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1.
Inclusion distribution was studied in commercial aluminum DC-cast billets and slabs using a newly developed deep-etching method.
Analyses revealed a nonuniform distribution of nonmetallic inclusions across billet diameters and lengths, and also across
slab thicknesses and widths. In as-cast billets, more inclusions were found at the beginning and end of the billet length;
more were present near the cross-section center than near the surface. In slabs, inclusions were located mostly within 13 mm
of the surface and in a band between the centerline and the surface. Few inclusions were found 60 to 100 mm from the slab
surface or at the centerline. In addition, comparing slab quality after casting using three types of ceramic foam filters
(CFFs; i.e., 30 ppi, 50 ppi, and 50 ppi + HF) revealed significant differences in inclusion size, number, and distribution. Casting slabs
using a finer pore-size filter (50 ppi) reduced the number of non-metallic inclusions greatly. The inclusion distribution
patterns observed in the solidified slabs are discussed in terms of melt flow during casting. 相似文献
2.
Arjan Ciftja Thorvald Abel Engh Merete Tangstad 《Metallurgical and Materials Transactions B》2010,41(1):146-150
Filtration with foam filters is reported as a successful method to remove inclusions from top-cut silicon scrap. Inclusions
in top-cut silicon scrap are needle-like Si3N4 particles and round SiC inclusions. A high filtration efficiency of more than 99 pct for 30-ppi SiC filters is achieved.
The inclusions that remain are mainly SiC particles smaller than 10 μm. Possibly these particles are primarily secondary inclusions.
The filtration efficiency increases with decreasing filter pore size. The main factor that plays a role in deep-bed filtration
seems to be interception. Various models are considered to estimate the removal efficiency of foam filters by this mechanism.
Here, we propose a new model called “the branch” model. This model gives a high filtration efficiency and agrees the best
with the experimental results. 相似文献
3.
M. Zhou D. Shu K. Li W. Y. Zhang H. J. Ni B. D. Sun J. Wang 《Metallurgical and Materials Transactions A》2003,34(5):1183-1191
The inclusions in molten aluminum were removed using the deep filtration of ceramic foam filters and ceramic particles with
active coatings. The results of tensile tests showed that the elongation of the filtered tensile specimen S6 increases by 17.93 pct, but the tensile strength does not. The scanning electron microscope (SEM) examination showed that
the secondary cracks and dimples in the filtered tensile specimen S6 were finer and more homogeneous than those in the unfiltered tensile specimen S0. In addition, metallographic examination showed that there were only a few inclusions of approximately 6 μm in diameter in the filtered specimen S6, but more inclusions of approximately 40 μm in diameter were found in the unfiltered specimen S0. The filtration efficiency of the coated ceramic particles was higher than that of the coated ceramic foam filters. The active
coating could effectively capture the inclusions and dissolve Al2O3 in them during filtration. 相似文献
4.
S. B. Venkata Siva K. L. Sahoo R. I. Ganguly R. R. Dash S. K. Singh B. K. Satpathy G. Srinivasarao 《Metallurgical and Materials Transactions B》2013,44(4):800-808
A novel method is adapted to prepare an in situ ceramic composite from waste colliery shale (CS) material. Heat treatment of the shale material, in a plasma reactor and/or in a high temperature furnace at 1673 K (1400 °C) under high vacuum (10?6 Torr), has enabled in situ conversion of SiO2 to SiC in the vicinity of carbon and Al2O3 present in the shale material. The composite has the chemical constituents, SiC-Al2O3-C, as established by XRD/EDX analysis. Particle sizes of the composite range between 50 nm and 200 μm. The shape of the particles vary, presumably rod to spherical shape, distributed preferably in the region of grain boundaries. The CS composite so produced is added to aluminum melt to produce Al-CS composite (12 vol. pct). For comparison of properties, the aluminum metal matrix composite (AMCs) is made with Al2O3 particulates (15 vol. pct) with size <200 μm. The heat-treated Al-CS composite has shown better mechanical properties compared to the Al-Al2O3 composite. The ductility and toughness of the Al-CS composite are greater than that of the Al-Al2O3 composite. Fractographs revealed fine sheared dimples in the Al-CS composite, whereas the same of the Al-Al2O3 composite showed an appearance of cleavage-type facets. Abrasion and frictional behavior of both the composites have been compared. The findings lead to the conclusion that the in situ composite developed from the colliery shale waste material has a good future for its use in AMCs. 相似文献
5.
