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1.
Yu-Fu Liu Yoshihisa Tanaka Chitoshi Masuda 《Metallurgical and Materials Transactions A》2000,31(10):2637-2645
Direct observation of initial damage-evolution processes occurring during cyclic testing of an unnotched SCS-6 fiber-reinforced
Ti-15-3 composite has been carried out. The aligned fibers break at an early stage, followed by debonding and subsequent sliding
along the interface between the reaction layer (RL) and Ti-15-3 alloy matrix. Matrix cracking initiation from the initial
broken fiber and RL was avoided. This fracture behavior during cyclic loading is modeled and analyzed by the finite-element
method, with plastic deformation of the matrix being considered. The plastic strain in the matrix at the initial crack and
at the deflected crack tips, when the interface crack is deflected into the RL after extensive interface debonding propagation,
is characterized. The effects of interfacial debond lengths and test temperatures on the matrix cracking mechanism are discussed,
based on a fatigue-damage summation rule under low-cycle fatigue conditions. The numerical results provide a rationale for
experimental observations regarding the avoidance and occurrence of the matrix cracking found in fiber-reinforced titanium
composites. 相似文献
2.
Y. Tanaka C. Masuda Y. -F. Liu Y. Kagawa S. Q. Guo 《Metallurgical and Materials Transactions A》1999,30(1):221-229
Unnotched SiC (SCS-6) fiber-reinforced Ti-15-3 alloy composite is subjected to a tension-tension fatigue test in a vacuum
of 2×10−3 Pa at 293 and 823 K with a frequency of 2 Hz and R=0.1. Direct observation of the damage evolution process during the test is carried out by scanning electron microscopy (SEM).
Test temperature dependent and independent fatigue damage behaviors are observed. The early stage fiber fractures observed
at the polished surface are not influenced by the test temperature; however, matrix crack initiation and propagation behaviors
differ greatly with temperature. The evolution of interface wear damage also differs with temperature, becoming more severe
at 823 K, and the interface wear damage zone increases with the increase of the number of fatigue cycles. The macroscopic
fatigue damage appears as a modulus reduction associated with interface sliding, matrix crack propagation, and plastic deformation
of the matrix. The deformation zone of the composite tested at 823 K spreads more than that at 293 K. The fatigue life of
the composite tested at 823 K is longer than that at 293 K. This behavior is related to the difference in spread of the damage
zone in the matrix. 相似文献
3.
O. Jin Y. Li B. M. Rabeeh W. O. Soboyejo 《Metallurgical and Materials Transactions A》1997,28(12):2583-2593
The effects of interfacial microstructure/thickness on the strength and fatigue behavior of a model four-ply [75]4 Ti-15V-3Al-3Cr-3Sn/SiC (SCS-6) composite are examined in this article. Interfacial microstructure was controlled by annealing
at 815 °C for 10, 50, or 100 hours. The reaction layer and coating thickness were observed to increase with increasing annealing
duration. Damage initiation/propagation mechanisms were examined in as-received material and composites annealed at 815 °C
for 10 and 100 hours. Fatigue behavior was observed to be dependent upon the stress amplitude. At high stress amplitudes,
the failure was dominated by overload phenomena. However, at all stress levels, fatigue crack initiation occurred by early
debonding and matrix deformation by stress-induced precipitation. This was followed by matrix crack growth and fiber fracture
prior to the onset of catastrophic failure. Matrix shear failure modes were also observed on the fracture surfaces in addition
to fatigue striations in the matrix. Correlations were also established between the observed damage modes and acoustic emission
signals that were detected under monotonic and cyclic loading conditions. 相似文献
4.
