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1.
Patrick B. Berbon Terence G. Langdon Nikolai K. Tsenev Ruslan Z. Valiev Minoru Furukawa Zenji Horita Minoru Nemoto 《Metallurgical and Materials Transactions A》1998,29(9):2237-2243
Ultrafine grain sizes were introduced into samples of an Al-3 pct Mg solid solution alloy and a cast Al-Mg-Li-Zr alloy using
the process of equal-channel angular (ECA) pressing. The Al-3 pct Mg alloy exhibited a grain size of ∼0.23 μm after pressing
at room temperature to a strain of ∼4, but there was significant grain growth when the pressed material was heated to temperatures
above ∼450 K. The Al-Mg-Li-Zr alloy exhibited a grain size of ∼1.2 μm, and the microstructure was heterogeneous after pressing
to a strain of ∼4 at 673 K and homogeneous after pressing to a strain of ∼8 at 673 K with an additional strain of ∼4 at 473
K. The heterogeneous material exhibited superplastic-like flow, but the homogeneous material exhibited high-strain-rate superplasticity
with an elongation of >1000 pct at 623 K at a strain rate of 10−2 s−1. It is concluded that a homogeneous microstructure is required, and therefore a high pressing strain, in order to attain
high-strain-rate superplasticity (HSR SP) in ultrafine-grained materials.
This article is based on a presentation made in the symposium “Mechanical Behavior of Bulk Nanocrystalline Solids,” presented
at the 1997 Fall TMS Meeting and Materials Week, September 14–18, 1997, in Indianapolis, Indiana, under the auspices of the
Mechanical Metallurgy (SMD), Powder Materials (MDMD), and Chemistry and Physics of Materials (EMPMD/SMD) Committees. 相似文献
2.
Kiyoshi Matsubara Yuichi Miyahara Zenji Horita Terence G. Langdon 《Metallurgical and Materials Transactions A》2004,35(6):1735-1744
Experiments were conducted to evaluate the utility of a new processing procedure developed for Mg-based alloys in which samples
are subjected to a two-step processing route of extrusion followed by equal-channel angular pressing (designated as EX-ECAP).
The experiments were conducted using a Mg-0.6 wt pct Zr alloy and, for comparison purposes, samples of pure Mg. It is shown
that the potential for successfully using ECAP increases in both materials when adopting the EX-ECAP procedure. For the Mg-Zr
alloy, the use of EX-ECAP produces a grain size of ∼1.4 μm when the pressing is undertaken at 573 K. By contrast, using EX-ECAP with pure Mg at 573 K produces a grain size of ∼26
μm. Tensile testing of the Mg-Zr alloy at 523 and 573 K after processing by EX-ECAP revealed the occurrence of significantly
enhanced ductilities with maximum elongations of ∼300 to 400 pct. 相似文献
3.
Room temperature tension-tension fatigue tests were performed on two lamellar γ/γ′-δ alloys, one with 0 pct Cr and one with
6 pct Cr. The 6 pct Cr alloy was solidified at 3 cmJh while the 0 pct Cr alloy was solidified at 3 cm/h and 5.7 cm/h. Fatigue
testing was done on both alloys in the as-directionally solidified condition and on the 0 pct Cr alloy after heat treatment.
Increasing the growth speed of the 0 pct Cr alloy increased the fatigue life of the material at stresses above the 107 cycle fatigue limit. Partial solution treating and aging of the 0 pct Cr alloy,R = 3 cm/h, increased the fatigue life relative to the as-directionally solidified material at high stresses, to the same extent
as increasing the growth speed. Full solution treatment and aging of the 0 pct Cr alloy,R = 5.7 cm/ h, caused a reduction in the fatigue life relative to the as-directionally solidified material. Fatigue cracking
tended to be faceted in the 6 pct Cr alloy as opposed to the more ductile failure of the 0 pct Cr alloy. Microstructural perfection,
grain size and shape, interlamellar spacing, longitudinal cracking, and longitudinal and transverse ductility all are believed
to have influenced the fatigue resistance of the alloys. 相似文献
4.
