共查询到20条相似文献,搜索用时 46 毫秒
1.
J. S. Marte T. F. Zahrah S. L. Kampe 《Metallurgical and Materials Transactions A》2004,35(5):1603-1611
A series of in-situ, deformation-processed metal matrix composites were produced by direct powder extrusion of blended constituents. The resulting
composites are comprised of a metallic Ti-6Al-4V matrix containing dispersed and co-deformed discontinuously reinforced-intermetallic
matrix composite (DR-IMC) reinforcements. The DR-IMCs are comprised of discontinuous TiB2 particulate within a titanium trialuminide or near-γ Ti-47Al matrix. Thus, an example of a resulting composite would be Ti-6Al-4V+40 vol pct (Al3Ti+30 vol pct TiB2) or Ti-6Al-4V+40 vol pct (Ti-47Al+40 vol pct TiB2), with the DR-IMCs having an aligned, high aspect ratio morphology as a consequence of deformation processing. The degree
to which both constituents deform during extrusion has been examined using systematic variations in the percentage of TiB2 within the DR-IMC, and by varying the percentage of DR-IMC within the metal matrix. In the former instance, variation of
the TiB2 percentage effects variations in relative flow behavior; while in the latter, varying the percentage of DR-IMC within the
metallic matrix effects changes in strain distribution among components. The results indicate that successful co-deformation
processing can occur within certain ranges of relative flow stress; however, the extent of commensurate flow will be limited
by the constituents’ inherent capacity to plastically deform. 相似文献
2.
David L. Davidson 《Metallurgical and Materials Transactions A》1997,28(6):1297-1314
Fatigue cracks were grown through several niobium-based materials. For Nb-Cr-Ti composition materials, the single-phase alloy
represented the matrix of two in situ composites with about 22 and 38 vol pct Cr2Nb. Grain boundaries were coated with intermetallic in the lower-volume fraction material, while the 38 vol pct Cr2Nb composite consisted of mainly spherical, dispersed intermetallic. The Nb-10Si composite was composed of about 28 vol pct
primary Nb5Si3, with most of the matrix alloy in “fiberlike” shapes due to extrusion. Crack growth rates through the composites were generally
faster than for unalloyed Nb, roughly in proportion to the volume fraction of intermetallic, although differences in microstructure
make this comparison difficult. The presence of intermetallic greatly alters deformation of material near the crack tip. Particles
of Cr2Nb were broken during the crack growth process, leading to increased crack growth rates. These results suggest microstructural
modifications that could be expected to enhance fatigue crack growth resistance. 相似文献
3.
S. L. Kampe P. Sadler L. Christodoulou D. E. Larsen 《Metallurgical and Materials Transactions A》1994,25(10):2181-2197
A series of TiB2-reinforced near-γ titanium aluminide (Ti-Al) matrix composites have been produced in investment-cast form and characterized with respect to
microstructure and tensile deformation. The Ti-Al matrices of the composites examined are based upon the binary composition
Ti-47 Al (at. pct), with varying proportions (2 to 6 cumulative percent) of manganese, vanadium, chromium, and niobium. TiB2 has been introduced into the microstructuresvia XD* processing at levels of 7 and 12 vol pct and compared to unreinforced (0 vol pct TiB2), base variants. The influences of heat-treatment temperature and time have also been studied for each composition and reinforcement
variant. The addition of dispersed TiB2 leads to a fine, stable, and homogeneous as-cast matrix microstructure. The measured TiB2 size within the composites examined ranged from 1.4 to 2.6 μm. Increasing the volume fraction of TiB2 leads to increased elastic moduli, increased ambient temperature tensile strengths, and in general, increased strain-hardening
response. In some instances, the overall ductility of the alloy increases with the addition of TiB2 reinforcement. The flow stresses of both the monolithic and composite variants exhibit conventional power-law plasticity.
