Modeling Interparticle Size Effect on Deformation Behavior of Metal Matrix Composites by a Gradient Enhanced Plasticity Model

2011 ◽  
Vol 133 (4) ◽  
Author(s):  
Rashid K. Abu Al-Rub ◽  
Mahmood Ettehad
Keyword(s):  
Particle Size ◽  
Plastic Strain ◽  
Size Effect ◽  
Metal Matrix ◽  
Mechanical Response ◽  
Volume Fraction ◽  
Experimental Tests ◽  
Interparticle Spacing ◽  
Precipitate Size ◽  
Aspect Ratios

Experimental tests show that particle (inclusion or precipitate) size and interparticle spacing, besides volume fraction, have a considerable effect on the macroscopic mechanical response of metal matrix microreinforced composites. Classical (local) plasticity models unlike nonlocal gradient enhanced plasticity models cannot capture this size dependency due to the absence of a material length scale. In this paper, one form of higher-order gradient plasticity enhanced model, which is derived based on principle of virtual power and laws of thermodynamic, is employed to investigate the size effect of elliptical inclusions with different aspect ratios based on unit cell simulations. It is shown that by decreasing the particle size or equivalently the interparticle spacing (i.e., the spacing between the centers of inclusions), while keeping the volume fraction constant, the average stress–strain response is stronger and more sensitive to the inclusion’s aspect ratio. However, unexpectedly, decreasing the free-path interparticle spacing (i.e., the spacing between the edges of inclusions perpendicular to the principal loading direction) does not necessarily lead to largest strengthening. This is completely dependent on the plastic strain gradient hardening due to distribution and evolution of geometrically necessary dislocations that depend on the particle size and shape. Gradient-hardening significantly alter the stress and plastic strain distributions near the particle-matrix interface.

Climb-Enabled Discrete Dislocation Plasticity Analysis of the Deformation of a Particle Reinforced Composite

2015 ◽  
Vol 82 (7) ◽  
Author(s):  
C. Ayas ◽  
L. C. P. Dautzenberg ◽  
M. G. D. Geers ◽  
V. S. Deshpande
Keyword(s):  
Particle Size ◽  
Size Effect ◽  
Strain Hardening ◽  
Volume Fraction ◽  
Dislocation Motion ◽  
Dislocation Climb ◽  
Discrete Dislocation ◽  
Dislocation Plasticity ◽  
Wall Structures ◽  
The Matrix

The shear deformation of a composite comprising elastic particles in a single crystal elastic–plastic matrix is analyzed using a discrete dislocation plasticity (DDP) framework wherein dislocation motion occurs via climb-assisted glide. The topology of the reinforcement is such that dislocations cannot continuously transverse the matrix by glide-only without encountering the particles that are impenetrable to dislocations. When dislocation motion is via glide-only, the shear stress versus strain response is strongly strain hardening with the hardening rate increasing with decreasing particle size for a fixed volume fraction of particles. This is due to the formation of dislocation pile-ups at the particle/matrix interfaces. The back stresses associated with these pile-ups result in a size effect and a strong Bauschinger effect. By contrast, when dislocation climb is permitted, the dislocation pile-ups break up by forming lower energy dislocation wall structures at the particle/matrix interfaces. This results in a significantly reduced size effect and reduced strain hardening. In fact, with increasing climb mobility an “inverse size” effect is also predicted where the strength decreases with decreasing particle size. Mass transport along the matrix/particle interface by dislocation climb causes this change in the response and also results in a reduction in the lattice rotations and density of geometrically necessary dislocations (GNDs) compared to the case where dislocation motion is by glide-only.

Formation of Cavities From Nondeformable Second-Phase Particles in Low Temperature Ductile Fracture

1976 ◽  
Vol 98 (1) ◽  
pp. 60-68 ◽  
Author(s):  
A. S. Argon
Keyword(s):  
Particle Size ◽  
Stress Concentration ◽  
Size Effect ◽  
Volume Fraction ◽  
Void Formation ◽  
Particle Size Effect ◽  
Interfacial Stress ◽  
Second Phase ◽  
Rigid Particles ◽  
The Matrix