Influence of pressing speed on microstructural development in equal-channel angular pressing 总被引:8,自引:0,他引:8
Patrick B. Berbon Minoru Furukawa Zenji Horita Minoru Nemoto Terence G. Langdon 《Metallurgical and Materials Transactions A》1999,30(8):1989-1997
The influence of pressing speed in equal-channel angular (ECA) pressing was investigated using samples of pure Al and an Al-1
pct Mg alloy and a range of pressing speeds from ∼10−2 to ∼10 mm s−1. The results show that the speed of pressing has no significant influence on the equilibrium grain size, at least over the
range used in these experiments. Thus, the equilibrium grain sizes were ∼1.2 μm for pure Al and ∼0.5 μm for the Al-1 pct Mg alloy for all pressing conditions. However, it is shown that the nature of the microstructure is dependent
on the pressing speed, because recovery occurs more easily at the slower speeds, so that the microstructure is then more equilibrated.
There is also indirect evidence for the advent of frictional effects when the cross-sectional dimensions of the samples are
at or below ∼5 mm. 相似文献
5.
Sang H. Kim Nack J. Kim H. H. Chung Sung G. Pyo S. J. Hwang 《Metallurgical and Materials Transactions A》1998,29(9):2273-2283
The present study is concerned with γ-(Ti52Al48)100−x
B
x
(x=0, 0.5, 2, 5) alloys produced by mechanical milling/vacuum hot pressing (VHPing) using melt-extracted powders. Microstructure
of the as-vacuum hot pressed (VHPed) alloys exhibits a duplex equiaxed microstructure of α2 and γ with a mean grain size of 200 nm. Besides α2 and γ phases, binary and 0.5 pct B alloys contain Ti2AlN and Al2O3 phases located along the grain boundaries and show appreciable coarsening in grain and dispersoid sizes during annealing
treatment at 1300 °C for 5 hours. On the other hand, 2 pct B and 5 pct B alloys contain fine boride particles within the γ
grains and show minimal coarsening during annealing. Room-temperature compressing tests of the as-VHPed alloys show low ductility,
but very high yield strength >2100 MPa. After annealing treatment, mechanically milled alloys show much higher yield strength
than conventional powder metallurgy and ingot metallurgy processed alloys, with equivalent ductility to ingot metallurgy processed
alloys. The 5 pct B alloy with the smallest grain size shows higher yield strength than binary alloy up to the test temperature
of 700 °C. At 850 °C, 5 pct B alloy shows much lower strength than the binary alloy, indicating that the deformation of fine
5 pct B alloy is dominated by the grain boundary sliding mechanism.
This article is based on a presentation made in the symposium “Mechanical Behavior of Bulk Nanocrystalline Solids,” presented
at the 1997 Fall TMS Meeting and Materials Week, September 14–18, 1997, in Indianapolis, Indiana, under the auspices of the
Mechanical Metallurgy (SMD), Powder Materials (MDMD), and Chemistry and Physics of Materials (EMPMD/SMD) Committees. 相似文献
6.
The super α
2 Ti3Al-based alloy with a fine grain size of ∼2.2 μm exhibits superplastic elongations over 1000 pct at 920 °C to 1000 °C, 600 pct at 900 °C, 330 pct at 850 °C, and 140 pct
at 750 °C. Mechanical anisotropy is observed in this alloy, and relatively lower flow stresses and higher tensile elongations
are obtained in the 45 deg specimen loaded at 25 °C to 960 °C. The texture characteristics appear to impose significant influence
on the mechanical anisotropy at temperatures below 900 °C (under the dislocation creep condition), and the {111}〈2
〉 and {0001} basal textures evolve in the β and α
2 phases after tensile straining. At loading temperatures higher than 900 °C (under the superplastic flow condition), the anisotropy
effect is less pronounced and the grain orientation distribution becomes basically random in nature. Rationalizations for
the mechanical anisotropy in terms of the Schmid factor calculations for the major and minor texture components in the β and α
2 phases provide consistent explanations for the deformation behavior at lower temperatures as well as the initial straining
stage at higher temperatures. 相似文献
7.