The results indicate that the strengthening and the flow behavior in these composites are derived from both indirect and direct
sources. Strengthening contributions are indirectly derived from the microstructural changes within the matrix of the composite
that evolve due to the presence of the reinforcement during its evolution and development, for example, due to grain refinement
and reinforcement-derived interstitial solid-solution strengthening. Direct contributions to strength are those that can be
specifically attributed to the presence of the reinforcement during deformation,e.g., through the interaction of dislocations with the reinforcing particles. When the estimates of the indirect contributions
are isolated and arithmetically removed from the magnitude of the total observed strength of the composite, the increase in
flow stress correlates in all instances with the inverse square root of the planar interparticle spacing for all alloy compositions,
heat treatments, and levels of strain examined. 相似文献
4.
S. K. Mannan K. S. Kumar J. D. Whittenberger 《Metallurgical and Materials Transactions A》1990,21(8):2179-2188
CoAl-base composites containing various volume fractions of TiB2 particulates in the 1 to 3-μm size range were tested in compression over a range of strain rates at 1100 to 1300 K. Hotpressed
and postcompression microstructures were characterized using optical and transmission electron microscopy. For a strain rate
of 2 × 10-6 s-1, the flow stress at 1300 K of CoAl-20 vol pct TiB2 was twice that of monolithic CoAl. Correspondingly, the stress exponent of CoAl-20 vol pct TiB2 at 1300 K was ∼4.5 compared to ∼3.0 for stoichiometric monolithic CoAl. This increased resistance of the composite to deformation
at elevated temperatures is attributed to TiB2 particulate-dislocation interactions. The high-temperature compressive deformation behaviors of NiAl-TiB2 and CoAl-TiB2 composites are compared. 相似文献
5.
C. A. Caracostas W. A. Chiou M. E. Fine H. S. Cheng 《Metallurgical and Materials Transactions A》1997,28(2):491-502
An investigation of the wear behavior, in lubricated sliding and rolling of in situ prepared TiB2 particle-reinforced 2024 T4 Al alloy matrix composites against 52100 steel and hardened pearlitic nodular cast iron, respectively,
was undertaken. In sliding contact, the 10 vol pct 0.3-μm TiB2-metal matrix composite (MMC) showed slightly less wear than the 10 vol pct 1.3-μm TiB2-MMC. Transmission electron microscopy of cross sections, taken normal to the wear track and parallel to the sliding direction,
revealed that the TiB2 particles on the wear track were polished and particle pullout was largely absent. This was attributed to the strong interfacial
bonding between the Al-alloy matrix and the TiB2 reinforcing phase. The TiB2 particles on the wear track inhibited spalling. Subsurface damage of the MMC did not occur. The wear of the steel mating
surfaces worn against the TiB2-MMCs was minor and caused by the cutting action of the TiB2 particles that resided on the MMC wear track. In rolling contact, the 0.3-μm-size TiB2-MMC showed 5 times higher weight loss than the 1.3-μm TiB2-MMC for the same content of reinforcement, but the weight loss of the cast iron mating surface was less for the former. For
the smaller particle size, the wear of 5 and 10 vol pct TiB2-MMCs was the same. A high density of surface cracks was present on the wear track of the 0.3-μm TiB2-MMC but not on the 1.3-μm MMC. The significance of strong particle/matrix interfacial bonding and particle size effect on the wear behavior of ceramic
particulate-reinforced MMCs in lubricated sliding and rolling wear is discussed. 相似文献
6.
S. R. Pritchett B. Mishra J. J. Moore 《Metallurgical and Materials Transactions B》1995,26(1):121-134
LiAl and LiGa intermetallic alloys have been synthesized using the simultaneous combustion mode of combustion synthesis. LiAl
intermetallic is potentially suitable as a temper alloy for producing aluminum-lithium alloys and as an anodic material for
high-energy batteries. LiGa can be used as a reduction alloy to recover valuable reactive metals from molten salt effluent
in actinide recovery technology. The effects of particle size, preignition heating rate, and theoretical green density on
the ignition and combustion temperatures have been studied in an effort to more precisely control the synthesis reaction of
these intermetallics. A lithium particle size of -20/xm was found to be suitable when the combustion synthesis reaction was conducted at a high heating rate (>1.0 cC/s) and a moderate
green density (55 to 65 pct theoretical). Preignition diffusion is suggested as the cause for low exothermic heat release
at high green densities. A combustion temperature above the melting point of the LiGa intermetallic compound can be achieved
under optimized conditions. However, the exothermicity and, therefore, the adiabatic temperature is too low for either LiAl
or LiGa to be produced by the propagating mode of combustion synthesis.
