Experimental and Computational Studies of Competitive Precipitation Behavior Observed in Microstructures with High Dislocation Density and Ultra-Fine Grains

2012 ◽  
Vol 706-709 ◽  
pp. 1787-1792 ◽  
Author(s):  
Tetsuya Masuda ◽  
Shoichi Hirosawa ◽  
Z. Horita ◽  
Kenji Matsuda
Keyword(s):  
Dislocation Density ◽  
Precipitation Hardening ◽  
Volume Fraction ◽  
High Dislocation Density ◽  
Nucleation Theory ◽  
Precipitation Behavior ◽  
The Matrix ◽  
Deformation Processes ◽  
Cold Rolled ◽  
Good Agreement

The competitive precipitation behavior observed in microstructures with high dislocation density and ultra-fine grains has been studied experimentally and computationally for cold-rolled and severe plastic deformed Al-Mg-Si alloy. The age-hardenability at 443K was reduced by the two deformation processes due to the accelerated formation of larger precipitates on dislocations and grain boundaries, in place of the transgranular precipitation of refined β” in the matrix. The developed numerical model based on the classical heterogeneous nucleation theory clarified the dislocation density and grain size dependences of the volume fraction of precipitates nucleated at different sites, in good agreement with experimental results. It could be therefore possible that three strengthening mechanisms of strain hardening, hardening by grain refinement and precipitation hardening are optimally exploited according to the computationally estimated dependences.

The Estimation of Thermal Conductivity for Alumina-Epoxy Composite Material with High Filling Volume Fraction

2014 ◽  
Vol 918 ◽  
pp. 21-26
Author(s):  
Chen Kang Huang ◽  
Yun Ching Leong
Keyword(s):  
Thermal Conductivity ◽  
Composite Material ◽  
Composite Materials ◽  
Physical Model ◽  
Electron Scattering ◽  
Volume Fraction ◽  
Epoxy Composite ◽  
The Matrix ◽  
Transport Theorem ◽  
Good Agreement

In this study, the transport theorem of phonons and electrons is utilized to create a model to predict the thermal conductivity of composite materials. By observing or assuming the dopant displacement in the matrix, a physical model between dopant and matrix can be built, and the composite material can be divided into several regions. In each region, the phonon or electron scattering caused by boundaries, impurities, or U-processes was taken into account to calculate the thermal conductivity. The model is then used to predict the composite thermal conductivity for several composite materials. It shows a pretty good agreement with previous studies in literatures. Based on the model, some discussions about dopant size and volume fraction are also made.

scholarly journals Effects of the Mg/Si Ratio on Microstructure, Mechanical Properties, and Precipitation Behavior of Al–Mg–Si–1.0 wt %-Zn Alloys

Materials ◽  
2018 ◽  
Vol 11 (12) ◽  
pp. 2591 ◽  
Author(s):  
Yong Li ◽  
Guanjun Gao ◽  
Zhaodong Wang ◽  
Hongshuang Di ◽  
Jiadong Li ◽  
...  
Keyword(s):  
Mechanical Properties ◽  
Volume Fraction ◽  
Solution Treatment ◽  
Hardness Test ◽  
Strengthening Effect ◽  
Precipitation Behavior ◽  
Scanning Calorimetry ◽  
First Choice ◽  
The Matrix ◽  
Zn Alloys

Aluminum alloys are widely used as first-choice materials for lightweight automotive applications. It is important that an alloy have a balance between strength and formability. In this study, the alloys were melted, cast, hot rolled, and cold rolled into 1 mm-thick sheets. The microstructure, mechanical properties, and precipitation behavior of Al–Mg–Si–1.0 wt %-Zn alloys with Mg/Si ratios of 0.5, 1, and 2 after solution treatment were studied using optical and electron microscopy, a tensile test, the Vickers hardness test, and differential scanning calorimetry. The results showed that a high density and number of Al–Fe–Si particles were observed in the matrix, thus causing the formation of more homogeneous and smaller recrystallized grains after treatment with the solution. In addition, a higher volume fraction of cubeND and P-types texture components formed during solution treatment. Also, a high r value and excellent deep drawability were achieved in the medium-Mg/Si-ratio alloy. The formation of denser strengthening precipitates led to a better paint-bake hardening effect in comparison with the other two alloys. Furthermore, the precipitation kinetics were enhanced by the addition of Si, and the addition of Zn did not alter the precipitation sequence of the Al–Mg–Si alloy. The dual-phase strengthening effect was not achieved in the studied alloys during paint-bake treatment at 175 °C.

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.

