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1.
Wettability of liquid A359 alloy on SiC particles under molten salt NaCl-KCl-NaF is found at 180 deg, meaning that SiC particles
prefer the molten salt phase against the Al phase or the Al/molten salt interface. Thus, this molten salt can be used for
recycling, i.e., to separate the phases in the SiC reinforced Al matrix composites. If the separation process is interrupted, Al droplets
(submillimeter solidified powder) can be produced, stabilized/surrounded by a monolayer of shielding SiC particles. 相似文献
2.
Wenquan Lu Shuguang Zhang Wei Zhang Qiaodan Hu Jianding Yu Yanan Fu Jianguo Li 《Metallurgical and Materials Transactions A》2017,48(6):2701-2705
Using synchrotron radiography, in this study, we caught a full view of the segregation evolution of Al–10 wt pct Bi immiscible alloy during solidification. We provide the direct experimental evidence of surface segregation prior to liquid decomposition. And the Bi enrichment at the bottom part should come from melt flow rather than Soret effect. The Marangoni effect and Stokes effect dominate in separate stages in solidifying Al–Bi alloy. Further, the size distribution of Bi droplets obeys Gaussian distribution. 相似文献
3.
采用伪半固态触变成形工艺制备了40%、56%和63%三种不同SiC体积分数颗粒增强Al基电子封装材料,并借助光学显微镜和扫描电镜分析了材料中Al和SiC的形态分布及其断口形貌,测定了材料的密度、致密度、热导率、热膨胀系数、抗压强度和抗弯强度.结果表明,通过伪半固态触变成形工艺可制备出的不同SiC体积分数Al基电子封装材料,其致密度高,热膨胀系数可控,材料中Al基体相互连接构成网状,SiC颗粒均匀镶嵌分布于Al基体中.随着SiC颗粒体积分数的增加,电子封装材料密度和室温下的热导率稍有增加,热膨胀系数逐渐减小,室温下的抗压强度和抗弯强度逐渐增加.SiC/Al电子封装材料的断裂方式为SiC的脆性断裂,同时伴随着Al基体的韧性断裂. 相似文献
4.
Yue Wu Jinmin Zhang Enrique J. Lavernia 《Metallurgical and Materials Transactions B》1994,25(1):135-147
In the present investigation, a theoretical model was developed to study the penetration behavior of ceramic particulates
into metallic droplets during spray atomization and coinjection. In formulating the penetration problem, a force balance approach
was adopted that considers the variations of both surface-tension resistance and fluid drag during the penetration processes.
Using this model, the factors that affect the penetration behavior of ceramic particulates into Al droplets were systematically
discussed. These include size, morphology, and density of ceramic paniculate; wetting angle between ceramic and liquid Al;
and fraction of solid contained in the semiliquid droplets. It was found that the critical velocity required for penetration
increased with increasing wetting angle and fraction of solid but decreased with increasing particulate density. The penetration
ability of various ceramic particulates was compared. It was found that the penetration ability of ceramic particulates that
are normally encountered in Albased metal matrix composites (MMCs) decreases in the following sequence: TiB2, Al2O3, SiC, and graphite. 相似文献
5.
The present study was undertaken to provide insight into the dynamic interactions that occur when ceramic particles are placed
in intimate contact with a metallic matrix undergoing a phase change. To that effect, Al-4 wt pct Si/SiCp composite droplets were synthesized using a spray atomization and coinjection approach, and their solidification microstructures
were studied both qualitatively and quantitatively. The present results show that SiC particles (SiCp) were incor- porated into the matrix and that the extent of incorporation depends on the solidification con- dition of the
droplets at the moment of SiC particle injection. Two factors were found to affect the distribution and volume fraction of
SiC particles in droplets: the penetration of particles into droplets and the entrapment and/or rejection of particles by
the solidification front. First, during coinjection, particles collide with the atomized droplets with three possible results:
they may penetrate the droplets, adhere to the droplet surface, or bounce back after impact. The extent of penetration of
SiC particles into droplets was noted to depend on the kinetic energy of the particles and the magnitude of the surface energy
change in the droplets that occurs upon impact. In liquid droplets, the extent of penetration of SiC particles was shown to
depend on the changes in surface energy, ΔEs, experienced by the droplets. Accordingly, large SiC particles encoun- tered more resistance to penetration relative to small
ones. In solid droplets, the penetration of SiC particles was correlated with the dynamic pressure exerted by the SiC particles
on the droplets during impact and the depth of the ensuing crater. The results showed that no pene- tration was possible in
such droplets. Second, once SiC particles have penetrated droplets, their final location in the microstructure is governed
by their interactions with the solidification front. As a result of these interactions, both entrapment and rejection of SiC
particles occurred during droplet solidification. A comparison of the present results to those anticipated from well-established
kinetic and thermodynamic models led to some interesting findings. First, the models proposed by Boiling and Cisse[24] and Chernovet al.[58] predict relative low critical interface velocities necessary for entrapment, inconsistent with the present experimental findings.