Formerly graduate student with the Kroll Institute for Extractive Metallurgy 相似文献
7.
G. He W. Löser L. Schultz J. Eckert 《Metallurgical and Materials Transactions A》2004,35(5):1591-1601
Copper mold cast cylinders of (Ti0.5Cu0.25Ni0.15Sn0.05Zr0.05)100−x
Mo
x
composites are prepared. Addition of Mo in the bulk glass-forming alloy induces the formation of a dendrite/matrix composite.
For 3-mm-diameter cylinders, the matrix exhibits a homogenous ultrafine microstructure for Mo content of 2.5 at. pct, and
a fine eutectic microstructure for 5 at. pct Mo. For 5-mm-diameter cylinders, the matrix exhibits a dendritic microstructure
for 2.5 at. pct Mo, and exhibits a coarser eutectic microstructure for 5 at. pct Mo. Despite the formation of a dendrite/nanostructured
matrix composite in the cylinders, the quenched surface layer with a nanoscale grain size dominates the deformation and fracture
of the 3-mm-diameter cylinders. More than 56 vol pct quenched layer leads to a distensile fracture mode and the samples exhibit
high fracture strength and high Young’s modulus but low ductility. For 5-mm-diameter cylinders, the composite microstructure
becomes dominant due to its more than 64 vol pct volume fraction leading to a cone-shaped fracture surface. The samples exhibit
lower yield strength and lower Young’s modulus but better ductility compared to the 3-mm-diameter cylinders. The mechanical
behavior of the Mo-bearing composites strongly depends on the microstructural homogeneity and casting defects formed upon
solidification. 相似文献
8.
Z. Y. Chen Y. Y. Chen G. Y. An Q. Shu D. Li Y. Y. Liu 《Metallurgical and Materials Transactions A》2000,31(8):1959-1964
A novel in situ reaction process-in-melt reaction method was developed. TiB2 particles form in situ through the reaction of TiO2, H3BO3, and Na3AlF6 in an aluminum alloy melt. The results showed that the in situ TiB2 particles formed were spherical in shape and had an average diameter of about 0.93 μm. Moreover, the distribution of TiB2 particles in the matrix was uniform. The interface between the TiB2 particles and the matrix showed good cohesion. The tensile strength and the yield strength of the composite increase with
increasing TiB2 content. When TiB2 particle content in the matrix was 10 vol pct, the tensile strength, yield strength, and elongation of Al-4.5Cu/TiB2 composite were 417 MPa, 317 MPa, and 3.3 pct, respectively. 相似文献
9.
Ti57−x
Cu15Ni14Sn4+x
Nb10 (x = 0, 5, or 10) alloys were prepared by copper mold casting. At Sn = 4 at. pct, a dendrite/ultrafine-structured multicomponent
alloy was obtained, which exhibits 1271 MPa yield strength, 77 GPa Young’s modulus, and 2 pct plasticity at room temperature
for 3-mm-diameter samples. The cooling rate significantly affects the as-cast microstructure and the mechanical properties.
For 5-mm-diameter samples, the alloy exhibits 1226 MPa yield strength, 63 GPa Young’s modulus, and 2.5 pct plasticity. At
Sn = 9 at. pct, Ti-, Sn-, and Nb-rich particles precipitate primarily. This near-hypereutectic alloy composition leads to
the precipitation of intermetallics, which deteriorate the mechanical properties and result in the coexistence of ductile
and brittle fracture mechanisms. At Sn = 14 at. pct, the alloy composition is completely in the intermetallic region, thus
inducing the formation of Ti2Cu, Ti2Ni, and Ti3Sn intermetallics. The alloy becomes very brittle because the intermetallic compounds dominate the fracture process. 相似文献
10.