Gaoyang Song Bo Song Zhancheng Guo Yuhou Yang Mingming Song 《Metallurgical and Materials Transactions B》2018,49(1):34-44
An innovative method for separating non-metallic inclusions from a high temperature melt using super gravity was systematically investigated. To explore the separation behavior of inclusion particles with densities less than that of metal liquid under a super-gravity field, a Fe-Al-O melt containing Al2O3 particles was treated with different gravity coefficients. Al2O3 particles migrated rapidly towards the reverse direction of the super gravity and gathered in the upper region of the sample. It was hard to find any inclusion particles with sizes greater than 2 μm in the middle and bottom areas. Additionally, the oxygen content in the middle region of the sample could be reduced to 0.0022 mass pct and the maximum removal rate of the oxygen content reached 61.4 pct. The convection in the melt along the direction of the super gravity was not generated by the super-gravity field, and the fluid velocity in the molten melt consisted only of the rotating tangential velocity. Moreover, the motion behavior of the Al2O3 particles was approximatively determined by Stokes’ law along the direction of super gravity. 相似文献
6.
Lucas Nana Wiredu Damoah Lifeng Zhang 《Metallurgical and Materials Transactions B》2010,41(4):886-907
Filtration experiments were carried out using both an AlF3 slurry-coated and an uncoated Al2O3 ceramic foam filter to study the removal of nonmetallic inclusions and impurity elements. The results showed that the 30-ppi
ceramic foam filter removed up to 85 pct inclusions from aluminum. Several pictures of two- and three-dimensional morphologies
of both nonmetallic and intermetallics inclusions also have been presented. The following contributing mechanisms for the
removal of nonmetallic inclusions in the deep-bed filtration mode are proposed: (1) collision with walls and interception
effect and (2) the formation of both intermetallic and nonmetallic inclusion bridges during filtration. Fluid dynamics modeling
of inclusion attachment to the filter walls showed that most inclusions, especially those with larger sizes, are entrapped
at the upper part of the filter, whereas smaller inclusions are dispersed well throughout the filter. The calculated inclusions
removal fractions for the 30-ppi filter showed that almost all inclusions >125 μm are removed, and inclusions ~5 μm in size
are removed up to 85 pct. The interfacial energy between two collided same-size inclusions was calculated, indicating that
a strong clustering of inclusions may result within the filter window. Magnesium impurities were removed up to 86 pct by the
AlF3 slurry-coated filter. The filter acted in active filtration mode in addition to the contribution of the air oxidation of
dissolved [Mg], which was calculated to be 13 pct. The total mass transfer coefficient of dissolved [Mg] to the reaction interface
was calculated to be 1.15 × 10−6 m/s. 相似文献
7.
A new process for the preparation and casting of metal-particulate non-metal composites is described. Particulate composites
of ceramic oxides and carbides and an Al-5 pet Si-2 pct Fe matrix were successfully prepared. From 10 to 30 wt pct of A12O3, SiC, and up to 21 wt pct glass particles, ranging in size from 14 to 340 ώ were uniformly distributed in the liquid matrix
of a 0.4 to 0.45 fraction solid slurry of the alloy. Initially, the non-wetted ceramic particles are mechanically entrapped,
dispersed and prevented from settling, floating, or agglomerating by the fact that the alloy is already partially solid. With
increasing mixing times, after addition, interaction between the ceramic particles and the liquid matrix promotes bonding.
Efforts to mix the non-wetted particles into the liquid alloy above its liquidus temperature were unsuccessful. The composite
can then be cast either when the metal alloy is partially solid or after reheating to above the liquidus temperature of the
alloy. End-chilled plates and cylindrical slugs of the composites were sand cast from above the liquidus temperature of the
alloy. The cylindrical slugs were again reheated and used as starting material for die casting. Some of the reheated composites
possessed “thixotropy.” Distribution of the ceramic particles in the alloy matrix was uniform in all the castings except for
some settling of the coarse, 340ώ in size, particles in the end-chilled cast plates. 相似文献
8.
