scholarly journals Microstructural Evolution and Strengthening Mechanism of SiC/Al Composites Fabricated by a Liquid-Pressing Process and Heat Treatment

Materials ◽  
2019 ◽  
Vol 12 (20) ◽  
pp. 3374 ◽  
Author(s):  
Sangmin Shin ◽  
Seungchan Cho ◽  
Donghyun Lee ◽  
Yangdo Kim ◽  
Sang-Bok Lee ◽  
...  
Keyword(s):  
Heat Treatment ◽  
Compressive Strength ◽  
Microstructural Evolution ◽  
Load Transfer ◽  
Volume Fraction ◽  
High Volume ◽  
Strengthening Mechanism ◽  
Spherical Particles ◽  
Pressing Process ◽  
Liquid Pressing Process

Aluminum alloy (Al7075) composites reinforced with a high volume fraction of silicon carbide (SiC) were produced by a liquid-pressing process. The characterization of their microstructure showed that SiC particles corresponding to a volume fraction greater than 60% were uniformly distributed in the composite, and Mg2Si precipitates were present at the interface between the matrix and the reinforcement. A superior compressive strength (1130 MPa) was obtained by an effective load transfer to the hard ceramic particles. After solution heat treatment and artificial aging, the Mg2Si precipitates decomposed from rod-shaped large particles to smaller spherical particles, which led to an increase of the compressive strength by more than 200 MPa. The strengthening mechanism is discussed on the basis of the observed microstructural evolution.

Development of High Strength Alloys in the Mg-Ni-Y-RE System

2007 ◽  
Vol 567-568 ◽  
pp. 385-388 ◽  
Author(s):  
P. Pérez ◽  
S. González ◽  
G. Garcés ◽  
G. Caruana ◽  
P. Adeva
Keyword(s):  
Magnesium Alloy ◽  
Load Transfer ◽  
Volume Fraction ◽  
Hot Extrusion ◽  
High Strength ◽  
High Volume ◽  
Magnesium Matrix ◽  
Fine Grained ◽  
Matrix Embedding ◽  
Second Phases

The microstructural and mechanical characterization of two alloys within the Mg-Ni-YRE system prepared by casting and subsequent hot extrusion at 400°C have been carried out. The microstructure of both materials consists of a fine-grained magnesium matrix embedding a high volume fraction of second phases; coarse Mg12RE and long period ordered stacking structure (LPS phase) and fine Mg2Ni particles. Both alloys show high strength values up to 250°C. The yield stress values at room temperature are 295 and 405 MPa for low- and high-alloyed magnesium alloy, respectively. Load transfer from the magnesium matrix to coarse Mg12RE and LPS particles account for the high strength of both alloys at temperatures below 250°C. Above this temperature both alloys exhibit a superplastic behaviour at low stresses with elongations of 700 and 450 % for the low and high-alloyed magnesium alloy, respectively.

Optimization of the Solution Heat Treatment of Rheo-High Pressure Die Cast Al-Cu-Mg-Ag 2139 Alloy

2015 ◽  
Vol 828-829 ◽  
pp. 226-231 ◽  
Author(s):  
Pfarelo Daswa ◽  
Heinrich Möller ◽  
Gonasagren Govender
Keyword(s):  
Heat Treatment ◽  
High Pressure ◽  
Aluminium Alloy ◽  
Solution Heat Treatment ◽  
Volume Fraction ◽  
High Volume ◽  
Single Step ◽  
Incipient Melting ◽  
Scanning Calorimetry ◽  
Die Cast

This paper investigates the optimization of the solution heat treatment parameters of the rheo-high pressure die cast (R-HPDC) 2139 aluminium alloy. Differential Scanning Calorimetry (DSC) and optical microscopy were used to investigate the incidence of incipient melting and therefore determine suitable solution heat treatment temperatures. A three-step solution heat treatment where the alloy was heat treated from 400°C to 513°C using controlled heating conditions and held at 513°C for 2 hours and finally heated up from 513°C to 525°C and held there for 16 hours was done. R-HPDC is known to produce surface liquid segregation and when processing the alloys these areas are most prone to incipient melting. The applicability of a single (525°C for 16h) and three-step solution heat treatments on the R-HPDC 2139 aluminium alloy was also investigated. A single-step solution heat treatment results in incipient melting, whereas this is mostly eliminated using the three-step solution heat treatment. However, a high volume fraction of undissolved phases remain in the liquid segregated areas, even after the three-step solution heat treatment.

