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1.
Chang-Young Son Gyeong Su Kim Sang-Bok Lee Sang-Kwan Lee Hyoung Seop Kim Sunghak Lee 《Metallurgical and Materials Transactions A》2012,43(6):1911-1920
In this study, amorphous matrix composites, whose matrix was a Zr-based amorphous alloy and reinforcements were tungsten continuous
fibers or porous foams, were fabricated by the liquid pressing process, and their dynamic compressive properties were investigated.
Approximately 65 to 69 vol pct of tungsten fibers or foams were distributed homogeneously in the amorphous matrix, whereas
defects such as misinfiltration or pores were eliminated. According to the dynamic compressive test results of the tungsten-fiber-reinforced
composite, tungsten fibers worked to withstand a considerable amount of applied loads, whereas the amorphous matrix sustains
bent or bucked fibers, thereby leading to the maximum strength of 3328 MPa and the plastic strain of 2.6 pct. In the tungsten-foam-reinforced
composite, the compressive stress continued to increase according to the work hardening after the yielding, thereby leading
to the maximum strength of 3458 MPa and the plastic strain of 20.6 pct. This dramatic increase in maximum strength and plastic
strain was attributed to the simultaneous and homogeneous deformation at tungsten foams and amorphous matrix because tungsten
foams did not show anisotropy and tungsten/matrix interfaces were excellent. These findings suggested that tungsten-foam-reinforced
composite could be applied to penetrators, in which the self-sharpening should be well promoted while keeping high specific
gravity, sufficient strength, and plastic strain because cracks were formed at some heavily deformed tungsten foams by the
shear fracture. 相似文献
2.
3.
Sang-Bok Lee Kyuhong Lee Sang-Kwan Lee Sunghak Lee 《Metallurgical and Materials Transactions A》2009,40(13):3159-3170
An STS304-continuous-fiber-reinforced Zr-based amorphous alloy matrix composite with excellent fiber/matrix interfaces was
fabricated without pores and misinfiltration by liquid pressing process. Approximately 60 vol pct of continuous fibers were
homogeneously distributed in the matrix, in which considerable amounts of polygonal and dendritic crystalline phases were
formed by the diffusion of metallic elements from the fibers. The ductility of the composite under compressive or tensile
loading was drastically improved over that of the monolithic amorphous alloy. According to the compressive test results, a
strength of 700 to 830 MPa was sustained until reaching a strain of 40 pct, because fibers interrupted the propagation of
shear bands initiated in the matrix and took over a considerable amount of load. Under tensile loading, the deformation and
fracture occurred by crack formation and opening at matrices, necking of fibers, fiber/matrix interfacial separation, and
cup-and-cone–type fracture of fibers, thereby resulting in a high tensile elongation of 27 pct. 相似文献
4.
5.
Amit S. Sharma Krishanu Biswas Bikramjit Basu Dibyendu Chakravarty 《Metallurgical and Materials Transactions A》2011,42(7):2072-2084
For the first time, we report here that high purity nanocrystalline Cu and Cu-10 wt pct Pb alloys can be densified with more
than 90 pct theoretical density at a low temperature of 623 K (350 °C) using spark plasma sintering (SPS) in argon atmosphere
at a pressure of 100 MPa. Scanning electron microscopy (SEM) analysis indicates that molten Pb particles travel through Cu
grain boundaries, delineating a “flowlike” pattern in the microstructure. An extensive transmission electron microscopy (TEM)
analysis of the ultrafine scale microstructure reveals partial wetting of Cu by liquid Pb as well as entrapment of Pb particles
within the Cu matrix. The sintering kinetics and microstructural evolution are discussed in reference to the intrinsic characteristics
of SPS as well as phase equilibria in the Cu-Pb system. An important result is that high hardness of around 2 GPa is measured
in the Cu-10 wt pct Pb nanostructured alloy, SPS at 573 K to 623 K (300 °C to 350 °C). 相似文献
6.
7.