Dong H. Shin Ki S. Kim Dong W. Kum Soo W. Nam 《Metallurgical and Materials Transactions A》1990,21(10):2729-2737
Thermomechanical processes were developed which give fine grain sizes of 6 and 8 μm in the 7475 Al alloy. Superplastic properties
of this material were evaluated in the temperature range of 400 °C to 545 °C over the strain-rate range of 2.8 x 10-4 to 2.8 X 10-2 s-1. The maximum ductility exhibited by the alloy was approximately 2000 pct, and optimum superplasticity was achieved at a strain
rate of 2.8 X 10-3 s-1 which is higher by an order of magnitude than other 7475 Al alloys. This result is attributed to the presence of fine dispersoids
which maintain the fine grain size at high homologous temperatures. The flow stress and strain-rate sensitivity strongly depend
on the grain size. The superplastic 7475 Al alloy has strain-rate sensitivities of 0.67 (6 μm) and 0.5 (13 μm) and an activation
energy which is similar to the one for grain boundary diffusion of aluminum. Microstructural investigation after superplastic
tests revealed zones free of dispersoid particles at grain boundaries primarily normal to the tensile direction. These dispersoidfree
zones (DFZs) appear even after 100 pct elongation and are occasionally as large as 5 μm across. This result demonstrates the
importance of diffusional flow in superplastic deformation of the fine-grained 7475 Al alloy especially at low elongations. 相似文献
8.
Shogo Komura Zenji Horita Minoru Furukawa Minoru Nemoto Terence G. Langdon 《Metallurgical and Materials Transactions A》2001,32(3):707-716
An Al-3 pct Mg-0.2 pct Sc alloy was fabricated by casting and subjected to equal-channel angular pressing to reduce the grain
size to ∼0.2 μm. Very high tensile elongations were achieved in this alloy at temperatures over the range from 573 to 723 K, with elongations
up to >2000 pct at temperatures of 673 and 723 K and strain rates at and above 10−2 s−1. By contrast, samples of the same alloy subjected to cold rolling (CR) yielded elongations to failure of <400 pct at 673
K. An analysis of the experimental data for the equal-channel angular (ECA)-pressed samples shows consistency with conventional
superplasticity including an activation energy for superplastic flow which is within the range anticipated for grain boundary
diffusion in pure Al and interdiffusion in Al-Mg solid solution alloys. 相似文献
9.
Z. Y. Ma R. S. Mishra M. W. Mahoney R. Grimes 《Metallurgical and Materials Transactions A》2005,36(6):1447-1458
The effect of friction stir processing on the superplastic behavior of extruded Al-4Mg-1Zr was examined at 350 °C to 600 °C
and at initial strain rates of 1×10−3 to 1 s−1. A combination of a fine grain size of 1.5 μm and high-angle grain boundaries in the friction stir-processed (FSP) alloy led to considerably enhanced superplastic ductility,
much-reduced flow stress, and a shift to a higher optimum strain rate and lower optimum temperature. The as-extruded alloy
exhibited the highest superplastic ductility of 1015 pct at 580 °C and an initial strain rate of 1×10−2s−1, whereas a maximum elongation of 1280 pct was obtained at 525 °C and an initial strain rate of 1×10−1s−1 for the FSP alloy. The FSP alloy exhibited enhanced superplastic deformation kinetics compared to that predicted by the constitutive
relationship for superplasticity in fine-grained aluminum alloys. A possible origin for enhanced superplastic deformation
kinetics in the FSP condition is proposed. 相似文献
10.