The transverse behavior of 1140+/Ti-6-4 and SCS-6/Ti-β21s composites has been investigated using conventional tensile testing in air. Acoustic emission (AE) has also been used to
assess and to locate the position of damage. Few AE events can be detected in 1140+/Ti-6-4 composites below the stress of
∼250 MPa, whereas for SCS-6/Ti-β21s composites, AE events are found almost immediately on loading. Many AE events of high energy were detected over a range of
stresses, which appear to be associated with debonding. Continuous AE events are obtained with an increase of stress, and
this suggests that debonding is an incremental process: a ring crack (formed by premature debonding at the surface) penetrates
into the depth along interface “tubes.” The peak energy of AE events obtained in SCS-6/Ti-β21s composites is ∼650 arbitrary units, which is approximately 4 times that obtained in 1140+/Ti-6-4 composites. Distinct AE
events have also been deduced to correspond to cracking of carbon coating layers and fiber/matrix reaction products. A change
of fiber volume fraction from 8 to 21 pct for the 1140+/Ti-6-4 composites has no effect on the characteristics or distribution
of AE events received. 相似文献
5.
S. G. Warrier S. H. Chen S. K. Wu R. Y. Lin 《Metallurgical and Materials Transactions A》1996,27(5):1379-1394
Interfacial reactions between several ceramic fibers (SCS-0, SCS-6, and carbon fibers) and a liquid titanium-nickel-copper
alloy were investigated using electron microscopic analysis. Composite spec-imens were produced using a rapid infrared manufacturing
(RIM) process. In SCS-O/Ti alloy com-posites, SiC dissolved in the alloy. The main reaction product was discontinuous agglomerates
of titanium carbide which formed from the reaction between dissolved carbon and titanium. Polygonal precipitates of Ti5Si3, which are believed to have formed during cooling, were also noticed. Two distinct interface morphologies were observed in
these composites: uniform fronts caused by iso-thermal dissolution and scalloped fronts formed as a result of an accelerated
dissolution mechanism caused by localized heating. The presence of the accelerated dissolution mechanism suggests that SiC
fibers cannot be infiltrated with liquid titanium alloys without applying a coating. In the C/Ti system, carbon fibers reacted
with the liquid alloy to form a continuous layer of TixC1-x. Further growth of this layer occurred by the diffusion of carbon atoms across the reaction product. In SCS-6/Ti alloy composites,
free carbon present in the coating formed a discontinuous layer of Ti^C,^, whereas SiC particles dissolved in the alloy. Due
to channeled dissolution in the coating, the accel-erated dissolution mechanism was not observed in these composites. As a
result, the presence of the carbon-rich coating prevented degradation of the fibers. Although the coating present on SCS-6
fibers moderately retarded reactions in the SiC/Ti alloy composite system during infrared liquid infiltration, it is recommended
that the fibers be coated with pure carbon to effectively limit the attack of the fiber by molten titanium.
Formaly Postdoctoral Fellow, Department of Materials Science and Engineering, University of Cincinnati 相似文献
6.
While continuous fiber, unidirectional composites are primarily evaluated for their longitudinal properties, the behavior
transverse to the fibers often limits their application. In this study, the tensile and creep behaviors of SCS-6/Ti-6Al-4V
composites in the transverse direction at 482 °C were evaluated. Creep tests were performed in air and argon environments
over the stress range of 103 to 276 MPa. The composite was less creep resistant than the matrix when tested at stress values
larger than 150 MPa. Below 150 MPa, the composite was more creep resistant than the unreinforced matrix. Failure of the composite
occurred by the ductile propagation of cracks emanating from separated fiber interfaces. The environment in which the test
was performed affected the creep behavior. At 103 MPa, the creep rate in argon was 4 times slower than the creep rate in air.
The SCS-6 silicon-carbide fiber’s graphite coating oxidized in the air environment and encouraged the separation of the fiber-matrix
interface. However, at higher stress levels, the difference in behavior between air- and argon-tested specimens was small.
At these stresses, separation of the interface occurred during the initial loading of the composite and the subsequent degradation
of the interface did not affect the creep behavior. Finally, the enrichment of the composite’s surface by molybdenum during
fabrication resulted in an alloyed surface layer that failed in a brittle fashion during specimen elongation. Although this
embrittled layer did not appear to degrade the properties of the composite, the existence of a similar layer on a composite
with a more brittle matrix might be very detrimental. 相似文献
7.