Haouaoui M. Karaman I. Harwig K. T. Maier H. J. 《Metallurgical and Materials Transactions A》2004,35(9):2935-2949
The consolidation of copper micro- and nanoparticles (325 mesh, 130 nm, and 100 nm) was performed using room-temperature equal-channel
angular extrusion (ECAE). The effects of extrusion route, number of passes, and extrusion rate on consolidation performance
were evaluated. The evolution of the microstructure and the mechanical behavior of the consolidates were investigated and
related to the processing route. Possible deformation mechanisms are proposed and compared to those in ECAE-processed bulk
Cu. A combined high ultimate tensile stress (470 MPa) and ductility (∼20 pct tensile fracture strain) with near-elasto-plastic
behavior was observed in consolidated 325-mesh Cu powder. On the other hand, early plastic instability took place, leading
to a continuous softening in flow stress of bulk ECAE-processed copper. Increases in both strength and ductility were evident
with an increasing number of passes in the bulk samples, which appears to be inconsistent with grain-boundary-moderated deformation
mechanisms for a microstructure with an average grain size of 300 to 500 nm. Instead, this increase is attributed to microstructural
refinement and to dynamic recovery and bimodal grain-size distribution. Near-perfect elastoplasticity in consolidated 325-mesh
Cu powder is explained by a combined effect of strain hardening accommodated by large grains in the bimodal structure and
softening caused by recovery mechanisms. Compressive strengths as high as 760 MPa were achieved in consolidated 130-nm copper
powder. Although premature failure occurred during tensile loading in 130-nm consolidated powder, the fracture strength was
still about 730 MPa. The present study shows that ECAE consolidation of nanoparticles opens a new possibility for the study
of mechanical behavior of bulk nanocrystalline (NC) materials, as well as offering a new class of bulk materials for practical
engineering applications. 相似文献
8.
Kaveh Edalati Zenji Horita Hiroshi Fujiwara Kei Ameyama 《Metallurgical and Materials Transactions A》2010,41(13):3308-3317
Pure Ti (99.5 pct) powders after processing with ball milling (BM) were consolidated to disc-shaped samples with 10-mm diameter
and 0.8-mm thickness at room temperature using high-pressure torsion (HPT). A relative density as high as 99.9 pct, high bending
and tensile strengths of 2.55 to 3.45 and 1.35 GPa, respectively, and a moderate ductility of 8 pct with an ultrafine grained
structure are achieved after cold consolidation with HPT, which exceed those of hot consolidation methods. X-ray diffraction
(XRD) analysis showed that a phase transformation occurs from α phase to ω phase during HPT under a pressure of 6 GPa as in bulk pure Ti, whereas no phase transformation is detected after processing
with BM alone. It was confirmed that the strength and ductility are improved by a combined application of BM and HPT when
compared with other severe plastic deformation methods applied to Ti and Ti-6 pct Al-4 pct V, so that no alloying elements
are required for the achievement of a comparable strength and ductility. 相似文献
9.
Marie E. Cox Suveen N. Mathaudhu K. Ted Hartwig David C. Dunand 《Metallurgical and Materials Transactions A》2010,41(7):1706-1713
Interpenetrating phase composites are created by warm equal channel angular extrusion (ECAE) of blended powders of amorphous
Zr58.5Nb2.8Cu15.6Ni12.8Al10.3 (Vit106a) and a crystalline ductile metal (Cu, Ni, or W). Subsequent dissolution of the continuous metallic phase results
in amorphous Vit106a foams with ~40 pct aligned, elongated pores. The extent of Vit106a powder densification in the composites
improves with the strength of the crystalline metallic powder, from low for Cu to high for W, with a concomitant improvement
in foam compressive strength, ductility, and energy absorption. 相似文献
10.
J. A. Jiménez G. González-Doncel O. A. Ruano 《Metallurgical and Materials Transactions A》1996,27(7):1861-1867
The present work is part of an investigation into the use of rapid solidification and powder metallurgy techniques to obtain
iron-boron alloys with good mechanical properties. Two Fe-B binary alloys and two ultrahigh boron tool steels were gas atomized
and consolidated by hot isostatic pressing (HIP) at temperatures ranging from 700 °C to 1100 °C to have a fine microstructure.
Optimum properties were achieved for the binary alloys at low consolidation temperatures, since the solidification mi-crostructure
from the original powders is eliminated and, at the same time, fine microstructures and low porosity are obtained in the alloys.