Hajime Iwasaki Takasuke Mori Mamoru Mabuchi Kenji Higashi 《Metallurgical and Materials Transactions A》1998,29(2):677-683
High-strain-rate superplastic behavior has been investigated for Si3N4p
/Al-Mg-Si (6061) composites with a V
f
=20 and 30 pct, respectively, where V
f
is the volume fraction of reinforcements. A maximum elongation was attained at a temperature close to the onset temperature
for melting for both composites. The maximum elongation for the 30 vol pct composite was larger than that for the 20 vol pct
composite. Development of cavities transverse to the tensile direction is responsible for the lower maximum elongation of
the 20 vol pct composite. However, development of the transverse cavities was limited to the optimum superplastic temperature
for the 30 vol pct composite. The differential scanning calorimetry (DSC) investigation showed that a sharp endothermic peak
appeared for the 30 vol pct composite, indicating that sufficient partial melting occurs. It is, therefore, likely that the
stress concentrations are sufficiently relaxed by a liquid phase and that the development of transverse cavities is limited
for the 30 vol pct composite. 相似文献
11.
N. C. Beck Tan R. M. Aikin R. M. Briber 《Metallurgical and Materials Transactions A》1994,25(11):2461-2467
The effect of particle size, particle volume fraction, and matrix microstructure on the fracture initiation toughness of a
discontinuously reinforced aluminum composite was examined. The composites were Al-4 wt pct Cu-1.5 wt pct Mg reinforced with
0 to 15 vol pct of TiB2 having an average particle diameter of 1.3 or 0.3μm producedin situ by the XD process. The room-temperature plane-strain toughness measured using compact tension specimens ranged from 19 to
25 MPa
. Toughness was adversely affected by increases in TiB2 volume fraction. The fracture toughness of all composites was affected by changes in the matrix microstructure produced by
aging. The response of the composites to artificial aging deviates from that of the matrix. Fractography revealed that these
composites failed in a ductile manner, with voids initiating at the reinforcing TiB2 particles. The experimentally measured plane-strain toughness properties of Al-4Cu-l .5Mg composites with well-dispersed,
1.3-μm TiB2 reinforcements agree with the Rice and Johnson model. 相似文献
12.
Y. Hotta Y. Kaneno T. Takasugi T. Tetsui 《Metallurgical and Materials Transactions A》2006,37(2):361-369
Thermomechanically processed TiAl-based intermetallic alloys with various alloy compositions and microstructures were tensile
tested in various environmental media, including air, water vapor, and a gas mixture of 5 vol pct, H2 + Ar, as functions of temperature and strain rate. All the TiAl-based intermetallic alloys showed reduced tensile fracture
stress (or elongation) in air, in water vapor, and in a gas mixture of 5 vol pct H2 + Ar, not only at ambient temperature (RT ∼ 600 K), but also at high temperature, from 600 to 1000 K (and sometimes at temperatures higher than 1000 K). The high-temperature
environmental embrittlement of TiAl-based intermetallic alloys depended upon the microstructure. The factors causing the high-temperature
environmental embrittlement may include hydrogen atoms decomposed from water vapor (H2O) or hydrogen gas (H2), similar to those causing the low-temperature environmental embrittlement. Also, it is demonstrated that the oxidized scale
is effective in reducing high-temperature environmental embrittlement. 相似文献
13.
Effects of TiB2/TiCx ratios on compression properties and abrasive wear resistance of 50?vol.-% (TiB2–TiCx)/Al–Cu composites fabricated via the combustion synthesis (CS) method assisted with hot press from the Al–Ti–B4C system were studied. With decrease in the TiB2/TiCx ratio from 3:1 to 1:3, the shape of TiB2 changed from platelike to clubbed while the size of TiCx particles increased, which directly led to different mechanical properties. The 50?vol.-% (TiB2–TiCx)/Al–Cu composite with the TiB2/TiCx ratio of 2:1 exhibited good compression strength without sacrificing the fracture strain, while the composite possessed the highest abrasive wear resistance when the TiB2/TiCx ratio was 3:1. The appropriate TiB2/TiCx ratio was recommended to be 2:1 in this research. 相似文献
14.