P. Rangaswamy M. A. M. Bourke R. Von Dreele K. Bennett M. R. Daymond N. Jayaraman 《Metallurgical and Materials Transactions A》2000,31(3):889-898
Residual strain and texture variations were measured in two titanium matrix composites reinforced with silicon carbide fibers
(Ti/SiC) of similar composition but fabricated by different processing routes. Each composite comprised a Ti-6242 α/β matrix alloy containing vol 35 pct continuous SiC fibers. In one, the matrix was produced by a plasma sprayed (PS) route,
and in the other by a wiredrawn (WD) process. The PS and WD composites were reinforced with SCS-6 (SiC) and Trimarc (SiC)
fibers, respectively. The texture in the titanium matrices differed significantly. The titanium matrix for the PS material
exhibited random texture pre and post fabrication of the composite. For the WD material, the starting texture of the monolithic
titanium matrix was ≈17 times random, but after consolidation into composite form, it was ≈6 times random. No significant
differences were noted in the fiber-induced matrix residual strains between the composites prepared by the two procedures.
However, the Trimarc (WD) fibers recorded higher (≈1.3 times) compressive strains than the SCS-6 (PS) fibers. Stresses and
stress balance results are reported. Plane-specific elastic moduli, measured in load tests on the unreinforced matrices, showed
little difference.
This article is based on a presentation made in the Symposium “Mechanisms and Mechanics of Composites Fracture” held October
11–15, 1998, at the TMS Fall Meeting in Rosemont, Illinois, under the auspices of the TMS-SMD/ASM-MSCTS Composite Materials
Committee. 相似文献
8.
Nikhilesh Chawla 《Metallurgical and Materials Transactions A》1997,28(11):2423-2427
In many potential applications, continuous fiber-reinforced ceramic matrix composites (CFCMCs) will encounter cyclic fatigue
loadings at high frequencies (25 Hz or higher). While most of the work in the area of fatigue of CFCMCs has concentrated on
low frequency behavior, high frequency behavior is equally important. In CFCMCs, stress-strain hysteresis occurs during fatigue
and is associated with energy dissipation in the composite. In addition to this, the repeated friction and sliding between
fiber and matrix are responsible for a substantial temperature rise at the fiber/matrix interface. In this study, [0/90] and
[±45] SCS-6 (silicon carbide)/Si3N4 composites made by hot pressing were investigated under high frequency fatigue loadings. The angle-ply laminate showed the
same extent of heating as cross-ply laminates, but at much lower stress levels. Frictional heating was caused by sliding at
the fiber/matrix interface. Temperature rise due to heat generation in the specimens correlated very well with damage in modulus
as a function of fatigue cycles in the composites. Matrix microcracking was more predominant in the angle ply than in the
cross-ply composite, due to the much lower stiffness of the angle-ply composite in the longitudinal loading direction. 相似文献
9.
S. G. Warrier D. B. Gundel B. S. Majumdar D. B. Miracle 《Metallurgical and Materials Transactions A》1996,27(7):2035-2043
The ability of a fiber-matrix interface to support a transverse load is typically evaluated in straight-sided composite specimens
where a stress singularity exists at the free surface of the interface. This stress singularity is often the cause of crack
initiation and debonding during transverse loading. In order to develop a fundamental understanding of the transverse behavior
of the fiber-matrix interface, it is necessary to alter the crack initiation site from the free surface to an internal location.
To achieve this objective, a cross-shaped specimen has been recently developed. In this study, based on the experimentally
observed onset of nonlinearity in the stress-strain curve of these specimens and finite element analysis, the bond strength
of the SCS-6/Ti-6Al-4V interface was determined to be 115 MPa. The micromechanical behavior of these specimens under transverse
loading was examined by finite element analysis using this interface bond strength value and compared with experimental observations.