At high temperatures and low strain rates, three of the four alloys exhibited low stress exponents, but only the Fe-2.2 pct
B alloy showed tensile elongations higher than 100 pct. At low temperatures, only the Fe-2.2 pct B alloy deformed plastically.
This alloy showed values of tensile elongation and ultimate tensile strength that were strongly dependent on testing and consolidation
temperatures.
J.A. JIMéNEZ, Postdoctoral Fellow, formerly with Centra Nacional de Investigaciones Metalúrgicas, C.S.I.C 相似文献
11.
Chang-Young Son Gyeong Su Kim Sang-Bok Lee Sang-Kwan Lee Hyoung Seop Kim Hoon Huh Sunghak Lee 《Metallurgical and Materials Transactions A》2012,43(11):4088-4096
A Zr-based amorphous matrix composite reinforced with tungsten continuous fibers in an amorphous LM2 alloy matrix containing ductile ?? dendrites was fabricated without pores or defects by the liquid pressing process, and its tensile and compressive properties were examined in relation with microstructures and deformation mechanisms. Overall, 68?vol pct of tungsten fibers were distributed in the matrix, in which 35?vol pct of ?? dendrites were present. The LM2 composite had the greatly improved tensile strength and elastic modulus over the LM2 alloy, and it showed a stable crack propagation behavior as cracks stopped propagating at the longitudinal cracks of tungsten fibers or ductile ?? dendrites. According to the compressive test results, fracture did not take place at one time after the yield point, but it proceeded as the applied loads were sustained by fibers, thereby leading to the maximum strength of 2432?MPa and plastic strain of 16.4?pct. The LM2 composite had the higher strength, elastic modulus, and ductility under both tensile and compressive loading conditions than the tungsten-fiber-reinforced composite whose matrix did not contain ?? dendrites. These distinctively excellent properties indicated a synergy effect arising from the mixing of amorphous matrix and tungsten fibers, as well as from the excellent bonding of interfaces between them. 相似文献
12.
Zhihui Zhang Bing Q. Han Kyung H. Chung Enrique J. Lavernia 《Metallurgical and Materials Transactions A》2006,37(7):2265-2273
The current study aims to provide fundamental insight into the behavior of microstructures containing grain sizes that span
multiple length scales. A commercial 5083 Al alloy was selected as the material of interest to facilitate comparison with
recently published data. The materials studied here were prepared via the thermal consolidation of powders that were cryomilled
for different times (i.e., 0, 2, 4, and 8 hours). Following consolidation, the resultant microstructure was characterized by an equiaxed grain morphology
with a size distribution centered around 200∼300 nm. Dispersed among the 200- to 300-nm grains were coarse-grained regions
or ligaments with a grain size ranging from 600 nm to 2 μm. The occurrence of coarse-grained regions is rationalized on the
basis of recrystallization or subgrain coarsening, whereas the occurrence of equiaxed fine regions is proposed to be a result
of continuous grain growth. Two types of microstructures were selected for study, containing coarse-grained volumes of approximately
28 pct and 43 pct that corresponded to an ultimate tensile strength (UTS) of 566 MPa and 535 MPa, and a fracture strain of
3.2 pct and 3.5 pct, respectively. The observed ductility and the relevant toughening mechanisms were discussed in light of
the presence of multiple length scales. 相似文献
13.
G. Dirras T. Chauveau A. Abdul-Latif J. Gubicza S. Ramtani Q. Bui Z. Hegedűs B. Bacroix 《Metallurgical and Materials Transactions A》2012,43(4):1312-1322
Commercial-purity (99 wt pct), bulk, ultrafine-grained aluminum samples were produced by a two-step process that combines
powder consolidation by hot isostatic pressing and dynamic plastic deformation. The compaction step yielded crystallographic
texture-free specimens with an average grain size of approximately 2 μm. Then, some of the consolidated specimens were deformed dynamically at room temperature at an initial strain rate of 370 seconds−1 and up to an axial strain of ε = 1.25. After dynamic plastic deformation, the grain size and the dislocation density were approximately 500 nm and 1014 m−2, respectively. The yield strength was approximately 77 MPa for the as-consolidated sample, which increased up to approximately
103 MPa and 120 MPa for the impacted samples along the axial and radial directions, respectively. The compression stress as
a function of strain showed saturation behavior for the axially deformed samples, whereas the specimens deformed along the
radial direction exhibited significant strain softening. The latter behavior is explained mainly by the weakening of the crystallographic
texture that occurred because of the strain-path change along the radial direction. 相似文献
14.