Minoru Furukawa Jingtao Wang Zenji Horita Minoru Nemoto Yan Ma Terence G. Langdon 《Metallurgical and Materials Transactions A》1995,26(3):633-639
Experiments were conducted to compare the influence of temperature on the flow and strain-hardening characteristics of an
Al-6061 metal matrix composite, reinforced with ∼20 vol pct of Al2O3-based microspheres, with the unreinforced monolithic alloy. At room temperature, the yield stresses and the strain-hardening
rates are higher in the composite material in the asquenched condition and after aging at 448 K for periods of time up to
300 hours. The 0.2 pct proof stress and the strain-hardening rate decrease with increasing temperature in both materials,
but the rate of decrease is faster in the composite so that the unreinforced monolithic alloy exhibits higher yield stresses
and strain-hardening rates at temperatures in the vicinity of 600 K. Under conditions of constant stress at high temperatures,
the composite exhibits both a higher creep strength than the monolithic alloy and higher values for the stress exponents for
creep.
Formerly Visiting Scholar, Kyushu University, is Associate Professor, Department of Metallurgy, Xian Institute of Metallurgy
and Construction Engineering, Xian 710055, People’s Republic of China. 相似文献
15.
16.
H. C. Yi J. Y. Guigné T. C. Woodger J. J. Moore 《Metallurgical and Materials Transactions B》1998,29(4):889-897
The effects of gravity on the combustion characteristics and microstructure of metal-ceramic composites (HfB2/Al and Ni3Ti/TiB2 systems) were studied under both normal and low gravity conditions. Under normal gravity conditions, pellets were ignited
in three orientations relative to the gravity vector. Low gravity combustion synthesis (SHS) was carried out on a DC-9 aircraft
at the NASA-Lewis Research Center. It was found that under normal gravity conditions, both the combustion temperature and
wave velocity were highest when the pellet was ignited from the bottom orientation; i.e., the wave propagation direction was directly opposed to the gravitational force. The SHS of 70 vol pct Al (in the Al-HfB2 system) was changed from unstable, slow, and incomplete when ignited from the top to unstable, faster, and complete combustion
when ignited from the bottom. The hydrostatic force (height × density × gravity) in the liquid aluminum was thought to be
the cause of formation of aluminum nodules at the surface of the pellet. The aluminum nodules that were observed on the surface
of the pellet when reacted under normal gravity were totally absent for reactions conducted under low gravity. Buoyancy of
the TiB2 particles and sedimentation of the Ni3Ti phase were observed for the Ni3Ti/TiB2 system. The possibility of liquid convective flow at the combustion front was also discussed. Under low gravity conditions,
both the combustion temperature and wave velocity were lower than those under normal gravity. The distribution of the ceramic
phase, i.e., TiB2 or HfB2, in the intermetallic (Ni3Ti) or reactive (Al) matrix was more uniform. 相似文献
17.
Kusunoki K. Sumino K. Kawasaki Y. Yamazaki M. 《Metallurgical and Materials Transactions A》1990,21(2):547-555
The effects of the amount of γ′ and yttria (Y2O3) content on the secondary recrystallization (SRx) temperature of as-extruded material of the mechanically alloyed nickel-base
superalloys based on a superalloy TMO-2 were investigated. It was observed that (1) the primarily recrystallized grain size
of the as-extruded material decreased with increasing the γ′ and the yttria content in the material; (2) the SRx temperature
decreased with decreasing the yttria content and with increasing the amount of theγ′ up to about 55 vol pct, while (3) the temperature increased for the material containing more than 65 vol pctγ′; and (4) the SRx temperatures of the material containing 75 vol pctγ′ phase with 1.1 wt pct yttria and 55 vol pctγ′ phase with no yttria were identical to theirγ′ solvus. From these results, the following conclusions are drawn: (1) dissolution of theγ′ particles is a necessary, but not a sufficient, condition for the occurrence of secondary recrystallization; (2) secondary
recrystallization of a material with sufficiently smaller grain size occurs at a temperature higher than theγ′ solvus and the temperature at which the yttria particles lose their ability to prevent rapid growth of the primarily recrystallized
grains; and (3) the SRx temperature of a material with larger grain size depends on grain size.