Results demonstrate that the proposed geometry was successful in suppressing de-bonding at the surface and altering it to
an internal event. The results from numerical analysis correlated well with the experimental stress-strain curve and several
simple analytical models. In an attempt to identify the true bond strength and the interface failure criterion, the present
study suggests that if failure initiates under tensile radial stresses, then the normal bond strength of the SCS-6/Ti-6A1-4V
composites is about 115 MPa; under shear failure, the tangential shear strength of the in-terface is about 180 MPa. 相似文献
10.
P. Rangaswamy M. R. Daymond M. A. M. Bourke R. Von Dreele K. Bennett N. Jayaraman 《Metallurgical and Materials Transactions A》2000,31(13):889-898
Residual strain and texture variations were measured in two titanium matrix composites reinforced with silicon carbide fibers
(Ti/SiC) of similar composition but fabricated by different processing routes. Each composite comprised a Ti-6242 α/β matrix
alloy containing vol 35 pct continuous SiC fibers. In one, the matrix was produced by a plasma sprayed (PS) route, and in
the other by a wiredrawn (WD) process. The PS and WD composites were reinforced with SCS-6 (SiC) and Trimarc (SiC) fibers,
respectively. The texture in the titanium matrices differed significantly. The titanium matrix for the PS material exhibited
random texture pre and post fabrication of the composite. For the WD material, the starting texture of the monolithic titanium
matrix was ≈17 times random, but after consolidation into composite form, it was ≈6 times random. No significant differences
were noted in the fiber-induced matrix residual strains between the composites prepared by the two procedures. However, the
Trimarc (WD) fibers recorded higher (≈1.3 times) compressive strains than the SCS-6 (PS) fibers. Stresses and stress balance
results are reported. Plane-specific elastic moduli, measured in load tests on the unreinforced matrices, showed little difference.
This article is based on a presentation made in the Symposium “Mechanisms and Mechanics of Composites Fracture” held October
11–15, 1998, at the TMS Fall Meeting in Rosemont, Illinois, under the auspices of the TMS-SMD/ASM-MSCTS Composite Materials
Committee. 相似文献
11.
James M. Larsen Stephan M. Russ J. W. Jones 《Metallurgical and Materials Transactions A》1995,26(12):3211-3223
The current capabilities of continuous silicon-carbide fiber-reinforced titanium matrix composites (TMCs) are reviewed with
respect to application needs and compared to the capabilities of conventional high-temperature monolithic alloys and aluminides.
In particular, the properties of a firstgeneration titanium aluminide composite, SCS-6/Ti-24Al-11Nb, and a second-generation
metastable beta alloy composite, SCS-6/TIMETAL 21S, are compared with the nickel-base superalloy IN100, the high-temperature
titanium alloy Ti-1100, and a relatively new titanium aluminide alloy. Emphasis is given to life-limiting cyclic and monotonie
properties and to the influence of time-dependent deformation and environmental effects on these properties. The composite
materials offer a wide range of performance capabilities, depending on laminate architecture. In many instances, unidirectional
composites exhibit outstanding properties, although the same materials loaded transverse to the fiber direction typically
exhibit very poor properties, primarily due to the weak fiber/matrix interface. Depending on the specific mechanical property
under consideration, composite cross-ply laminates often show no improvement over the capability of conventional monolithic
materials. Thus, it is essential that these composite materials be tailored to achieve a balance of properties suitable to
the specific application needs if these materials are to be attractive candidates to replace more conventional materials.
This article is based on a presentation made in the symposium entitled “Creep and Fatigue in Metal Matrix Composites” at the
1994 TMS/ASM Spring meeting, held February 28–March 3, 1994, in San Francisco, California, under the auspices of the Joint
TMS-SMD/ASM-MSD Composite Materials Committee. 相似文献
12.