Seung-Ho Mun Masashi Watanabe David B. Williams Xingyi Li Kyu Hwan Oh Hu-Chul Lee 《Metallurgical and Materials Transactions A》2002,33(4):1057-1067
Precipitation of austenite particles at grain and lath boundaries after aging treatment of a Fe-8Mn-7Ni alloy was investigated
by selected area electron diffraction (SAD), X-ray energy dispersive spectrometry (EDS) in a scanning transmission electron
microscope (STEM), and high-resolution (HRTEM) analysis. High spatial-resolution (2 to 5 nm) EDS analysis revealed no significant
segregation of alloying elements at grain boundaries but the precipitation of very fine particles of Mn- and Ni-rich phase.
Detailed EDS, SAD, and HRTEM analyses all confirmed that these particles are austenite phase, which have a Kurdjumov-Sachs
(K-S) orientation relationship with one of the adjacent grain. The concentration of Mn and Ni in austenite, measured by EDS,
varied from ∼15 pct to a maximum of ∼30 pct. Low-voltage scanning electron microscopy (SEM) fractographs also revealed the
presence of very fine, second-phase precipitates on the fracture surface of the embrittled alloys. 相似文献
11.
Yuichi Miyahara Kiyoshi Matsubara Zenji Horita Terence G. Langdon 《Metallurgical and Materials Transactions A》2005,36(7):1705-1711
The extrusion/equal channel angular pressing (EX-ECAP) processing procedure, in which magnesium-based alloys are subjected
to extrusion followed by ECAP, was applied to a Mg-7.5 pct Al-0.2 pct Zr alloy prepared by casting. Microstructural inspection
showed the EX-ECAP process was effective in reducing the grain size from ∼21 μm after extrusion to an as-pressed grain size of ∼0.8 μm. It is shown through static annealing that these ultrafine grains are reasonably stable up to 473 K, but grain growth occurs
at higher temperatures. Tensile specimens were cut from the billets prepared by EX-ECAP and testing showed these specimens
exhibited superplasticity at relatively low temperatures with maximum elongations up to >700 pct. By processing through EX-ECAP
to a higher imposed strain and thereby increasing the area fraction of high-angle boundaries, it is demonstrated that there
is a potential for achieving high-strain-rate superplasticity.
This article is based on a presentation made at the Symposium entitled “Phase Transformations and Deformation in Magnesium
Alloys,” which occurred during the Spring TMS meeting, March 14–18, 2004, in Charlotte, NC, under the auspices of the ASM-MSCTS
Phase Transformations Committee. 相似文献
12.
A metallographic study of the porosity and fracture behavior in unidirectionally solidified end chill castings of 319.2 aluminum
alloy (Al-6.2 pct Si-3.8 pct Cu-0.5 pct Fe-0.14 pct Mn-0.06 pct Mg-0.073 pct Ti) was carried out using optical microscopy
and scanning electron microscopy (SEM) to determine their relationship with the tensile properties. The parameters varied
in the production of these castings were the hydrogen (∼0.1 and ∼0.37 mL/100 g Al), modifier (0 and 300 ppm Sr), and grain
refiner (0 and 0.02 wt pct Ti) concentrations, as well as the solidification time, which increased with increasing distance
from the end chill bottom of the casting, giving dendrite arm spacings (DASs) ranging from ∼15 to ∼95 /im. Image analysis
and energy dispersive X-ray (EDX) analysis were employed for quantification of porosity/microstructural constituents and fracture
surface analysis (phase identification), respectively. The results showed that the local solidification time(viz. DAS) significantly influences the ductility at low hydrogen levels; at higher levels, however, hydro-gen has a more pronounced
effect (porosity related) on the drop in ductility. Porosity is mainly observed in the form of elongated pores along the grain
boundaries, with Sr increasing the porosity volume percent and grain refining increasing the probability for pore branching.
The beneficial effect of Sr modification, however, improves the alloy ductility. Fracture of the Si, β-Al5FeSi, α- Al15(Fe,Mn)3Si2, and Al2Cu phases takes place within the phase particles rather than at the particle/Al matrix interface. Sensitivity of tensile properties
to DAS allows for the use of the latter as an indicator of the expected properties of the alloy. 相似文献
13.