scholarly journals High Temperature Mechanical Properties and Wear Performance of B4C/Al7075 Metal Matrix Composites

Metals ◽  
2019 ◽  
Vol 9 (10) ◽  
pp. 1108 ◽  
Author(s):  
Sangmin Shin ◽  
Donghyun Lee ◽  
Yeong-Hwan Lee ◽  
Seongmin Ko ◽  
Hyeonjae Park ◽  
...  
Keyword(s):  
High Temperature ◽  
Fracture Mechanism ◽  
Room Temperature ◽  
Volume Fraction ◽  
Microstructural Analysis ◽  
Wear Loss ◽  
Matrix Composites ◽  
Pressing Process ◽  
Liquid Pressing Process ◽  
Al Matrix

In this study, high volume fraction B4C reinforced Al matrix composites were fabricated with a liquid pressing process. Microstructural analysis by scanning electron microscope and a transmission electron microscopy shows a uniform distribution of the B4C reinforcement in the matrix, without any defects such as pore and unwanted reaction products. The compressive strength and wear properties of the Al7075 matrix and the composite were compared at room temperature, 100, 200, and 300 °C, respectively. The B4C reinforced composite showed a very high ultimate compression strength (UCS) over 1.4 GPa at room temperature. The UCS gradually decreased as the temperature was increased, and the UCS of the composite at 300 °C was about one third of the UCS of the composite at room temperature. The fractography of the compressive test specimen revealed that the fracture mechanism of the composites was the brittle fracture mode at room temperature during the compression test. However, at the elevated temperature, AMCs had a mixed mode of a brittle and ductile fracture mechanism under the compressive load. The composite produced by a liquid pressing process also showed superior wear resistance compared with the Al matrix. The result of the wear test indicates that the wear loss of the Al matrix at 300 °C was two times higher than that of the AMCs, which is attributed to the formation of a mechanically mixed layer (MML) in the composites at the high temperature.

scholarly journals Fabrication of TiB2–Al1050 Composites with Improved Microstructural and Mechanical Properties by a Liquid Pressing Infiltration Process

Materials ◽  
2020 ◽  
Vol 13 (7) ◽  
pp. 1588
Author(s):  
Seongmin Ko ◽  
Hyeonjae Park ◽  
Yeong-Hwan Lee ◽  
Sangmin Shin ◽  
Ilguk Jo ◽  
...  
Keyword(s):  
Mechanical Properties ◽  
High Temperature ◽  
Metal Matrix ◽  
Load Transfer ◽  
Volume Fraction ◽  
High Volume ◽  
Matrix Composites ◽  
Infiltration Process ◽  
Al Composite ◽  
Al Matrix

This study was conducted on titanium diboride (TiB2) reinforced Al metal matrix composites (MMCs) with improved properties using a TiB2 and aluminum (Al) 1050 alloy. Al composites reinforced with fine TiB2 at volume ratios of more than 60% were successfully fabricated via the liquid pressing infiltration (LPI) process, which can be used to apply gas pressure at a high temperature. The microstructure of the TiB2–Al composite fabricated at 1000 °C with pressurization of 10 bar for 1 h showed that molten Al effectively infiltrated into the high volume-fraction TiB2 preform due to the improved wettability and external gas pressurization. In addition, the interface of TiB2 and Al not only had no cracks or pores but also had no brittle intermetallic compounds. In conclusion, TiB2–Al composite, which has a sound microstructure without defects, has improved mechanical properties, such as hardness and strength, due to effective load transfer from the Al matrix to the fine TiB2 reinforcement.

Research on Microstructure and Wear Resistance of (Fe,Cr)7C3/Fe Surface Gradient Composite

2015 ◽  
Vol 1120-1121 ◽  
pp. 559-563
Author(s):  
Chong Wang ◽  
Fang Xia Ye ◽  
Li Sheng Zhong ◽  
Ying Lin Yan ◽  
Yu Jun Lai ◽  
...  
Keyword(s):  
Heat Treatment ◽  
Wear Resistance ◽  
Volume Fraction ◽  
Subsurface Layer ◽  
Composite Layer ◽  
High Volume ◽  
Synthesis Process ◽  
X Ray Diffraction ◽  
Surface Gradient

