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1.
Creep behavior of AZ31 magnesium alloy in low temperature range between 423 K and 473 K 总被引:1,自引:0,他引:1
The deformation behavior of coarse-grained AZ31 magnesium alloy was examined in creep at low temperatures below 0.5 T
m and low strain rates below 5 × 10−4 s−1. The creep test was conducted in the temperature range between 423 and 473 K (0.46–0.51 T
m) under various constant stresses covering the strain rate range 5 × 10−8 s−1–5 × 10−4 s−1. All of the creep curves exhibited two types depending on stress level. At low stress (σ/G < 4 × 103), the creep curve was typical of class I behavior. However, at high stresses (σ/G > 4 × 103), the creep curve was typical of class II. At the low stress level, deformation could be well described by solute drag creep
whereas at the high stress level, deformation could be well described by dislocation climb creep associated with pipe diffusion
or lattice diffusion. The transition of deformation mechanism from solute drag creep to dislocation climb creep, on the other
hand, could be explained in terms of solute-atmosphere-breakaway concept. 相似文献
2.
Compressive experiments on three types of rigid polyurethane foams were conducted by employing modified split Hopkinson pressure
bars (SHPBs). The foam materials, which were based on polymethylene diisocyanate (PMDI), varied only in density (0.31 × 103, 0.41 × 103, and 0.55 × 103 kg/m3) and were compressed at strain rates as high as 3 × 103 s−1. Dynamic experiments were also performed on these three foam materials at temperatures ranging from 219 to 347 K, while maintaining
a fixed high strain rate of ~3 × 103 s−1. In addition, an MTS materials testing frame was used to characterize the low-strain-rate compressive response of these three
foam materials at room temperature (295 K). Our study determined the effects of density, strain rate, and temperature on the
compressive response of the foam materials, resulting in a compressive stress–strain curve for each material. 相似文献
3.
Welbert Ribeiro Calado Odair José dos Santos Cynthia Serra Batista Castro Ronaldo Neves Barbosa Berenice Mendonça Gonzalez 《Journal of Materials Science》2008,43(17):6005-6011
The influence of finishing rolling temperature (FRT) on dynamic strain aging (DSA) behavior and high-temperature resistance
of a fire resistant steel microalloyed with Mo and Nb was investigated by means of tensile tests performed at temperatures
ranging from 25 to 600 °C and strain rates of 10−4 to 10−1 s−1. In these steels, DSA manifestations are less intense than those observed for carbon steels and they take place at higher
temperatures. The precipitation behavior of the steels was also considered. Hardness of samples heat treated at 100–600 °C
displayed a maximum at 400 °C. Samples treated at this temperature and tensile tested at 600 °C did not show a higher yield
stress than the untreated specimens. Results obtained indicated that DSA in the fire resistant steel might have a contribution
for its fire resistance. The empirical activation energies related to the appearance of serrations on the stress–strain curves
and to the maxima on the variation of tensile strength with temperature suggested that the high-temperature strengthening
associated with DSA in this steel is the dynamic interaction of interstitial-substitutional solute dipoles and dislocations.
The steel with lower FRT is more susceptible to DSA because of its higher amount of carbon in solid solution and showed better
results in terms of high-temperature resistance. 相似文献
4.
V. I. Dybkov V. G. Khoruzha V. R. Sidorko K. A. Meleshevich A. V. Samelyuk D. C. Berry K. Barmak 《Journal of Materials Science》2009,44(22):5960-5979
Dissolution kinetics of cobalt in liquid 87.5%Sn–7.5%Bi–3%In–1%Zn–1%Sb and 80%Sn–15%Bi–3%In–1%Zn–1%Sb soldering alloys and
phase formation at the cobalt–solder interface have been investigated in the temperature range of 250–450 °C. The temperature
dependence of the cobalt solubility in soldering alloys was found to obey a relation of the Arrhenius type c
s = 4.06 × 102 exp (−46300/RT) mass% for the former alloy and c
s = 5.46 × 102 exp (−49200/RT) mass% for the latter, where R is in J mol−1 K−1 and T in K. For tin, the appropriate equation is c
s = 4.08 × 102 exp (−45200/RT) mass%. The dissolution rate constants are rather close for these soldering alloys and vary in the range (1–9) × 10−5 m s−1 at disc rotational speeds of 6.45–82.4 rad s−1. For both alloys, the CoSn3 intermetallic layer is formed at the interface of cobalt and the saturated or undersaturated solder melt at 250 °C and dipping
times up to 1800 s, whereas the CoSn2 intermetallic layer occurs at higher temperatures of 300–450 °C. Formation of an additional intermetallic layer (around 1.5 μm
thick) of the CoSn compound was only observed at 450 °C and a dipping time of 1800 s. A simple mathematical equation is proposed
to evaluate the intermetallic-layer thickness in the case of undersaturated melts. The tensile strength of the cobalt-to-solder
joints is 95–107 MPa, with the relative elongation being 2.0–2.6%. 相似文献
5.