Effect of the Carbon Nanotube Distribution on the Thermal Conductivity of Composite Materials

2015 ◽  
Vol 137 (3) ◽  
Author(s):  
Iman Eslami Afrooz ◽  
Andreas Öchsner
Keyword(s):  
Thermal Conductivity ◽  
Carbon Nanotubes ◽  
Finite Element Analysis ◽  
Composite Materials ◽  
Fiber Volume Fraction ◽  
Volume Fraction ◽  
Fiber Volume ◽  
Element Analysis ◽  
The Matrix ◽  
Good Agreement

Finite element analysis has been employed to investigate the effect of carbon nanotubes (CNTs) distribution on the thermal conductivity of composite materials. Several kinds of representative volume elements (RVEs) employed in this study are made by assuming that unidirectional CNTs are randomly distributed in a polymer matrix. It is also assumed that each set of RVEs contains a constant fiber volume fraction and aspect ratio. Results show that randomness—the way in which fibers are distributed inside the matrix—has a significant effect on the thermal conductivity of CNT composites. Results of this study were compared using the analytical Xue and Nan model and good agreement was observed.

Probability Analysis of the Fuel Microsphere Distribution of Dispersion-Type Nuclear Fuel Plates

2012 ◽  
Author(s):  
Lijun Gao ◽  
Hua Pang ◽  
Bingde Chen ◽  
Shengyao Jiang ◽  
Jiyang Yu ◽  
...  
Keyword(s):  
Normal Distribution ◽  
Volume Fraction ◽  
Reactor Core ◽  
Probability Analysis ◽  
Fission Gas ◽  
The Matrix ◽  
Mini Plate ◽  
Simulation Volume ◽  
Good Agreement

The mechanism of microsphere interconnection through cracks, which is observed in post-irradiation examination of dispersion-type fuel plates for research reactor use and is responsible for blistering, is analyzed. The accumulation of fission gas with burnup and the resulting increase of gas pressure cause the metal matrix to crack and the fuel plate to blister. Based on the experimental observation, a small cylinder in the fuel mini-plate is chosen as the simulation volume. Assuming the diameter of fuel microspheres is identical and in normal distribution separately and the position of fuel microspheres is in uniform random distribution in the matrix, the distribution of fuel volume fraction in the cylinder of the mini-plate is simulated using Monte Carlo method. The analysis shows that the distribution of the fuel volume fraction is in good agreement with the normal distribution. Mini-plates with different fuel volume fractions are further calculated for comparison. The calculation for a full-size plate shows that as for the fuel volume fraction 0.21 and the inventory of reactor core the existence of cylinders with a fuel volume fraction which is susceptible to blistering turns out a possible threat to the fuel reliability. Probability analysis proves to be an effective technique for the quantitative characterization of dispersions.

scholarly journals Mechanical Characteristics of 6063 Aluminum-Steel Dust Composite

2012 ◽  
Vol 2012 ◽  
pp. 1-9 ◽  
Author(s):  
S. O. Adeosun ◽  
E. I. Akpan ◽  
O. I. Sekunowo ◽  
W. A. Ayoola ◽  
S. A. Balogun
Keyword(s):  
Tensile Strength ◽  
Mechanical Characteristics ◽  
Volume Fraction ◽  
Microstructural Analysis ◽  
Eaf Dust ◽  
Solution Treated ◽  
The Matrix ◽  
Cold Rolled ◽  
Steel Dust ◽  
Composite Samples

Studies on the effect of steel dust (EAF dust) addition on the mechanical properties of 6063 Aluminium alloy have been carried out. The cast composite samples contain steel dust from 2–20 wt% produced in sand mould. These cast samples were homogenized, cold rolled, and solution-treated. The solution treated samples were normalized in still air, some quenched in water while some were tempered after quenching. Tensile and hardness responses were determined in all these processed samples. The results obtained reveal that 10 wt% steel dust in aluminium 6063 improved the ultimate tensile strength to 111.09 MPa and a corresponding hardness of 51.2 HV. Microstructural analysis shows iron containing intermetallics which are well distributed in the matrix with its morphology depending on the heat treatment and deformation imposed on them. Tensile strength and hardness of the composites was also found to depend on the volume fraction of intermetallics in the matrix.