Second, although the observed correlation between the critical front velocity and droplet diameter was generally consistent
with that predicted by Stefanescuet a/.’s model,[27] the dependence on the size of SiC particles was not. In view of this discrepancy, three possible mechanisms were proposed
to account for the experimental findings: nucleation of α-Al on SiC particles, entrapment of SiC particles between primary
dendrite arms, and entrapment of SiC particles between secondary dendrite arms. 相似文献
6.
用电化学方法研究了 2 0 2 4Al和SiCP/2 0 2 4Al基复合材料在 3 5NaCl水溶液中的耐蚀性 ,用电化学阻抗技术对它们的硫酸阳极氧化膜的耐蚀性进行了研究 .结果表明 ,SiCP/2 0 2 4Al复合材料在3 5 %NaCl水溶液中比相应的基体金属有较大的腐蚀敏感性 .SiCP/2 0 2 4Al的阳极氧化膜具有良好的耐NaCl溶液腐蚀能力 ,但其耐蚀性不如 2 0 2 4Al合金的阳极氧化膜 ,这是由于氧化膜中SiC颗粒的存在破坏了氧化膜的完整性和均匀性所致 相似文献
7.
8.
研究了球磨过程中选用钢球、玛瑙球和氧化锆三种不同材质的磨球对SiC纳米颗粒在Al中分散性的影响。结果表明,在其它试验参数相同的情况下,用三种不同材质的磨球所获得的混合粉形态有很大差异。采用氧化锆磨球可以更好地使SiC纳米颗粒均匀分散在Al基体中,而用钢球和玛瑙球则易产生混合粉的团聚。对用氧化锆球进行球磨后的复合粉在773K的温度下加压100MPa热压烧结制得了组织成分均匀的块体纳米复合材料。其力学性能与同成分的普通复合材料相比有明显提高。 相似文献
9.
以铝粉、硅粉、石墨粉为原料, 通过冷压真空烧结原位合成了含不同质量分数SiC颗粒的SiC/Al-18Si复合材料。利用X射线衍射仪, 扫描电子显微镜和能谱分析仪等设备手段表征了铝基复合材料的相组成和微观结构, 研究了原位合成SiC对复合材料微观结构、抗弯强度和显微硬度的影响, 分析了复合材料力学性能的变化规律。结果表明: 复合材料的基体相为Al相, 第二相为Si相和SiC相; 原位合成的SiC颗粒弥散细小的分布在Al基体中, 其颗粒尺寸主要分布在0.2~2.8 μm, 具有亚微米、微米级的多尺度特性; 随着SiC质量分数的不断增加, 复合材料的显微硬度增大, 同时颗粒的平均尺寸仅由0.81 μm增大到1.13 μm, 但仍均匀分布, 正是这种尺寸稳定性, 使得SiC/Al-18Si复合材料硬度远大于Al-18Si; 当SiC质量分数为30%时, 材料的显微硬度最高, 达到HV 134, 相较于Al-18Si提高了88%。 相似文献
10.
