation appeared in the as-deposited HSSs that differ from those of as-cast HSSs. Nb mostly appears in primary MC carbides, whereas it contributes less to the formation of M6C carbides. The high stabilization of Nb-rich MC carbides can pin the grain boundaries during high-temperature austenitizing process, thus conferring a fine grains and raising the content of dissolved alloying elements. Enhanced precipitation strengthening and fine dispersion of NbC carbides throughout the matrix contribute to the high hardness and red hardness of Nb-containing HSS.

Microstructural Evolution and Precipitation Mechanism of α-Phase in Ti-55531 Alloy Aged at High Temperature

2013 ◽  
Vol 747-748 ◽  
pp. 912-918 ◽  
Author(s):  
Xue Zhang ◽  
Yi Chen ◽  
Feng Shou Zhang ◽  
Jun Ting Yang ◽  
Yun Jin Lai ◽  
...  
Keyword(s):  
High Temperature ◽  
Grain Boundary ◽  
Grain Boundaries ◽  
Microstructural Evolution ◽  
Boundary Energy ◽  
High Energy ◽  
Ageing Temperature ◽  
Α Phase ◽  
Temperature Ageing ◽  
Annealing Heat Treatment

After two-stage annealing heat treatment process, the near β-Titanium alloys reveal a mixed microstructure containing lath-like α phase and finer acicular α phase in β matrix, leading to the improvement of strength-ductility balance. In this paper, the microstructural evolution and the behaviour of α precipitate during high temperature ageing process were investigated by SEM in a near β-Titanium alloy called Ti-55531.The relationship between α precipitates and the β grain orientation in high temperature was investigated by EBSD. The results show that the α-phase precipitated only at some places of the β grain boundaries at higher ageing temperature (~780 °C); the amount of grain boundary α increased with the decreased of the ageing temperature; after ageing at 720 °C for 45 min, we found that the α-phase precipitated not only at grain boundaries but also within the grains. It seems that the precipitation of grain boundary α is strongly influenced by β grain boundary energy which means that grain boundary α tends to form preferentially at high energy grain boundaries (high-angle grain boundaries); The α-phase precipitates more easily at the grain boundaries where the {110} plane of adjacent β grains have the same orientation.

Localized Deformation Induced IGSCC and IASCC of Austenitic Alloys in High Temperature Water

2004 ◽  
Vol 261-263 ◽  
pp. 885-902 ◽  
Author(s):  
G.S. Was ◽  
B. Alexandreanu ◽  
J. Busby
Keyword(s):  
High Temperature ◽  
Grain Boundary ◽  
Grain Boundaries ◽  
Stress Corrosion ◽  
Stress Corrosion Cracking ◽  
Corrosion Cracking ◽  
Localized Deformation ◽  
High Temperature Water ◽  
Austenitic Alloys ◽  
Temperature Water

Grain boundary properties are known to affect the intergranular stress corrosion cracking (IGSCC) and irradiation assisted stress corrosion cracking behavior of austenitic alloys in high temperature water. However, it is only recently that sufficient evidence has accumulated to show that the disposition of deformation in and near the grain boundary plays a key role in intergranular cracking. Grain boundaries that can transmit strain to adjacent grains can relieve stresses without undergoing localized deformation. Grain boundaries that cannot transmit strain will either experience high stresses or high strains. High stresses can lead to wedge-type cracking and sliding can lead to rupture of the protective oxide film. These processes are also applicable to irradiated materials in which the deformation can become highly localized in the form of dislocation channels and deformation twins. These deformation bands conduct tremendous amounts of strain to the grain boundaries. The capability of a boundary to transmit strain to a neighboring grain will determine its propensity for cracking, analogous to that in unirradiated metals. Thus, IGSCC in unirradiated materials and IASCC in irradiated materials are governed by the same local processes of stress and strain accommodation at the boundary.

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