Finite Element Modeling of Ceramics Particles Reinforced Aluminum Alloy Composites under Forward Extrusion

2012 ◽  
Vol 548 ◽  
pp. 17-23
Author(s):  
Surasak Suranuntchai
Keyword(s):  
Finite Element ◽  
Metal Forming ◽  
Heat Dissipation ◽  
Volume Fraction ◽  
Matrix Composites ◽  
Area Reduction ◽  
Initial Billet ◽  
The Matrix ◽  
Deformation Processes ◽  
Particulate Reinforced

Finite Element Method (FEM) has becoming more influences in analyzing and solving metal forming problems from the beginning of punch and die designed up to setting the appropriated surrounding constrains in the deformation processes. This research was concerning about the study of simulation in cold forward bar extrusion of some aluminum alloys reinforced with ceramic particles using a commercial FE program; MSC. Marc to enhance the analysis. Two most important parameters in extrusion were investigated, which included area reduction ratio, εA, and die angle, 2∂, that affected to the forming force in the workpiece. In this research, the matrix part of composites studied was varied as follow: AA6061, AA6082 and AA230A reinforced by particles of SiC and Al2O3. Also, the volume fraction of reinforcement was another material parameter needed for the study. The dimension of initial billet in the simulation had 24.7 mm of diameter and 30 mm of length. The punch and die were assumed to be rigid which neglected the deformation. In case of heat dissipation, they were not considered in this simulation; therefore, the process assumed to be done isothermally at room temperature of 20°C. From the modeling results, the suitable conditions for different parameters were obtained, which assisted to the consideration of appropriated forward bar extrusion processes of such particulate reinforced Metal Matrix Composites (MMCs).

scholarly journals Volume Fractions of Tantalum Carbides Deduced from the Ta Contents in the Matrix of Three 1250°C–Aged Cobalt–Based Alloys; Comparison with Thermodynamic Calculations

2020 ◽  
pp. 53-61
Author(s):  
Patrice Berthod
Keyword(s):  
High Temperature ◽  
Volume Fraction ◽  
Thermodynamic Calculations ◽  
Chemical Compositions ◽  
Volume Fractions ◽  
Tantalum Carbides ◽  
Mass Fractions ◽  
The Matrix ◽  
Electron Imaging ◽  
Good Agreement

Some superalloys for service at high temperature under stresses are strengthened by tantalum carbides. Their creep resistance depends on the quantity of TaC and this is the reason why it is often important to control the volume fraction of these carbides in the microstructure. Metallographic preparation followed by electron imaging and surface fraction measurements by image analysis is a frequent way for that. Another possibility is to deduce the mass fraction of TaC, and after their volume fraction, from the chemical composition of the matrix when the alloys are only double–phased, on the {matrix + TaC} type. In this work three alloys – chemically designed to be made exclusively of matrix and TaC – were elaborated and isothermally exposed to an elevated temperature for a duration long enough to allow the alloys being at their thermodynamic equilibria. The chemical compositions of the alloy and of its matrix were measured and the results allowed evaluating their TaC mass fractions which were converted in volume fractions. The obtained TaC fractions were compared to results issued from thermodynamic calculations. Good agreement was found for the three alloys, and this allowed to exploit the used software and thermodynamic database to explore further the microstructures at the same high temperature, notably to know the conditions on the Co, Ni, Cr, Ta and C contents to keep the {matrix + TaC} structure and to avoid any possible partial melting.

scholarly journals Heat Treatment of Cast and Cold Rolled Al–Yb and Al–Mn–Yb–Zr Alloys

Materials ◽  
2021 ◽  
Vol 14 (23) ◽  
pp. 7122
Author(s):  
Veronika Kodetová ◽  
Martin Vlach ◽  
Lucia Bajtošová ◽  
Michal Leibner ◽  
Hana Kudrnová ◽  
...  
Keyword(s):  
Precipitation Hardening ◽  
Positive Influence ◽  
Number Density ◽  
Initial State ◽  
The Matrix ◽  
Cold Rolled ◽  
Relative Resistivity ◽  
The Difference ◽  
20 Nm ◽  
Zr Alloys

The microstructure, electrical properties and microhardness of as-cast and cold rolled AlYb and AlMnYbZr alloys were investigated. The addition of Mn, Yb and Zr has a positive influence on grain size. A deformed structure of the grains with no changes of their size was observed after cold rolling. The Al3Yb particles coherent with the matrix were observed in the AlYb alloys. The size of the particles was about 20 nm in the initial state; after isochronal treatment up to 540 °C the particles coarsen, and their number density was lower. The deformation has a massive effect on the microhardness behavior until treatment at 390 °C, after which the difference in microhardness changes between as-cast and cold rolled alloys disappeared. Relative resistivity changes show a large decrease in the temperature interval of 330–540 °C which is probably caused by a combination of recovery of dislocations and precipitation of the Al3(Yb,Zr) particles. Precipitation hardening was observed between 100 and 450 °C in the AlYb alloy after ageing at 625 °C/24 h and between 330 and 570 °C in the AlMnYbZr alloy after ageing at 625 °C/24 h.

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