Wubian Tian ZhengMing Sun Hitoshi Hashimoto Yulei Du 《Journal of Materials Science》2009,44(1):102-107
The compressive properties of ternary compound Cr2AlC at different temperatures and strain rates were studied. When tested at a strain rate of 5.6 × 10−4 s−1, the compressive strength decreases continuously from 997 ± 29 MPa at room temperature to 523 ± 7 MPa at 900 °C. The ductile-to-brittle
transition temperature is measured to be in the range of 700 to 800 °C. When tested in the strain rate range of 5.6 × 10−5 to 5.6 × 10−3 s−1, Cr2AlC fails in a brittle mode at room temperature, whereas the deformation mode changes from a brittle to a ductile as the strain
rate is lower than 5.6 × 10−4 s−1 when compressed at 800 °C. The compressive strength increases slightly with increasing strain rate at room temperature and
it is less dependent on strain rate when tested at 800 °C. The plastic deformation mechanism of Cr2AlC was discussed in terms of dislocation-related activities, such as kink band formation, delamination, decohesion of grain
boundary, and microcrack formation. 相似文献
6.
The superplastic behavior of cast and hot-extruded NiAl–28Cr–6Mo is observed in the strain rates between
= 1.04 × 10−3 and 5.02 × 10−2 s−1 at 1323–1373 K. The synchronous operation of dislocation glide and dynamic recovery is responsible for the tested alloy to
exhibit superplastic behavior. 相似文献
7.
Masataka Hakamada Kazunori Shimizu Tomokazu Yamashita Akira Watazu Naobumi Saito Hajime Iwasaki 《Journal of Materials Science》2010,45(3):719-724
Two cast noncombustible Mg–9Al–1Zn–1Ca alloys (composition in mass%) with coarse and fine initial microstructures were hot
forged by compression at temperatures of 523–603 K and a true strain rate of 1–10−2 s−1. The compressive stress–strain curves for the two alloys were similar and typical of metals undergoing dynamic recrystallization
(DRX). The alloy with the coarse initial microstructure suffered from edge crack formation during hot forging, while the alloy
with the fine initial microstructure exhibited smooth peripheral surfaces after hot forging at temperatures of 573 K and above.
The reduction of grain size by DRX was similar in the two hot-forged alloys, but the recrystallized volume fraction was lower
in the alloy with the coarse initial microstructure. Insoluble second phases (seemingly Al2Ca) provide additional DRX sites, and thus it is expected that the finer initial cast microstructure will improve the microstructure
in the resulting hot-forged Mg parts. 相似文献
8.
Compressive tests of polycrystalline Ti3SiC2 were performed from room temperature to 1423 K at strain rates of 1×10–4 s–1 and 2.5×10–5 s–1, respectively. The effect of strain rates on high-temperature compressive property was also investigated. Polycrystalline
Ti3SiC2 exhibited positive temperature dependence of flow stress (flow stress anomaly) and showed a temperature peak at 1173 K. The
brittle-to-ductile transition temperature (BDTT) for polycrystalline Ti3SiC2 was strain-rate sensitive, an approximately 100 K decrease in transition temperature was associated with four times of magnitude
decrease in strain rate. In addition, the fracture morphology changed from predominately intergranular to mostly transgranular.
The mechanism responsible for the brittle-to-ductile transition in Ti3SiC2 was involved in the onset of a thermally activated deformation process.
Received: 6 July 1999 / Reviewed and accepted: 9 August 1999 相似文献
9.
Tensile tests were performed on high-purity W and Mo polycrystals at room temperature for a range of axial strain-rates 2.1 × 10−4–2.1 × 10−2 s−1. The critical resolved shear stress (CRSS) data was analyzed by using the analytical formulation for the strain-rate dependence
of the CRSS derived in the kink-pair nucleation (KPN) model of flow stress in crystals with high intrinsic lattice friction.