T. A. Chernyshova L. I. Kobeleva I. E. Kalashnikov L. K. Bolotova 《Russian Metallurgy (Metally)》2009,(1):70-76
The effect of SiO2 and Al2O3 oxide ceramic nanoparticles on the solidification of model samples based on a commercial D16 alloy is studied. The composite samples are fabricated by reaction casting when titanium, nickel, and ceramic powders are mixed with an aluminum melt. The grain size in a matrix, the size and shape of Al3Ti intermetallic inclusions, and the interphase distances in eutectics are determined with optical and scanning electron microscopes. A certain modifying effect of oxide ceramic nanoparticles on the structure of model CMs during their in situ formation is detected, and the inoculation effect of SiO2 added to a melt on the reaction products is most pronounced. 相似文献
9.
Joo Hyun Park 《Metallurgical and Materials Transactions B》2007,38(4):657-663
10.
Aluminum hard particle composites were synthesized by the solidification processing technique and the composite melt was solidified
using gravity and pressure die castings. An aluminum-silicon alloy (A 332.1) has been used as the matrix and silicon carbide
particles (quantity: 10 wt pct, and size: 50 to 80 μm) have been used as reinforcement for synthesis of the composite. The microstructure of the pressure die cast composite is
found to be finer than those of the gravity cast ones. Additionally, the distribution of SiC particles in the Al alloy matrix
is found to be more uniform in the pressure die-cast composites compared to the gravity die-cast ones. The mechanical properties
such as ultimate tensile strength, hardness, and ductility are observed to be superior in the case of pressure die-cast composites
compared to the gravity-cast one. The two-body abrasive wear resistance of the Al-composite is also noted to be greater in
the pressure die-cast composite than in the gravity-cast one. The effects of injection pressure on the mechanical properties
and wear resistance of the pressure die-cast composites are examined. It is observed that the wear resistance (inverse of
wear rate), hardness, and strength of the Al-SiC composites increase with the increase in injection pressure during pressure
die casting. This may be due to the finer microstructure, the absence of casting defects, and the stronger interfacial bonding
between the matrix and hard dispersoid in pressure die-cast composites. The wear rate of the alloys and composites is studied
as a function of their hardness, strength, and Young’s modulus. It is noted that the wear rate is primarily controlled by
hardness even though other mechanical properties influence the wear behavior of the materials to some extent. An attempt is
made to establish an empirical relation to correlate the wear rate of material with the mechanical properties such as hardness,
ultimate tensile strength, and elongation. 相似文献
11.
Electron and laser beam welding of high strain rate superplastic Al-6061/SiC composites 总被引:6,自引:0,他引:6
R. Y. Huang J. C. Huang S. C. Chen 《Metallurgical and Materials Transactions A》2001,32(10):2575-2584
The welding characteristics of a fine-grained 6061 Al and three 6061/1, 5, and 20 pct SiC composites under high energy electron
beam welding (EBW) and laser beam welding (LBW) were examined. The three composites exhibited high strain rate superplasticity
(HSRS). The 6061 Al was more readily welded by EBW than by LBW, and the situation was reversed in the reinforced composites.
In the reinforced composites, the fusion zone contained the once fully melted matrix and fully reacted SiC, and the heat affected
zone (HAZ) contained the partially melted matrix and nearly unreacted SiC. This effect was particularly apparent in the 20
pct SiC composite. With increasing SiC content from 0 to 20 pct, the reflection of the laser beam decreased, and the melt
viscosity increased due to the increasing amount of Al4C3 compounds. For the HSRS fine-grained 6061/20 pct SiC composite, there formed a sharp V-notch under EBW. The high viscosity
or low fluidity of the melt inside the fusion zone of 6061/20 pct SiC resulted in incomplete backfill and notch formation.