A. K. Aiyangar B. W. Neuberger P. G. Oberson S. Ankem 《Metallurgical and Materials Transactions A》2005,36(3):637-644
Ambient (room) temperature studies have been carried out on an α-Ti-1.6 wt pct V alloy to determine the effects of stress level and grain size on ambient temperature creep behavior. Creep
tests were performed at five different stress levels ranging from 75 to 95 pct of the yield stress value on specimens with
an average grain size of 226 μm. It has been found that the alloy exhibits appreciable creep at stress levels far below the yield stress, with creep occurring
at values as low as 75 pct of the yield stress. The extent of creep strain was found to decrease with a decrease in stress
level. Creep tests were also performed on this alloy with different grain sizes ranging from 38 to 226 μm at a stress level of 90 pct of the yield stress. It was seen that the extent of creep strain decreased with a decrease in
grain size. Fine slip and time-dependent twinning were found to be the creep deformation mechanisms. Based on the results
of this investigation and earlier studies, it is suggested that time-dependent twinning is a major creep deformation mechanism
in α-titanium alloys that contain small amounts of alloying elements. The time-dependent twinning phenomenon has been attributed
to the diffusion of oxygen away from the twin-matrix interface, permitting the growth of twins. 相似文献
14.
Fe-37.3 wt pct Ni-3.6 wt pct Al-3.3 wt pct Ti-0.2 wt pct C alloy, which reveals an excellent combination of high strength
and good elongation endowed by formation of homogeneously dispersed fine γ′ precipitates in the matrix during aging at 823 K, has been investigated by means of transmission electron and optical microscopies,
electron diffractions, and tensile tests. The influence of unique γ′+α cellular products on the mechanical properties has also been studied. Because of low elastic mismatch between the austenitic
γ matrix and isomorphic γ′ precipitate phases, the homogeneously distributed precipitate particles, which formed at the early stage of aging, were
observed to persist even after long-term aging. After very lengthy aging, the fine γ′ phase particles were changed to coarser γ′ lamellae at the grain boundary reaction front, which were alternately arranged with fine α lamellae that were estimated to have been transformed from the austenite-stabilizing-solute(Ni, C)-depleted γ lamellae. The fine duplex γ′+α cellular product did not affect deleteriously the room-temperature tensile properties of the alloy. However, the cellular
structure was observed to cause the grain boundary embrittlement of the aged alloy at elevated temperatures higher than 681
K. 相似文献
15.
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
16.
Zhihong Zhong Yuefeng Gu Yong Yuan Toshio Osada Chuanyong Cui Tadaharu Yokokawa Toshimitsu Tetsui Hiroshi Harada 《Metallurgical and Materials Transactions A》2012,43(3):1017-1025
The influence of solution temperature on the microstructure and mechanical properties of TMW-4M3 superalloy has been investigated.
Comparisons of mechanical properties have also been made between the heat-treated TMW-4M3 variants and the commercial U720Li.
The key microstructural variables examined were grain size and the volume fraction and size of the strengthening γ′ precipitates that control the mechanical properties of these alloys. By increasing the solution temperature from 1373 K
to 1393 K (1100 °C to 1120 °C), the volume fraction of primary gamma prime dropped from 16.9 pct to 14.5 pct, whereas the
average grain size increased from 8.7 μm to 10.6 μm. Compared with an alloy with a smaller grain size, the alloy with a larger grain size exhibited superior resistances to
creep and fatigue crack growth without the expense of reduced tensile strength and low-cycle fatigue resistance. This suggested
that a higher solution temperature may benefit TMW-4M3 in terms of superior overall properties. The greater overall properties
of TMW-4M3 variants than that of commercial U720Li were also demonstrated experimentally. The possible explanations for the
improvement of mechanical properties were discussed. 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.