On evaluation of various microscopic slip-parameters of the model, the active slip-system in both W and Mo polycrystals was
identified as {110}〈111〉. This is in good agreement with that deduced from the published data on the temperature dependence
of the CRSS of these crystals as well as from the observed slip-lines on the deformed crystals reported in the literature.
Moreover, the available data on the temperature dependence of the CRSS of Mo, Nb, Fe, V, and K crystals were also analyzed
within the framework of the KPN model of flow stress. Peierls mechanism was found to be responsible for the CRSS of these
metals; the active slip-systems in refractory metals Mo, Nb, Fe, and V were {110}〈111〉 and {211}〈111〉 whereas that in alkali
metal K was {321}〈111〉. 相似文献
10.
The hot deformation behavior of Al 2024 was studied by isothermal hot compression tests in the temperature range of 250–500 °C
and strain rate range of 10−3 to 102 s−1 in a computer-controlled 50 kN servo-hydraulic universal testing machine (UTM). The results show that the flow stress of
Al 2024 alloy increases with strain rate and decreases after a peak value, indicating dynamic recovery and recrystallization.
The processing map exhibits two domains of optimum efficiency for hot deformation at different strains, including the low
strain rate domain at 500 °C and between 10−2 and 10−1 s−1 and the high strain rate domain in 250 and 300 °C in the strain rate range of 101 to 102 s−1. An attempt has been made in this article to generate a new hybrid 4D process map which illustrates contours of power dissipation
and instability in the 3D space of strain rate, temperature, and strain. 相似文献
11.
Kaixuan Wang Weidong Zeng Yongqing Zhao Yunjin Lai Yigang Zhou 《Journal of Materials Science》2010,45(21):5883-5891
Isothermal compression of Ti-17 titanium alloy with lamellar starting structure at the deformation temperatures ranging from
780 °C to 860 °C, the strain rates ranging from 0.001 to 10 s−1, and the height reductions ranging from 15% to 75% with an interval 15% were carried out. Based on experimental results,
3-D processing maps including strain were developed and used to identify various microstructural mechanisms and distinguish
the safe and unsafe domains. The processing maps exhibit two maximum power dissipation efficiency domains and dynamic globularization
takes place in this two domains. The first domain occurs at 800–860 °C and at strain rates lower than 0.01 s−1, and the second occurs at 780–800 °C and at strain rates lower than 0.01 s−1. With the increasing of the strains, the values of maximum power dissipation efficiency in this two domains increase. One
flow instability domain due to adiabatic shear bands and lamellar kinking occurs at strain rates higher than 0.487 s−1, lower temperature, and higher strain above 0.2. The instability deformation region increases with increasing strain, strain
rate, and decreasing temperature. 相似文献
12.
Jingqi Zhang Hongshuang Di Hongtao Wang Kun Mao Tianjun Ma Yu Cao 《Journal of Materials Science》2012,47(9):4000-4011
The hot deformation behavior of Ti-15-3 titanium alloy was investigated by hot compression tests conducted in the temperature
range 850–1150 °C and strain rate range 0.001–10 s−1. Using the flow stress data corrected for deformation heating, the activation energy map, processing maps and Zener–Hollomon
parameter map were developed to determine the optimum hot-working parameters and to investigate the effects of strain rate
and temperature on microstructural evolution of this material. The results show that the safe region for hot deformation occurs
in the strain rate range 0.001–0.1 s−1 over the entire temperature range investigated. In this region, the activation energy is ~240 ± 5 kJ/mol and the ln Z values vary in range of 13.9–21 s−1. Stable flow is associated with dynamic recovery and dynamic recrystallization. Also, flow instabilities are observed in
the form of localized slip bands and flow localization at strain rates higher than 0.1 s−1 over a wide temperature range. The corresponding ln Z values are larger than 21 s−1. The hot deformation characteristic of Ti-15-3 alloy predicted from the processing maps, activation energy map, and Zener–Hollomon
parameter map agrees well with the results of microstructural observations. 相似文献
13.