Gyeong Su Kim Sang-Bok Lee Sang-Kwan Lee Hyoung Seop Kim Sunghak Lee 《Metallurgical and Materials Transactions A》2014,45(3):1284-1293
In this study, two Zr-based amorphous alloy matrix composites reinforced with STS304 stainless steel continuous fibers whose diameters were 110 and 250 μm were fabricated by the liquid pressing process. Using a Hopkinson pressure bar, the compressive deformation behavior was investigated at a strain rate of about 103 s?1, and the results were then compared with those obtained under quasi-static loading. 65 to 68 vol pct of STS fibers were homogeneously distributed in the amorphous matrix, in which considerable amounts of dendritic crystalline phases were present. According to the dynamic compressive test results, shear cracks were formed at the maximum shear stress direction in the 110-μm-diameter-fiber-reinforced composite to reach the final failure. In the 250-μm-diameter-fiber-reinforced composite, fibers were not cut by shear cracks because the fiber diameter was large enough to restrict the propagation of shear cracks, while taking over a considerable amount of compressive loads over 1500 MPa. This composite showed the higher yield and maximum compressive strengths and plastic strain than the 110-μm-diameter-fiber-reinforced composite because of the sufficient ductility of STS fibers, the effective interruption of propagation of shear cracks, and the strain hardening of fibers themselves. 相似文献
15.
Pavel Salvetr Tomáš František Kubatík Damien Pignol Pavel Novák 《Metallurgical and Materials Transactions B》2017,48(2):772-778
This work is focused on the possibilities of preparing Ni-Ti46 wt pct alloy by powder metallurgy methods. The self-propagating high-temperature synthesis (SHS) and combination of SHS reaction, milling, and spark plasma sintering consolidation (SPS) are explored. The aim of this work is the development of preparation method with the lowest amount of undesirable phases (mainly Ti2Ni phase). The SHS with high heating rate (approx. 200 and 300 K min?1) was applied. Because the SHS product is very porous, it was milled in vibratory disk milling and consolidated by SPS technique at temperatures of 1173 K, 1273 K, and 1373 K (900 °C, 1000 °C, and 1100 °C). The microstructures of samples prepared by SHS reaction and combination of SHS reaction, milling, and SPS consolidation are compared. The changes in microstructure with increasing temperature of SPS consolidation are observed. Mechanical properties are tested by hardness measurement. The way to reduce the amount of Ti2Ni phase in structure is leaching of powder in 35 pct hydrochloric acid before SPS consolidation. 相似文献
16.
A. Belyakov Y. Sakai T. Hara Y. Kimura K. Tsuzaki 《Metallurgical and Materials Transactions A》2002,33(10):3241-3248
The structural changes in an Fe-0.6 pct O alloy during mechanical milling followed by consolidation through rolling were studied.
The iron-iron oxide powders were mechanically milled in an argon atmosphere for various times from 20 to 300 hours. The powders
were then canned into a steel pipe and multiple rolled at 700 °C for consolidation. The microstructure of the final product
depended significantly on the milling time. The volume fraction of the dispersed oxides (10 nm in diameter) increased from
about 0.3 to 2.5 pct when the milling time was increased from 20 to 300 hours. The relatively short milling time of 20 hours
resulted in the evolution of elongated grains (an average size of about 1.2 μm) with a large fraction of low-angle grain boundaries after consolidation. In contrast, much finer grains (about 0.2 μm in size) with a near random grain-boundary misorientation distribution evolved in the samples milled for 300 hours. 相似文献
17.