Rebecca A. Mackay Susan L. Draper Ann M. Ritter Paul A. Siemers 《Metallurgical and Materials Transactions A》1994,25(7):1443-1455
The tensile properties of SCS-6 SiC fiber-reinforced Ti-24Al-11Nb (at. pct) have been measured over the past several years
by a number of investigators. These composites have been fabricated by different techniques and tend to exhibit a large amount
of scatter in the longitudinal tensile properties. To date, it is not known if one optimized fabrication method provides composites
with improved mechanical properties over those produced by other optimized methods, since carefully controlled experiments
have not been performed to determine this. Thus, the purpose of the present study was to compare the longitudinal tensile
strengths of SCS-6 SiC/ Ti-24Al-11Nb composites that had been fabricated by the powder-cloth method and the lowpressure plasma
spray (LPPS) method. In this study, the same lots of matrix powder and reinforcing fiber were used for fabricating the composites.
It was determined that the powder-cloth and plasma spray methods produced composites having very similar tensile properties.
Both fabrication methods induced damage in a small percentage of fibers, which manifested itself in the form of bimodal Weibull
distributions of extracted fiber strengths. It appeared that the particular lot of SCS-6 fiber used in fabricating both types
of composites was more susceptible to fabrication damage than those used in previous studies. This article also shows the
dramatic effect that different handling and testing techniques can have on measured fiber strengths. 相似文献
13.
The transverse stress-strain behavior of several titanium metal-matrix composites (TiMMCs) has been studied in-situ. Debonding of 1140+/Ti-6-4 composites occurs over a range of stresses. The sharpness of the first “knee” is affected by the
fiber volume fraction and by the relative moduli of the matrix regions and the reinforced composite. It has been observed
that debonding occurs mainly at the interface between two sublayers of carbon/carbon coatings in 1140+/Ti-6-4 composites and
mainly at the interface between the carbon/reaction zone in the as-processed and peak-aged 35 pct SCS-6/Tiβ21s composites. At surface positions, this process starts at very low stresses (≥50 MPa) from the positions with sharp changes
of curvatures (or undulations), voids, or debris at the periphery of the interface. Cracking of the outermost carbon sublayer
and of the reaction zone in the 1140+/Ti-6-4 composites and the reaction zone in the SCS-6/Tiβ21s composites occurs during elastic deformation of the matrix. This has been directly observed in a field-emission gun (FEG)-scanning
electron microscope (SEM) under incremental loading. Although these cracks are arrested and blunted by the matrix material,
they cause local stresses and, thus, stimulate local plastic deformation of the matrix and subsequent development of a second
knee on the stress-strain curve. The in-situ observations are discussed in terms of the effects of fiber volume fraction and fiber type on the loci and dynamic processes
of interfacial debonding, cracking of carbon coatings and reaction zones, and plastic deformation of the matrix. 相似文献
14.
P. K. Liaw E. S. Diaz K. T. Chiang D. H. Loh 《Metallurgical and Materials Transactions A》1995,26(12):3225-3247
Flexural fatigue behavior was investigated on titanium (Ti-15V-3Cr) metal matrix composites reinforced with cross-ply, continuous
silicon carbide (SiC) fibers. The titanium composites had an eightply (0, 90, +45, -45 deg) symmetric layup. Fatigue life
was found to be sensitive to fiber layup sequence. Increasing the test temperature from 24 °C to 427 °C decreased fatigue
life. Interface debonding and matrix and fiber fracture were characteristic of tensile behavior regardless of test temperature.