O. N. Senkov J. M. Scott S. V. Senkova F. Meisenkothen D. B. Miracle C. F. Woodward 《Journal of Materials Science》2012,47(9):4062-4074
Compression properties of a refractory multi-component alloy, Ta20Nb20Hf20Zr20Ti20, were determined in the temperature range of 296–1473 K and strain rate range of 10−1–10−5 s−1. The properties were correlated with the microstructure developed during compression testing. The alloy was produced by vacuum
arc melting, and it was hot isostatically pressed (HIPd) and homogenized at 1473 K for 24 h prior to testing. It had a single-phase
body-centered cubic structure with the lattice parameter a = 340.4 pm. The grain size was in the range of 100–200 μm. During compression at a strain rate of έ = 10−3 s−1, the alloy had the yield strength of 929 MPa at 296 K, 790 MPa at 673 K, 675 MPa at 873 K, 535 MPa at 1073 K, 295 MPa at
1273 K and 92 MPa at 1473 K. Continuous strain hardening and good ductility (ε ≥ 50%) were observed in the temperature range
from 296 to 873 K. Deformation at T = 1073 K and έ ≥ 10−3 s−1 was accompanied by intergranular cracking and cavitation, which was explained by insufficient dislocation and diffusion mobility
to accommodate grain boundary sliding activated at this temperature. The intergranular cracking and cavitation disappeared
with an increase in the deformation temperature to 1273 and 1473 K or a decrease in the strain rate to ~10−5 s−1. At these high temperatures and/or low-strain rates the alloy deformed homogeneously and showed steady-state flow at a nearly
constant flow stress. Partial dynamic recrystallization, leading to formation of fine equiaxed grains near grain boundaries,
was observed in the specimens deformed at 1073 and 1273 K and completed dynamic recrystallization was observed at 1473 K. 相似文献
14.
Megumi Kawasaki Anibal de A. Mendes Vitor L. Sordi Maurizio Ferrante Terence G. Langdon 《Journal of Materials Science》2011,46(1):155-160
Experiments were conducted on a Pb-62% Sn eutectic alloy containing 160 ppm of Sb. The alloy was processed by equal-channel
angular pressing (ECAP) through 1 to 5 passes at room temperature and then tested in tension at a temperature of 423 K using
initial strain rates from 1.0 × 10−4 to 1.0 × 10−1 s−1. Excellent superplastic elongations were achieved at intermediate strain rates with a maximum elongation to failure of 2,665%.
It is shown that, for processing through similar numbers of ECAP passes, these elongations are higher than in an earlier investigation
using a Pb-62% Sn alloy of higher purity. The results are presented pictorially in the form of a deformation mechanism map
by plotting normalized grain size against normalized stress at a temperature of 423 K. 相似文献
15.
D. E. Sefton M. A. Rist S. Gungor 《Journal of Materials Science: Materials in Electronics》2009,20(11):1083-1089
Compression experiments on bulk Sn-3.5Ag lead-free solder specimens have been carried out to help formulate the material constitutive
behaviour of this alloy using the concept of an evolving internal stress. Tests covered the temperature range 0–125 °C and
fixed strain rates between 3 × 10−7–3 × 10−3 s−1. Flow behaviour was found to be compatible with that for a deforming a tin-rich matrix (stress exponent n = 7, activation energy Q = 46.7 kJ/mol) in which the external applied stress is reduced by an internal back stress due to the presence of precipitate
phase particles. Stress–strain curves have been satisfactorily modelled using rate equations incorporating linear hardening
and diffusion-controlled recovery. Comparison with supplementary tension and creep experiments, and with data from other researchers,
indicates that inconsistencies in reported flow behaviour is most likely to be due to variations in initial microstructure
rather than the nature of the applied loading. 相似文献
16.
In this article, results of the measurements of the longitudinal and transverse wave velocities in steel have been presented
as a function of temperature. The conducted tests involved two types of corrosion-resistant steel: X14CrMoS17 and X90CrMoV18.
The tests were based on the ultrasonic wave transition method using transducers operating at 5.4 MHz for the longitudinal
wave and 3.2 MHz for the transverse wave. Measurements of the wave velocity were taken at temperatures from 293 K to 1,173 K.
The longitudinal wave velocity in X14CrMoS17 steel varies from 6,002 m·s−1 at 293 K to 5,115 m·s−1 at 1,173 K, while the velocity in the X90CrMoV18 steel changes from 5,975 m·s−1 at 293 K to 5,381 m·s−1 at 1,023 K. The transverse wave velocities vary from 3,239 m·s−1 at 293 K to 2,449 m·s−1 at 1,173 K in X14CrMoS17 steel, and from 3,251 m·s−1 at 293 K to 2,478 m·s−1 at 1,173 K in X90CrMoV18 steel. The obtained results represented a basis for determination of the properties of the steels
examined, such as Young’s modulus, Poisson’s ratio, Helmholtz’s modulus of volume elasticity, or Lame’s constants. The results
have been verified by comparing the Young’s modulus obtained with the values corresponding to individual steel grades and
temperatures (293 K, 373 K, 473 K, 573 K, and 673 K) obtained by traditional methods of measuring mechanical properties as
provided in PN-EN 10088-1:2007. The results of this comparison confirmed the reliability of the conducted investigation. 相似文献
17.