A SiC particulate-reinforced 2024Al matrix composite was fabricated using a spray atomization and codeposition process to
produce a layered macrostructure. The thermal macro- and microresidual stresses that develop in this layered 2024Al/SiC composite
during cooling from the codeposition temperature to ambient temperature were studied using thermoelastoplastic finite element
analysis. The calculated residual stresses from finite element method were compared with those obtained from X-ray diffraction
(XRD), and good agreement was observed between them. The macroresidual stress distribution was very distinct for the Al and
the SiC-rich layers. The macroradial stress was tensile in the Al layers and compressive in the SiC-rich layers. The macroaxial
stress was found to be compressive in the vicinity of the center region of the spray-deposited material and to have mostly
a continuous distribution in the Al and the SiC-rich layers. The magnitude of the macroaxial stress was noted to decrease
with increasing deposition thickness from the bottom. In addition, the spray-deposited material exhibited the highest macro-von
Mises’ stress around the outer edge of the deposited material. The microradial stress was in a compressive state in the SiC
particulate and in the Al matrix in the vicinity of the SiC particulate. The SiC particulate exhibited compressive microhoop
stress, whereas the Al matrix exhibited tensile microhoop stress. The micro-von Mises’ stress was of the highest value at
the interface between the SiC particulate and the Al matrix. 相似文献
11.
I. Manivannan S. Ranganathan S. Gopalakannan S. Suresh 《Transactions of the Indian Institute of Metals》2018,71(8):1897-1911
In the present investigation, a newly fabricated Al6061 reinforced with various quantity (0.4–1.6 wt%) of nano SiC in steps of 0.4 and fixed quantity (0.5 wt%) of micro graphite particle’s hybrid nanocomposites were prepared by ultrasonic assisted stir casting method. The influence of nano SiC and graphite content on the mechanical and tribological properties of Al6061 hybrid nanocomposites were studied. The pin-on-disc equipment was used to carry out experiment at 10–40 N applied load, 0.5 m/s sliding speed and 1000 m sliding distance. The Al/SiC/Gr hybrid nano-composite and matrix alloy wear surfaces were characterized by FESEM equipped with an EDS, 3D profilometer to understand the wear mechanisms. The results of Al/SiC/Gr self-lubricating hybrid nano-composites showed improved wear resistance than the Al6061 matrix alloy. The co-efficient of friction of Al/SiC/Gr hybrid nano-composites were lower than those of the unreinforced alloy at various applied load. Compared to matrix alloy, the surface roughness of Al/SiC/Gr hybrid nano-composites had significantly reduced to 66% at low load and 75% at high load. Self-lubricating Al/SiC/Gr hybrid nanocomposites showed superior surface smoothness compared to matrix alloy. 相似文献
12.
A simple method of metal foam production is to introduce a blowing agent (e.g. TiH2) into an aluminium melt containing foam stabilisers such as oxides (usually Ca-based) and/or particles (e.g. SiC, Al2O3). In this work, Al/SiC composites (in-house and commercial Duralcan) [both of them with LM25 matrix (Al?C7Si?C0.3Mg)] containing particles of various sizes and contents were foamed at different temperatures using TiH2. Foamability is characterised through their expansion and collapse. It is observed that high expansions and good quality foams could be obtained upon manipulating SiC particle size and content. However, irrespective of particle size/vol.% combination, significant effect of foaming temperature is noticed on the fundamental stability of the liquid foam until solidification. Both cell size and foam density varied along the ingot height. The distribution of SiCP within the cell wall is random with no preferential segregation to gas/metal interface. The evolution of foam, and the role of SiC on foam stability are discussed based on macro and cell wall microstructural results. 相似文献
13.
《Acta Metallurgica Materialia》1994,42(9):2955-2971
The present study provides insight into the physical interactions that take place when an injected ceramic particulate collides with an atomized metallic droplet during spray atomization and deposition processing of particulate reinforced metal matrix composites. A model is developed to predict the extent of penetration for a given particulate velocity, and the critical velocity for complete penetration. In the model, the initial kinetic energy of the injected particulates or the atomized droplets is considered as the driving force for penetration; the change in surface energies and the work done by viscous drag in the droplet melt are considered as the forces resisting penetration. As examples, Al/graphite and Al/SiC systems are analyzed to demonstrate the applicability of the model. The influence of the particulate size and the fraction of solid phase in the atomized droplet on the critical velocity and the penetration depth is also examined. 相似文献
14.
15.
Melt-spun Al-3 wt pct Si with and without ternary additions of Na and Sr has been heat-treated above the Al-Si eutectic temperature
in a differential scanning calorimeter to form a microstructure of Al-Si eutectic liquid droplets embedded in the α-Al matrix.