D. Roy R. Mitra O. A. Ojo W. Lojkowski I. Manna 《Metallurgical and Materials Transactions A》2011,42(8):2498-2508
The structure and mechanical properties of nanocrystalline intermetallic phase dispersed amorphous matrix composite prepared
by hot isostatic pressing (HIP) of mechanically alloyed Al65Cu20Ti15 amorphous powder in the temperature range 573 K to 873 K (300 °C to 600 °C) with 1.2 GPa pressure were studied. Phase identification
by X-ray diffraction (XRD) and microstructural investigation by transmission electron microscopy confirmed that sintering
in this temperature range led to partial crystallization of the amorphous powder. The microstructures of the consolidated
composites were found to have nanocrystalline intermetallic precipitates of Al5CuTi2, Al3Ti, AlCu, Al2Cu, and Al4Cu9 dispersed in amorphous matrix. An optimum combination of density (3.73 Mg/m3), hardness (8.96 GPa), compressive strength (1650 MPa), shear strength (850 MPa), and Young’s modulus (182 GPa) were obtained
in the composite hot isostatically pressed (“hipped”) at 773 K (500 °C). Furthermore, these results were compared with those
from earlier studies based on conventional sintering (CCS), high pressure sintering (HPS), and pulse plasma sintering (PPS).
HIP appears to be the most preferred process for achieving an optimum combination of density and mechanical properties in
amorphous-nanocrystalline intermetallic composites at temperatures ≤773 K (500 °C), while HPS is most suited for bulk amorphous
alloys. Both density and volume fraction of intermetallic dispersoids were found to influence the mechanical properties of
the composites. 相似文献
18.
Osman Ertorer Troy D. Topping Ying Li Wes Moss Enrique J. Lavernia 《Metallurgical and Materials Transactions A》2011,42(4):964-973
Cryomilled nanocrystalline commercially pure (CP)-Ti powders were spark plasma sintered (SPS) using different process parameters
(heating rate, temperature, pressure, and dwell time) to study densification, microstructure, and mechanical behavior. The
results were rationalized on the basis of the relevant literature and experimental results, and they reveal a strong dependence
on SPS parameters. An interesting finding was that the measured high ductility was accompanied by a moderate strength (yield
strength [YS] = 770 MPa, ultimate tensile strength [UTS] = 840 MPa with ~27 pct elongation to failure). The combinations of
microstructure and mechanical response were attributed to the multistep processing at different temperature ranges as well
as to the presence of interstitial solutes. 相似文献
19.
Oscar A. Ruano Lawrence E. Eiselstein Oleg D. Sherby 《Metallurgical and Materials Transactions A》1982,13(10):1785-1792
Superplastic properties of three different composition white cast irons were investigated in the temperature range of 630
to 725 °C. Fine structures consisting of 1 to 2 μm ferrite grains were developed in these materials by consolidation of rapidly
solidified powders at intermediate temperatures below the A1 critical temperature. Tensile elongations of 1410 pct were found for a 3.0 pct C + 1.5 pct Cr white cast iron, 940 pct for
a 3.0 pct C white cast iron, and 480 pct for a 2.4 pct C white cast iron when tested at 700 °C and at a strain rate of 1 pct
per minute. The superplastic white cast irons exhibited a high strain rate sensitivity exponent,m, of 0.5 and activation energies for plastic flow were found to be nearly equal to the activation energy for grain boundary
self-diffusion in iron. These observations are in agreement with the creep behavior of superplastic materials controlled by
grain boundary diffusion.
OSCAR A. RUANO, formerly with the Department of Materials Science and Engineering, Stanford University.
LAWRENCE E. EISELSTEIN, formerly with the Department of Materials Science and Engineering, Stanford University. 相似文献
20.
C.M. Ho C.C. Leung Y.L. Yip S.W. Mok H.W. Kui 《Metallurgical and Materials Transactions A》2010,41(13):3443-3451
Fe83C17 alloy melt can be cast readily into white cast iron. It is brittle, with a compressive strength of ~1300 MPa. By a fluxing
technique, a Fe83C17 melt can be quenched into a crystalline solid of ultrafine networklike microstructure, with a hardness value of ~536 HV,
a yield strength of ~2000 MPa, and a strain to failure of about 18 pct. In particular, a cube made of Fe83C17 network alloy can be compressed to a disk. 相似文献