New NASICON type materials of composition, Li3−2x
Al2−x
Sb
x
(PO4)3 (x = 0·6 to 1·4), have been prepared and characterized by powder XRD and IR. D.C. conductivities were measured in the temperature
range 300–573 K by a two-probe method. Impedance studies were carried out in the frequency region 102−106 Hz as a function of temperature (300–573 K). An Arrhenius behaviour is observed for all compositions by d.c. conductivity
and the Cole-Cole plots obtained from impedance data do not show any spikes on the lower frequency side indicating negligible
electrode effects. A maximum conductivity of 4·5 × 10−6 S cm−1 at 573 K was obtained for x = 0·8 of the Li3−2x
Al2−x
Sb
x
(PO4)3 system. 相似文献
18.
Serrated flow in a Ni–Co–Cr-base superalloy was studied in three microstructural conditions (SUB, SUBA, and SUPER) from 25
to 750 °C by tensile test at initial strain rates ranging from 8 × 10−5 to 3 × 10−3 s−1. The results showed that the SUB and SUBA samples had fine grain size of about 9 μm, whereas the SUPER samples had coarse
grain size of about 600 μm. The tertiary γ′ fraction was about 0 in the SUB, 5% in the SUBA, and 15% in the SUPER samples,
respectively. The types and temperature ranges of serration were different in the alloy with SUB, SUBA, and SUPER microstructures.
It is proposed that the tertiary γ′ fraction and size had great effects on the serrated flow of the alloy with different microstructures. 相似文献
19.
Room temperature tensile test results of solution annealed 304 stainless steel at strain rates ranging between 5 × 10−4 and 1 × 10−1 s−1 reveal that with increase in strain rate yield strength increases and tensile strength decreases, both maintaining power–law
relationships with strain rate. The decrease in tensile strength with increasing strain rate is attributed to the lesser amount
of deformation-induced martensite formation and greater role of thermal softening over work hardening at higher strain rates.
Tensile deformation of the steel is found to occur in three stages. The deformation transition strains are found to depend
on strain rate in such a manner that Stage-I deformation (planar slip) is favoured at lower strain rate. A continuously decreasing
linear function of strain rate sensitivity with true strain has been observed. Reasonably good estimation for the stress exponent
relating dislocation velocity and stress has been made. The linear plot of reciprocal of strain rate sensitivity with true
strain suggests that after some critical amount of deformation the increased dislocation density in austenite due to the formation
of some critical amount of deformation-induced martensite plays important role in carrying out the imposed strain rate. 相似文献
20.
Ehab A. El-Danaf Abdulhakim A. AlMajid Mahmoud S. Soliman 《Journal of Materials Science》2008,43(18):6324-6330
High-temperature tensile deformation of 6082-T4 Al alloy was conducted in the range of 623–773 K at various strain rates in
the range of 5 × 10−5 to 2 × 10−2 s−1. Stress dependence of the strain rate revealed a stress exponent, n of 7 throughout the ranges of temperatures and strain rates tested. This stress exponent is higher than what is usually observed
in Al–Mg alloys under similar experimental conditions, which implies the presence of threshold stress. This behavior results
from dislocation interaction with second phase particles (Mg2Si). The experimental threshold stress values were calculated, based on the finding that creep rate is viscous glide controlled,
based on creep tests conducted on binary Al–1Mg at 673 K, that gave n a value of 3. The threshold stress (σ
o) values were seen to decrease exponentially with temperature. The apparent activation energy for 6082-T4 was calculated to
be about 245 kJ mol−1, which is higher than the activation energy for self-diffusion in Al (Q
d = 143 kJ mol−1) and for the diffusion of Mg in Al (115–130 kJ mol−1). By incorporating the threshold stress in the analysis, the true activation energy was calculated to be about 107 kJ mol−1. Analysis of strain rate dependence in terms of the effective stress (σ − σ
o) using normalized parameters, revealed a single type of deformation behavior. A plot of normalized strain rate () versus normalized effective stress (σ − σ
o)/G, on a double logarithmic scale, gave an n value of 3.
Ehab A. El-Danaf—on leave from the Department of Mechanical Design and Production, College of Engineering, Cairo University,
Egypt. 相似文献