In this study, the (Fe,Cr)7C3 particles strengthened gradient composite was produced by in situ synthesis process with subsequent heat treatment from gray cast iron (HT300) and high purity chrome plate. The microstructure, phase composition and wear resistance of the composite were studied by scanning electron microscopy (SEM), X-ray diffraction (XRD) and scratch tester. The results showed that the thickness of the gradient layer was about 758 μm after heat treatment at 900 °Cfor 4 h. And it can be divided into three areas depending on microstructure. The outermost layer which was ~60 μm of thickness, was the dense ceramic layer with high volume fraction of (Fe,Cr)7C3 ~90%. No obvious grain boundaries were observed. The subsurface layer was the particles dispersed layer, which was ~525 μm of thickness, with the volume fraction of (Fe,Cr)7C3 decreased to 70%. The lowermost layer was ferrite, with about 173 μm thickness. A good metallurgical bond generated between the composite layer and matrix. The depth and the width of surface scratch increased with the raising loads from 0 to 100 N, and the cracks mainly included micro-crack, tiny dens crack, mixture crack and through-wall crack. The (Fe,Cr)7C3 particles were broken and scraped when the load exceeded 80 N.

Numerical prediction of thermal conductivity in ZrB2-particulate-reinforced epoxy composites based on finite element models

2018 ◽  
Vol 25 (2) ◽  
pp. 337-342
Author(s):  
Yicheng Wu ◽  
Zhiqiang Yu
Keyword(s):  
Thermal Conductivity ◽  
Finite Element ◽  
Volume Fraction ◽  
High Volume ◽  
Epoxy Composites ◽  
Spherical Particles ◽  
Homogeneous Distribution ◽  
Finite Element Models ◽  
Negative Effect ◽  
Thermal Conductivities

AbstractEpoxy composites reinforced by Zirconium diboride (ZrB2) particles were investigated by finite element models (FEMs). It helped to explore the relationship between the thermal conductivity of composites and the volume fraction, size, shape, orientation, and arrangement of the ZrB2particles. The results showed that the thermal conductivity performance of composites was improved effectively when filled with ZrB2particles. Specifically, epoxy composites filled with 50 vol% spherical ZrB2particles had 12.05 times the thermal conductivity of epoxy resin. At the same volume fraction, the number of ZrB2particles in the epoxy matrix has little influence on thermal conductivity due to the dimensionless models. At a high volume fraction, rectangular ZrB2particles improved thermal conductivity more effectively than spherical particles. In the comparison of thermal conductivities among composites reinforced by rectangular fillers, the thermal conductivities of composites were clearly affected by the length-width ratios of fillers, and this effect was monotonically increasing. The vertical orientations of particles could conduct heat most effectively compared with slant and parallel orientations. The agglomerate distribution of ZrB2particles has the negative effect of thermal diffusion in a certain direction compared with homogeneous distribution.

Enhanced thermal conductivity of epoxy/alumina composite through multiscale-disperse packing

2020 ◽  
Vol 55 (1) ◽  
pp. 17-25
Author(s):  
Hongkun Li ◽  
Weidong Zheng
Keyword(s):  
Thermal Conductivity ◽  
Volume Fraction ◽  
Mean Field ◽  
High Volume ◽  
Theory Model ◽  
Spherical Particles ◽  
Particle Sizes ◽  
Interfacial Resistance ◽  
Steady State Method ◽  
Cure Shrinkage

Inspired by the size of the voids in closest packing structures, we propose to use the combination of spherical particles with different size scales to increase the loading fraction of the fillers in epoxy-based composites. In this study, high loading up to 79 vol% has been achieved with multiscale particle sizes of spherical Al2O3 particles. The highest thermal conductivity of Al2O3-filled liquid epoxy measured by steady-state method is 6.7 W m−1 K−1 at 25°C, which is approximately 23 times higher than the neat epoxy (0.28 W m−1 K−1). Three models based on Maxwell mean-field scheme (MMF), differential effective medium (DEM) and percolation theory model (PTM) were utilized to assess our measured thermal conductivity data. We found that both DEM and PTM models could give good results at high volume fraction regime. We have also observed a considerable reduction (10–15%) of thermal conductivity in our Al2O3-filled cured epoxy samples. We attribute this reduction to the increasing of thermal interfacial resistance between Al2O3 particles and cured epoxy matrix, induced by cure shrinkage during the reaction. Our experiments have demonstrated that systems with multiscale particle sizes exhibit lower viscosity and can be filled with much higher fraction of fillers. We thus expect that higher thermal conductivity (probably >12 W m−1 K−1 based on DEM) can be achieved in future via filling higher thermal conductivity spherical fillers (e.g., AlN, SiC), increasing loading fraction by multiscale-disperse packing and reducing the effect from cure shrinkage.

scholarly journals Mix design of high-volume fly ash ultra high performance concrete