Limiting solutions are discussed for elastic-plastic deformation around rigid particles of both equiaxed and greatly elongated shapes. It is shown that if the matrix can be characterized as a rigid nonhardening continuum the stress concentration at the particle interface and interior is less than two for either equiaxed or elongated particles. In a rapidly strain hardening matrix, however, while the interfacial stress concentration relative to the distant boundary traction remains at a factor of two for the equiaxed particles, it rises nearly linearly with aspect ratio for slender platelets and rods. Interaction between particles can occur when the local volume fraction of particles is high. Such interactions raise the interface tractions for a given state of shear of the matrix and hasten void formation, and are often discerned as a particle size effect. Another particle size effect based on flawed particles is also discussed.

scholarly journals A New Model for Predicting Low Cycle Fatigue Behavior of Discontinuously Reinforced Metal Matrix Composites

2021 ◽  
Author(s):  
Qian Zhang
Keyword(s):  
Particle Size ◽  
Crack Initiation ◽  
Metal Matrix Composites ◽  
Metal Matrix ◽  
Volume Fraction ◽  
Low Cycle Fatigue ◽  
Fatigue Behavior ◽  
Plastic Strain Amplitude ◽  
Strain Hardening Exponent ◽  
Matrix Composites

An analytical model for predicitng the crack inititation life of low cycle fatique (LCF) of discontinuously reinforced metal matrix composites (DR-MMCs) has been proposed. The effects of the volume fraction Vf cyclic strain hardening exponent n' and cyclic strength coefficient K' on the LCF crack initiation life of DR-MMCs were analyzed. While both the lower level of the plastic strain amplitude and the lower Vf were found to increase the LCF crack initiation resistance, the effects of n' and K' were more complicated. By considering the enhanced dislocation density in the matrix and the load bearing effect of particles, a quantitative relationship between the LCF life of DR-MMCs and particle size was also derived. This model showed that a decreasing particle size results in a longer LCF life. The theoretical predictions based on the proposed models were found to be in good agreement with the experimental data reported in the literature.

Excessive ThO2 Particle Growth in Ni-2ThO2 at High Temperature

1970 ◽  
Vol 28 ◽  
pp. 416-417
Author(s):  
E. R. Kimmel ◽  
H. L. Anthony ◽  
W. Scheithauer
Keyword(s):  
Particle Size ◽  
Metal Matrix ◽  
Oxide Dispersion Strengthened ◽  
Particle Growth ◽  
Interparticle Spacing ◽  
Refractory Oxide ◽  
Oxide Dispersion ◽  
Volume Percent ◽  
Oxide Particles ◽  
Cold Worked

It is generally accepted that a uniform spatial distribution of fine refractory oxide particles is required in an oxide-dispersion-strengthened metal to provide good elevated-temperature strengths. The presence of these particles stabilizes the cold-worked microstructure by anchoring low-angle cell boundaries and by restricting the motion of dislocations during loading. Such action by the particles must be a function of the interparticle spacing as is proposed by the Orowan model for yield stress. For a given volume percent of oxide in the metal matrix, the interparticle spacing is directly proportional to the particle size. Therefore, particle growth during the processing of oxide-dispersion-strengthened metals increases the interparticle spacing and inherently decreases the strength.

Effects of Particle Size and Volume Fraction on Extrusion Texture of SiCp/Al Metal Matrix Composites

2011 ◽  
Vol 194-196 ◽  
pp. 1437-1441 ◽  
Author(s):  
Chun Lin He ◽  
Jian Ming Wang ◽  
Qing Kui Cai
Keyword(s):  
Particle Size ◽  
Metal Matrix Composites ◽  
Metal Matrix ◽  
Volume Fraction ◽  
Deformation Texture ◽  
Fiber Texture ◽  
Matrix Composites ◽  
Texture Intensity ◽  
Sic Particles ◽  
Al Matrix

The texture development was investigated in the extruded Al and Al metal matrix composites (MMCs) reinforced with SiC particles of different sizes and volume fractions. During extrusion, both the unreinforced Al and the MMCs develop a strong fiber texture with two components: <111> and <100>. When SiC is introduced into aluminum, the main component of texture is not modified, but the intensity of the component evolves with the volume fraction and average size of SiC particles. For the MMCs reinforced with 3.5μm SiC particles, the texture intensity of the Al matrix tends to decrease as the SiC volume fraction increases, and it is lower than that in the unreinforced Al. However, for the MMCs reinforced with 25 nm and 150 nm SiC particles, the texture intensity of the Al matrix is higher than that in the unreinforced matrix, and it increases with increasing the SiC volume fraction. It is found that superfine particles may introduce some new component into the deformation texture, and the texture intensity increases as the SiC particle size decreases.