The postweld mechanical performance and joint efficiency both became seriously degraded. The original fine structures in the
HSRS composites could not be restored after welding. 相似文献
12.
The present paper deals with the development of metal matrix composites with improved mechanical properties based on metastable austenitic TRIP‐steel and magnesia partially stabilised zirconia. The ceramic material is characterised regarding the influence of different additives (MgAl2O4, MgO, Al2O3) on the monoclinic/tetragonal/cubic phase composition. First results for the infiltration of ceramic preforms are shown, on the one hand performed by conventional steel casting technology and on the other hand by submerging of preforms in a metal melt using a steel casting simulator. 相似文献
13.
Wanlin Wang Jie Yu Lejun Zhou Zhaoyang Wu Huan Li 《Metallurgical and Materials Transactions B》2018,49(4):1580-1587
To compensate the negative effect caused by the absorption of chromium oxide inclusions during the casting process of Cr-contained steels, a new mold flux system has been designed and investigated. The melting temperature range of the newly designed mold flux system is from [1124 K to 1395 K (851 °C to 1122 °C)]. The viscosity at 1573 K (1300 °C) and the break temperature increase with the addition of MnO and Cr2O3 but decrease with the addition of B2O3. The crystalline fraction of mold flux decreases from 81 to 42.1 pct with the addition of MnO and Cr2O3, and then further decreases to 25.3 pct with the addition of B2O3; however, it improves from 54.4 to 81.5 pct when the basicity increases. Besides, the heat-transfer ability of mold flux is inverse to the crystallization ratio of the slag. The comprehensive study of the properties for the four designed mold fluxes suggests that the mold flux with 1.15 basicity-3.01 pct B2O3-1.10 pct MnO-2.10 pct Cr2O3 shows the best properties for the continuous casting of Cr-contained steels. 相似文献
14.
A magnesium-based composite with 1.1 volume percentage of nanosized Al2O3 particulates reinforcement was fabricated using an innovative disintegrated melt deposition technique followed by hot extrusion.
Al2O3 particulates with an equivalent size of 50 nm were used as reinforcement. Microstructural characterization of the materials
revealed grain refinement of magnesium matrix due to incorporation, retention, and uniform distribution of reinforcement.
Physical properties characterization revealed that the addition of nano-Al2O3 particulates as reinforcement improves the dimensional stability of pure magnesium. Mechanical properties characterization
revealed that the presence of nano-Al2O3 particulates as reinforcement leads to a significant increase in microhardness, dynamic elastic modulus, 0.2 pct yield strength
(YS), ultimate tensile strength (UTS), and ductility of pure magnesium. The results revealed that the combined tensile properties
of these materials are superior when compared to Mg reinforced with much higher volume percentage of SiC. An attempt is made
in the present study to correlate the effect of nano-Al2O3 particulates as reinforcement with the microstructural, physical, and mechanical properties of magnesium. 相似文献
15.
A micromechanical model is developed to compute the stress-strain curve of particle-reinforced metal-matrix composites under
monotonic and cyclic deformation. The composite was modeled as a three-dimensional array of hexagonal prisms, each containing
an intact or fractured reinforcement. The average stresses acting on the intact and damaged cells—as well as on the ceramic
particles —were computed from the finite-element analysis of axisymmetric cylindrical cells, and the overall composite response
was then calculated through an isostrain approach. The model was validated against the experimental results, reported in Parts
I and II of this article, for an 8090 Al alloy reinforced with 15 vol pct SiC particles,[1,2] where the matrix and reinforcement properties were obtained from mechanical tests on the unreinforced alloy and from quantitative
microscopy analyses of the fraction of broken reinforcements in the composite. The critical mechanisms which controlled the
deformation and damage processes in the composite during monotonic and cyclic deformation are discussed in light of the model
results. 相似文献
16.
Youming Liu Wenyi Li Xun Cai Liuhe Li Qiulong Chen Bofan Xu 《Metallurgical and Materials Transactions A》2004,35(8):2511-2515
Rare earth CeO2 was investigated as an additive for in-situ preparation of TiC/Al composites using XD (exothermal dispersion) + casting technology. Experiment results showed that an
optimum CeO2 addition of 0.5 wt pct promotes the generation and refinement of TiC particles, prevents the formation of Al3Ti, increases the wettability between the TiC ceramic particles and the Al matrix, and improves the mechanical properties
of composite. A corresponding thermodynamic model was proposed for the mechanism. 相似文献
17.