2021 ◽  
Vol 15 (4) ◽  
pp. 197-208
Author(s):  
Nguyen Van Tuan ◽  
Pham Sy Dong ◽  
Le Trung Thanh ◽  
Nguyen Cong Thang ◽  
Yang Keun Hyeok
Keyword(s):  
Heat Treatment ◽  
Compressive Strength ◽  
Fly Ash ◽  
Co2 Emissions ◽  
High Performance ◽  
High Performance Concrete ◽  
High Volume ◽  
Mix Design ◽  
Ultra High Performance Concrete ◽  
High Volume Fly Ash

The addition of supplementary cementitious materials (SCMs) to replace cement, especially with a high volume (> 50%), is an effective way to reduce the environmental impact due to the CO2 emissions generated in the production of ultra-high performance concrete (UHPC). Unfortunately, no official guidelines of UHPC using a high volume of SCMs have been published up to now. This paper proposes a new method of mix design for UHPC using high volume fly ash (HVFA), that is referred to the particle packing optimization of the Compressive Packing Model proposed by F. de Larrard. This proposed method also considers the heat treatment curing duration to maximize the compressive strength of HVFA UHPC. The experimental results using this proposed mix design method show that the optimum fly ash content of 50 wt.% of binder can be used to produce HVFA UHPC with a compressive strength of over 120 MPa and 150 MPa under standard curing and heat treatment, respectively. Moreover, the embodied CO2 emissions of UHPC reduces 56.4% with addition of 50% FA.

Precipitation Sequence in an Al-Si-Mg Foundry Alloy

2010 ◽  
Vol 654-656 ◽  
pp. 590-595 ◽  
Author(s):  
Barbara Rinderer ◽  
Malcolm Couper ◽  
Xiang Yuan Xiong ◽  
Sam X. Gao ◽  
Jian Feng Nie
Keyword(s):  
Heat Treatment ◽  
Sample Preparation ◽  
Recent Work ◽  
Volume Fraction ◽  
Eutectic Silicon ◽  
High Volume ◽  
Coarse Particles ◽  
Precipitation Sequence ◽  
Foundry Alloy ◽  
Foundry Alloys

It is often assumed that the precipitation sequence and phases in Al-Si-Mg foundry alloys, such as A356 with 7 wt%Si, are similar to those in wrought 6xxx Al-Mg-Si alloys, such as 6063. The foundry alloys have been less extensively studied due to added difficulties in sample preparation, resulting from the high volume fraction of coarse particles of spheroidised eutectic silicon. Recent work has been successful in studying the precipitation sequence in a foundry alloy containing 0.45 wt%Mg. The work highlights some differences and similarities between foundry and wrought alloy precipitation, which may have implications for alloy design and heat-treatment.

scholarly journals An Investigation of the Effects of Volume Fraction on Drag Coefficient of Non-Spherical Particles Using PR-DNS

2021 ◽  
Author(s):  
Pratik Mahyawansi ◽  
Cheng-Xian Lin
Keyword(s):  
Drag Coefficient ◽  
Cfd Simulation ◽  
Volume Fraction ◽  
Fixed Bed ◽  
Reynold Number ◽  
High Volume ◽  
Momentum Equation ◽  
Spherical Particles ◽  
Computational Time ◽  
The Impact

Abstract Prediction of the drag coefficient is required in gas-particle multiphase flow modeling and simulation. Experimental data and correlations on the fixed-bed system of spherical particles with high volume fractions for various possible arrangements are available in the literature. However, the effect of volume fraction on the drag coefficient of non-spherical particles is not well studied. In solving the momentum equation, the volume fraction plays a vital role in determining the flow resistances. In this paper, we study the impact of volume fraction in the range of 0.069 to 0.65 on the drag coefficient using the computational fluid dynamics (CFD) simulation of air for Reynold number in the range of 10 to 10000 using particle resolved direct numerical solution (PR-DNS). Regular non-spherical particles such as a cube, tetrahedron, and spheroids are used in this study since their single particle’s drag coefficient data are available in the literature for comparison. For this work, the simulations are carried out in the Ansys Fluent using polyhedral mesh, which consumes significantly less computational time and power. The study showed the sphericity and volume fraction have significant impact on the bed pressure drop and average drag coefficient of the particles in the bed especially in high Reynolds number regime. The bed of the spheroid experiences the lowest drag being the most streamlined particle, and the particles with the edges result in a large drag coefficient due to flow separation at the discontinuity. The vector plots verify this behavior where large wake regions are observed behind the tetrahedron particle.

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