During subsequent cooling in the calorimeter, the heterogeneous nucleation temperature for solidification of Si in contact
with the surrounding Al matrix depends sensitively on the alloy purity, with a nucleation undercooling which increases with
increasing alloy purity from 9 to 63 K below the Al-Si eutectic temperature. These results are consistent with Southin’s hypothesis
that low levels of trace P impurities are effective in catalyzing Si nucleation in contact with the surrounding Al matrix.
With a low Al purity alloy, 0.1 wt pct Na addition increases the Si nucleation undercooling from 9 to 50 K, 0.15 wt pct Sr
addition does not affect the Si nucleation temperature, and 0.3 wt pct Sr addition decreases the Si nucleation undercooling
from 9 to 3 to 4 K. The solidified microstructure of the liquid Al-Si eutectic droplets embedded in the Al matrix depends
on the Si nucleation undercooling. With low Si nucleation undercooling, each Al-Si eutectic liquid droplet solidifies to form
one faceted Si particle; however, with high Si nucleation undercooling, each Al-Si eutectic droplet solidifies to form a large
number of nonfaceted Si particles embedded in Al.
Formerly with the Oxford Centre for Advanced Materials and Composites, Department of Materials, Oxford University 相似文献
16.
采用粉末冶金法制备SiC颗粒增强工业纯Al基复合材料,研究混料时间和挤压对复合材料显微组织和力学性能的影响。研究表明:机械混粉过程存在最佳的混料时间,混料时间为16 h时SiC颗粒分布均匀,复合材料的密度高、力学性能好。挤压可以改善复合材料的界面结合强度、减少孔洞的数量,从而提高材料的致密度和力学性能。烧结态复合材料的断裂机制以基体的脆性断裂以及增强相与基体的界面脱粘为主。挤压态复合材料的断裂以基体的韧性断裂以及SiC颗粒的脆性断裂为主,伴随着少量的基体与SiC颗粒的界面脱粘。 相似文献
17.
18.
Ali Mazahery Mehdi Alizadeh Mohsen Ostad Shabani 《Transactions of the Indian Institute of Metals》2012,65(4):393-398
In the present investigation, the microstructural, wear, tensile and compressive properties of Al?C7Si alloy matrix nano composites have been discussed. It is noted that the composites contain higher porosity level in comparison to the matrix and increasing amount of porosity is observed with the increasing volume fraction of the reinforcement phase in the matrix. The wear sliding test disclosed that the wear resistance of the nano SiC reinforced composites is higher than that of the unreinforced alloy. It is believed that the presence of SiC particles could shield the matrix and silicon phase from directly experiencing the applied load from the counterface. It was revealed that the presence of nano-SiC reinforcement also enhanced the hardness, tensile and compressive yield strength of Al?C7Si alloy which can be attributed to small particle size and good distribution of the SiC particles and grain refinement of the matrix. The highest yield strength and UTS was obtained by the composite with 3.5?vol% SiC nano-particles. The results show that the addition of nano-particles reduces the elongation of A356 alloy. 相似文献
19.
Russian Journal of Non-Ferrous Metals - In this study, the micro-mechanisms involved in fatigue crack propagation are investigated qualitatively in a Al/Al2O3/SiC hybrid metal matrix composite... 相似文献
20.
Wear tests on SiC whisker- and SiC particulate-reinforced 6061-T6 aluminum matrix composites (SiCw/Al and SiCp/Al), fabricated
using a high pressure infiltration method, were performed in laboratory air, ion-exchanged water and a 3 pct NaCl aqueous
solution using a block-on-ring type apparatus. The effects of environment, applied load, and rotational (sliding) speed on
the wear prop-erties against a sintered alumina block were evaluated. Electrochemical measurements in ion-ex-changed water
and a 3 pct NaCl aqueous solution were also made under the same conditions as the wear tests. A comparison was made with the
properties of the matrix aluminum alloy 6061-T6. The SiC-reinforced composites exhibited better wear resistance compared with
the monolithic 6061 Al alloy even in a 3 pct NaCl aqueous solution. Increase in the wear resistance depended on the shape,
size, and volume fraction of the SiC reinforcement. Good correlation was obtained between corrosion resistance and corrosion
wear. The ratios of wear volume due to the corrosive effect to noncorrosive wear were 23 to 83 pct, depending on the wear
conditions. 相似文献