In the tensile fracture process, interface debonding between SiC and the graphite coating and between the graphite coating
and the carbon core could occur. A greater amount of coating degradation at 427 °C than at 24 °C reduced the Ti/SiC interface
bonding integrity, which resulted in lower tensile properties at 427 °C. During tensile testing, a crack could initiate from
the debonded Ti/SiC interface and extend to the debonded interface of the neighboring fiber. The crack tended to propagate
through the matrix and the interface. Dimpled fracture was the prime mode of matrix fracture. During fatigue testing, four
stages of flexural deflection behavior were observed. The deflection at stage I increased slightly with fatigue cycling, while
that at stage II increased significantly with cycling. Interestingly, the deflection at stage III increased negligibly with
fatigue cycling. Stage IV was associated with final failure, and the deflection increased abruptly. Interface debonding, matrix
cracking, and fiber bridging were identified as the prime modes of fatigue mechanisms. To a lesser extent, fiber fracture
was observed during fatigue. However, fiber fracture was believed to occur near the final stage of fatigue failure. In fatigued
specimens, facet-type fracture appearance was characteristic of matrix fracture morphology. Theoretical modeling of the fatigue
behavior of Ti/SCS-6 composites is presented in Part II of this series of articles.
This article is based on a presentation made in the symposium entitled “Creep and Fatigue in Metal Matrix Composites” at the
1994 TMS/ASM Spring meeting, held February 28–March 3, 1994, in San Francisco, California, under the auspices of the Joint
TMS-SMD/ASM-MSD Composite Materials Committee. 相似文献
15.
《Acta Metallurgica Materialia》1995,43(4):1477-1487
The interfacial shear stress distribution of a thin specimen of SiC fiber-reinforced glass matrix composite (fiber volume fraction of 0.1, 0.5 and 0.7) during a fiber pushout process was subjected to finite element analysis using a three concentric axisymmetrical model which consisted of fiber, matrix, and composite. A stress criterion was used to determine interface debonding. Effects of thermally-induced stress and a post debond sliding process at the interface were also included in the analysis. The analytical result showed that shear stress near the specimen surface was introduced during the specimen preparation process. Before the interfacial debonding, the distribution of shear stress during the pushout test was affected by the existence of thermally-induced stress in the specimen. The interfacial shear debonding initiated ≈ 30 μm below the pushing surface and the sliding at the debonded interface proceeded in the direction of both the pushing surface and back surface from the peak shear position; the debonding from the back surface initiated just before the complete debonding of the interface. The pushout load-displacement curve near the origin was straight, however, after the existence of interface sliding at the debonded interface, the curve exhibited non-linearity with the increase in applied load up to the complete debonding at the interface. This debonding process was essentially independent of the fiber volume fraction. The results indicate that the total of thermally-induced stress in the specimen and shear stress distribution generated by applied load are important for the initiation of debonding and the frictional sliding process of the thin specimen pushout test. 相似文献
16.
W. O. Soboyejo Y. Li S. I. Rokhlin B. M. Rabeeh Y. C. Chu A. Lavrentenyev 《Metallurgical and Materials Transactions A》1997,28(8):1667-1687
The results of a systematic study of the effects of microstructure on the strength and fatigue behavior of a symmetric [0/90]2s Ti-15Al-3Cr-3Al-3Sn/SiC (SCS-6) composite are presented along with relevant information on failnure mechanisms in the composite
constituents, i.e., the interface, fiber, and matrix materials. Damage micromechanisms are elucidated via optical microscopy, scanning electron microscopy (SEM), and nondestructive acoustic emission (AE) and ultrasonic techniques.
Composite damage is shown to initiate early under cyclic loading conditions and is dominated by longitudinal and transverse
interfacial cracking. Subsequent fatigue damage occurs by matrix slip band formation, matrix and fiber cracking, and crack
coalescence, prior to the onset of catastrophic failure. However, the sequence of the damage is different in material annealed
above or below the β solvus of the Ti-15-3 matrix material. Mechanistically based micromechanics models are applied to the
prediction of the changes in modulus induced by fatigue damage. Idealized fracture mechanics models are also employed in the
prediction of the fatigue lives of smooth specimens deformed to failure at room temperature. The article highlights the potential
to develop mechanistically based predictive models based on simplified mechanics idealizations of experimental observations. 相似文献
17.