J. X. Dong P. A. Karnezis G. Durrant B. Cantor 《Metallurgical and Materials Transactions A》1999,30(5):1341-1356
This article describes the results of an investigation into the microstructure and mechanical properties of a gravity die
cast and direct squeeze cast LM25 alloy (Al-7Si-0.3Mg-0.3Fe). The direct squeeze cast LM25 alloy has superior mechanical properties
compared to the gravity die cast LM25 alloy, especially with regard to ductility, which is increased from ∼1.7 pct for the
gravity die cast LM25 alloy to ∼8.0 pct for the direct squeeze cast LM25 alloy in the T6 heat-treated condition. This increase
in ductility is due to (1) the removal of porosity, (2) a decrease in Si particle size, and (3) a refinement of the Fe-Si-aluminide
particles. High cooling rates in direct squeeze casting result in quench modification of the Si particles, such that chemical
modification with Sr or Na may not be required. In addition, direct squeeze casting is more tolerant of Fe impurities in the
alloy, due to the formation of smaller Fe-Si-aluminide particles than those in gravity die cast material. The direct squeeze
cast LM25+Fe alloy (Al-7Si-0.3Mg-1.0Fe) has a ductility of ∼6.5 pct, compared to that of ∼0.5 pct for the gravity die cast
LM25 + Fe alloy in the T6 heat-treated condition. This increase in tolerance to Fe impurities can lead to a substantial reduction
in manufacturing costs due to (1) reduced raw-material costs, (2) reduced die sticking, and (3) improved die life. 相似文献
19.
Transition of dominant diffusion process during superplastic deformation in AZ61 magnesium alloys 总被引:2,自引:0,他引:2
The superplastic behavior of the AZ61 magnesium alloy sheet, processed by one-step hot extrusion and possessing medium grain
sizes of ∼12 μm, has been investigated over the temperature range of 523 to 673 K. The highest superplastic elongation of
920 pct was obtained at 623 K and a deformation rate of 1×10−4 s−1. In the lower and higher strain rate regimes, with apparent m values of ∼0.45 and ∼0.25, respectively, grain-boundary sliding (GBS) and dislocation creep appeared to dominate the deformation,
consistent with the scanning electron microscopy (SEM) examination. The SEM examination also revealed that individual GBS
started to operate from the very initial deformation stage in the strain rate range with m∼0.45, which was attributed to the relatively high fraction (88 pct) of high-angle boundaries. The analyses of the superplastic
data over 523 to 673 K and 5×10−5 to 1×10−3 s−1 revealed a true stress exponent of ∼2, and the activation energy was close to that for grain-boundary and lattice diffusion
of magnesium at 523 to 573 K and 573 to 673 K, respectively. The transition temperature of activation energy is ∼573 K, which
is attributed to the change in the dominant diffusion process from grain-boundary diffusion to lattice diffusion. It is demonstrated
that the effective diffusion coefficient is a valid parameter to characterize the superplastic behavior and the dominant diffusion
process. 相似文献
20.
Shogo Komura Zenji Horita Minoru Furukawa Minoru Nemoto Terence G. Langdon 《Metallurgical and Materials Transactions A》2001,32(13):707-716
An Al-3 pct Mg-0.2 pct Sc alloy was fabricated by casting and subjected to equal-channel angular pressing to reduce the grain
size to ∼0.2 μm. Very high tensile elongations were achieved in this alloy at temperatures over the range from 573 to 723
K, with elongations up to >2000 pct at temperatures of 673 and 723 K and strain rates at and above 10−2 s−1. By contrast, samples of the same alloy subjected to cold rolling (CR) yielded elongations to failure of <400 pct at 673
K. An analysis of the experimental data for the equal-channel angular (ECA)—pressed samples shows consistency with conventional
superplasticity including an activation energy for superplastic flow which is within the range anticipated for grain boundary
diffusion in pure Al and interdiffusion in Al−Mg solid solution alloys.
MINORU NEMOTO, formerly Professor, Department of Materials Science and Engineering, Faculty of Engineering, Kyushu University. 相似文献