A Physics-Based Model for Metal Matrix Composites Deformation During Machining: A Modified Constitutive Equation

2016 ◽  
Vol 139 (1) ◽  
Author(s):  
M. N. A. Nasr ◽  
A. Ghandehariun ◽  
H. A. Kishawy
Keyword(s):  
Particle Size ◽  
Constitutive Equation ◽  
Metal Matrix Composites ◽  
Metal Matrix ◽  
Volume Fraction ◽  
Analytical Models ◽  
Force Model ◽  
Matrix Composites ◽  
New Approach ◽  
Particle Cracking

One of the main challenges encountered in modeling the behavior of metal matrix composites (MMCs) during machining is the availability of a suitable constitutive equation. Currently, the Johnson–Cook (J–C) constitutive equation is being used, even though it was developed for homogeneous materials. In such a case, an equivalent set of homogeneous parameters is used, which is only suitable for a particular combination of particle size and volume fraction. The current work presents a modified form of the J–C constitutive equation that suits MMCs, and explicitly accounts for the effects of particle size and volume fraction, as controlled parameters. Also, an energy-based force model is presented, which considers particle cracking and debonding based on the principles of fracture mechanics. In order to validate the new approach, cutting forces were predicted and compared to experimental results, where a good agreement was found. In addition, the predicted forces were compared to other analytical models available in the literature.

Mechanistic studies in combustion synthesis of NiAl–TiB2 composites: Effects of gravity

2001 ◽  
Vol 16 (6) ◽  
pp. 1614-1625 ◽  
Author(s):  
Cheryl Lau ◽  
Alexander Mukasyan ◽  
Aleksey Pelekh ◽  
Arvind Varma
Keyword(s):  
Particle Size ◽  
Combustion Synthesis ◽  
Combustion Front ◽  
Metal Matrix ◽  
Volume Fraction ◽  
Liquid Solution ◽  
Matrix Composites ◽  
Mechanistic Studies ◽  
Entire Surface ◽  
Microgravity Conditions

Combustion synthesis (CS) of NiAl-based materials reinforced by TiB2 particles was investigated under both terrestrial and microgravity conditions. The synthesized metal matrix composites (MMC) are characterized by very fine (<1 μm) reinforced particulates, which have strong bonding along their entire surface with matrix (NiAl) and are distributed uniformly in it. It was found that microgravity leads to a decrease in the average TiB2 particle size, while higher volume fraction of NiAl component in the material leads to the formation of coarser reinforced particulates. The mechanism of structure formation of different MMCs during CS was identified by using the quenching technique. For example, it was shown that TiB2 grains appear due to crystallization from the complex (Ni–Al–Ti–B) liquid solution formed in the combustion front. An overall decrease of microstructural transformation rates was observed under microgravity.

EFFECT OF AGING ON THE MARTENSITIC TRANSFORMATION CHARACTERISTICS OF A Ni-RICH NiTiHf HIGH TEMPERATURE SHAPE MEMORY ALLOY

2012 ◽  
Vol 05 (04) ◽  
pp. 1250038 ◽  
Author(s):  
ALPER EVIRGEN ◽  
FABIAN BASNER ◽  
IBRAHIM KARAMAN ◽  
RONALD D. NOEBE ◽  
JAUME PONS ◽  
...  
Keyword(s):  
Thermal Stability ◽  
High Temperature ◽  
Precipitation Hardening ◽  
Fine Particles ◽  
Volume Fraction ◽  
Interparticle Spacing ◽  
Precipitate Size ◽  
Short Term ◽  
The Matrix ◽  
Fraction Increase

The effect of aging on the microstructure and transformation temperatures of Ni 50.3 Ti 34.7 Hf 15 was studied. Small interparticle spacing induced by the precipitation of very fine particles, 4–5 nm in size, decreases Ms after short term aging at 450°C and 500°C. The precipitate size and volume fraction increase with aging at longer times and higher temperatures, and as a consequence, Ms increases due to Ni -depletion of the matrix. In general, thermal stability is improved due to precipitation hardening.

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