C G. Rhodes A. K. Ghosh R. A. Spurling 《Metallurgical and Materials Transactions A》1987,18(12):2151-2156
Ti-6Al-4V-2Ni is being considered as a composite matrix material because of its potential for a lower consolidation temperature
and reduced reaction product formation compared with conventional Ti-6A1-4V. Stress/strain-rate measurements of Ti-6Al-4V-2Ni
in sheet form provided data for calculation of diffusion bonding parameters required for efficient consolidation. These data
were used as consolidation parameters for fabrication of SiC (SCS-6) reinforced Ti-6Al-4V-2Ni. The composite with 10.5 vol
pct SiC exhibits room temperature tensile strength approximately 80 pct of that observed for conventional Ti-6Al-4V/SiC having
35 to 40 vol pct SiC. Scanning and transmission electron microscopy revealed that the fiber-matrix reaction zone is roughly
one-half the thickness of that found in SiC-reinforced Ti -6A1-4V, and that it consists of TiC and Ti5Si3. Nickel does not enter into the reaction zone products, but rather promotes the formation of Ti2Ni in the matrix. 相似文献
18.
The effect of aging at elevated temperature on interfacial stability and fatigue behavior of a SCS-6/Ti-22Al-23Nb “orthorhombic”
(O) titanium aluminide composite is investigated. The composite was heat treated in vacuum at 900 °C for up to 250 hours to
change the microstructural characteristics. The stability of the matrix alloy and interfacial reaction zone after extended
thermal exposure was analyzed. The effect of interface on fatigue behavior, including stiffness degradation, evolution of
fatigue damage, and crack growth rates, was characterized. Finally, a modified shear-lag model was used to predict the saturated
matrix crack spacing in the composite under fatigue loading. The results demonstrate that aging at elevated temperature affects
the stability of the interfacial reaction zone, which, in turn, degrades the fatigue properties of the composite. However,
fatigue crack will not develop from the ruptured interfacial reaction layer until the thickness of the reaction zone or the
maximum applied stress exceeds a critical value. 相似文献
19.
为满足现代电子工业日益增长的散热需求,急需研究和开发新型高导热陶瓷(玻璃)基复合材料,而改善复合材料中增强相与基体的界面结合状况是提高复合材料热导率的重要途径.本文在对金刚石和镀Cr金刚石进行镀Cu和控制氧化的基础上,利用放电等离子烧结方法制备了不同的金刚石增强玻璃基复合材料,并观察了其微观形貌和界面结合状况,测定了复合材料的热导率.实验结果表明:复合材料中金刚石颗粒均匀分布于玻璃基体中,Cu/金刚石界面和Cr/Cu界面分别是两种复合材料中结合最弱的界面;复合材料的热导率随着金刚石体积分数的增加而增加;金刚石/玻璃复合材料的热导率随着镀Cu层厚度的增加而降低,由于镀Cr层实现了与金刚石的化学结合以及Cr在Cu层中的扩散,镀Cr金刚石/玻璃复合材料的热导率随着镀Cu层厚度的增加而增加.当金刚石粒径为100μm、体积分数为70%及镀Cu层厚度为约1.59μm时,复合材料的热导率最高达到约91.0 W·m-1·K-1. 相似文献
20.
通过盐浴镀覆在石墨鳞片表面镀铬,随后采用真空热压烧结技术制备了镀铬石墨鳞片/铜复合材料,研究了铬镀层的表面形貌和物相组成,并分析了铬镀层对石墨鳞片/铜复合材料显微结构和性能的影响。结果表明,盐浴镀铬层主要由Cr3C2和Cr7C3组成,经热压烧结后Cr7C3与石墨反应生成了Cr3C2;石墨鳞片表面镀铬可以明显减少石墨鳞片/铜复合材料界面处的孔隙,提高复合材料的热导率和抗弯强度,与未镀覆的复合材料相比,当镀铬石墨鳞片的体积分数为60%时,复合材料平面热导率相从594 W·m-1·K-1提高至625 W·m-1·K-1,抗弯强度提升65%。 相似文献