T. A. Chernyshova L. I. Kobeleva L. K. Bolotova I. V. Katin 《Russian Metallurgy (Metally)》2013,2013(3):220-228
The structure and interfacial interaction are studied in the hybrid aluminum-matrix composite materials fabricated by reactive casting combined with mechanical mixing of fillers with a metallic melt. The following types of hardening are considered: hardening by ceramic particles and by the phases formed as isolated inclusions or coatings on ceramic particles during in situ reactions. The hardness and tribological properties of the composite materials as functions of their compositions are discussed. 相似文献
18.
A micromechanical model is developed to compute the stress-strain curve of particle-reinforced metal-matrix composites under
monotonic and cyclic deformation. The composite was modeled as a three-dimensional array of hexagonal prisms, each containing
an intact or fractured reinforcement. The average stresses acting on the intact and damaged cells — as well as on the ceramic
particles — were computed from the finite-element analysis of axisymmetric cylindrical cells, and the overall composite response
was then calculated through an isostrain approach. The model was validated against the experimental results, reported in Parts
I and II of this article, for an 8090 Al alloy reinforced with 15 vol pct SiC particles,[1,2] where the matrix and reinforcement properties were obtained from mechanical tests on the unreinforced alloy and from quantitative
microscopy analyses of the fraction of broken reinforcements in the composite. The critical mechanisms which controlled the
deformation and damage processes in the composite during monotonic and cyclic deformation are discussed in light of the model
results. 相似文献
19.
This article describes a theoretical model and an experimental method for determination of interphasial elastic moduli in
high-temperature composites. The interphasial moduli are calculated from the ultrasonically measured composite modulivia inversion of multiphase micromechanical models. Explicit equations are obtained for determination of interphasial stiffnesses
for an interphase model with spring boundary conditions and multiphase fiber. The results are compared with the exact multiphase
representation. The method was applied to ceramic and intermetallic matrix composites reinforced with SiC SCS-6 fibers. In
both composites, the fiber-matrix interphases include approximately 3-μm-thick carbon-rich coatings on the outer surface of
the SiC shell. Although the same fiber is used in both composite systems, experimental results indicate that the effective
interphasial moduli in these two composite systems are very different. The interphasial moduli in intermetallic matrix composites
are much greater than those in ceramic matrix composites. After taking the interphase microstructure into account, we found
that the interphasial moduli measured for the intermetallic matrix composites are very close to the estimated bulk moduli
of the pyrolytic carbon with SiC particle inclusions. Our analysis shows that the lower effective interphasial moduli in the
reaction-bonded Si3N4 (RBSN) ceramic matrix composites are due to imperfect contact between the interphasial carbon and the porous matrix and to
thermal tension forces which slightly unclamp the interphase. Thus, measured interphase effective moduli give information
on the quality of mechanical contact between fiber and matrix. Possible errors in the interphasial moduli determined are analyzed
and the results show that these errors are below 10 pct. In addition, the use of the measured interphasial moduli for assessment
of interphasial damage and interphase reactions is discussed. 相似文献
20.
《Canadian Metallurgical Quarterly》2013,52(4):311-318
AbstractLaboratory prepared melts of steel containing Al2O3 inclusions and aluminum containing TiB2 inclusions have been successfully filtered using multicellular extruded ceramic filters. Relatively high inclusion removal efficiencies have been achieved in both low temperature and high temperature melt systems —68 % inclusion removal efficiency in the Al-TiB2 system (1020 K) using cordierite multicellular filters and 96 % inclusion removal efficiency in the steel–Al2O3 system (1873 K). The results have been analysed using Apelian and Mutharasan's kinetic model for filtration of the metallic melts [1]. The inclusion capture kinetics and filtration characteristics of the porous media used in this investigation are discussed. 相似文献