Formerly Assistant Researcher with NRIM 相似文献
18.
E. Frás A. Janas S. Wierzbiński H. F. Lopez 《Metallurgical and Materials Transactions A》2002,33(12):3831-3838
The deformation behavior of TiC particulate-reinforced aluminum composites (Al-TiC
p
) was investigated in this work using pure aluminum as the reference matrix material. Uniaxial compression tests were carried
out at 293 and 623 K and at two strain rates (3.7×10−4 and 3.7×10−3 s−1). Yield strengths of up to 127 MPa were found in composites containing 10 vol pct TiC particulates, which were almost 4 times
the yield strength of pure Al. In addition, at 623 K, relatively small reductions in yield strength were found, suggesting
that this property was rather insensitive to temperature for the temperatures investigated in this work. Nevertheless, at
623 K, increasing the rate of straining from 3.7×10−4 s−1 to 3.7×10−3 s−1 lowered the yield strength, particularly in 10 vol pct TiC
p
-Al composites. Two stages of work hardening were identified in pure Al and a 10 vol pct TiC
p
composite during plastic flow through the modified version of the Hollomon equation (σ = Kɛ
n ± Δ). In particular, the work-hardening exponents found in pure Al shifted from high to low values as the extent of plastic
strain was increased while the opposite was true for the 10 vol pct TiC
p
composite. Finally, at 623 K, dynamic recovery mechanisms became dominant at plastic strain levels >0.2 in 10 vol pct TiC
p
-Al composites, with the effect being minor at room temperature. 相似文献
19.
Megan Frary Christopher Schuh David C. Dunand 《Metallurgical and Materials Transactions A》2002,33(6):1669-1680
By thermally cycling through their transformation temperature range, coarse-grained polymorphic materials can be deformed
superplastically, owing to the emergence of transformation mismatch plasticity (or transformation superplasticity) as a deformation
mechanism. This mechanism is presently investigated under biaxial stress conditions during thermal cycling of unalloyed titanium,
Ti-6Al-4V, and their composites (Ti/10 vol. pct TiC
p
, Ti-6Al-4V/10 vol. pct TiC
p
, and Ti-6Al-4V/5 vol. pct TiB
w
). During gas-pressure dome bulging experiments, the dome height was measured as a function of forming time. Adapting existing
models of biaxial doming to the case of transformation superplasticity where the strain-rate sensitivity is unity, we verify
the operation of this deformation mechanism in all experimental materials and compare the biaxial results directly to new
uniaxial thermal cycling results on the same materials. Finally, existing thickness distribution models are compared with
experimentally measured profiles. 相似文献
20.
Reaction synthesis of Ni-Al-based particle composite coatings 总被引:1,自引:0,他引:1
D. F. Susan W. Z. Misiolek A. R. Marder 《Metallurgical and Materials Transactions A》2001,32(2):379-390
Electrodeposited metal matrix/metal particle composite (EMMC) coatings were produced with a nickel matrix and aluminum particles.
By optimizing the process parameters, coatings were deposited with 20 vol pct aluminum particles. Coating morphology and composition
were characterized using light optical microscopy (LOM), scanning electron microscopy (SEM), and electron probe microanalysis
(EPMA). Differential thermal analysis (DTA) was employed to study reactive phase formation. The effect of heat treatment on
coating phase formation was studied in the temperature range 415 °C to 1000 °C. Long-time exposure at low temperature results
in the formation of several intermetallic phases at the Ni matrix/Al particle interfaces and concentrically around the original
Al particles. Upon heating to the 500 °C to 600 °C range, the aluminum particles react with the nickel matrix to form NiAl
islands within the Ni matrix. When exposed to higher temperatures (600 °C to 1000 °C), diffusional reaction between NiAl and
nickel produces (γ′)Ni3Al. The final equilibrium microstructure consists of blocks of (γ′)Ni3Al in a γ(Ni) solid solution matrix, with small pores also present. Pore formation is explained based on local density changes during
intermetallic phase formation, and microstructural development is discussed with reference to reaction synthesis of bulk nickel
aluminides. 相似文献