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1.
S. G. Sandomirskii 《Steel in Translation》2010,40(12):1115-1118
Analysis of the magnetic properties of heat-treated steel yields a formula for the residual magnetization M
r of steel as the mean of its possible range. A reliable range of possible M
r variation is found for 08ю annealed steel. 相似文献
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The fatigue behavior of an Fe-0.30C-4.48Ni-l.32Al steel tempered to give three different microstructures of the same ultimate
tensile strength has been investigated by light and electron microscopy, low and high cycle fatigue tests, X-ray line broadening
and stress relaxation measurements. The three different heat treatments produced the following structures: I) a conventional
quenched and tempered microstructure with a high density of dislocations and elongated carbides, II) a microstructure of high
dislocation density, coarse carbides and fine coherent NiAl precipitates and III) a highly tempered micro-structure with a
recovered dislocation substructure, coarse carbides and fine coherent NiAl precipitates. In low cycle, strain controlled fatigue
cyclic softening in Treatment I was accompanied by a rearrangement of the dislocation substructure and a reduction in both
the internal stress and lattice microstrain. Treatment II, which remained cyclically stable during the initial portion of
the fatigue life, showed little change in the internal stress and dislocation density and showed a slight increase in lattice
microstrain. Treat-ment III, which initially cyclically hardened, exhibited a rise in internal stress, lattice microstrain
and dislocation density. The behavior of Treatments II and III is attributed in part to the presence of the fine NiAl precipitates
which appear to reduce the tendency of the transformation induced dislocation substructure to rearrange itself into a cell
structure during fatigue. In high cycle, stress controlled fatigue Treatment II showed the best fatigue resistance and Treatment
I the worst. Improvement in life was attributed to improved resistance to crack initiation.
Formerly Graduate Student, Marquette University, 相似文献
4.
The fatigue behavior of an Fe-0.3 wt pct C-4 wt pct Ni-1 wt pct Al-1 wt pct Cu precipitation hardening steel was investigated
in three different heat treated conditions which give similar tensile strengths but different microstructures. One heat treatment
produced a lightly tempered lath martensite having fine carbides and a high dislocation density. The other two heat treatments
produced highly tempered martensite with coarse carbides, fine intermetallic precipitates and a relatively low dislocation
density. The steel in the lightly tempered condition showed marked softening on strain cycling while the highly tempered conditions
resulted in both hardening and softening. The lightly tempered structure had better low cycle fatigue resistance but the two
highly tempered structures had better high cycle resistance. The dislocation substructure in the lightly tempered steel rearranges
itself and accommodates plastic strain during cyclic deformation while the substructure in the highly tempered structures
containing fine precipitates resists rearrangement. This difference is suggested as the reason for the differences in behavior.
The three conditions show little variation in their resistance to fatigue crack propagation. However, the highly tempered,
precipitate containing structures were much more resistant to fatigue crack initiation in notched specimens.
Former Postdoctoral Research Associate, Department of Materials Science and Engineering, and Walter P. Murphy Professor of
Materials Science and Engineering 相似文献
5.
Wayne M. Robertson Anthony W. Thompson 《Metallurgical and Materials Transactions A》1980,11(4):553-557
This work examined the role of microstructure in hydrogen permeation and trapping in a plain carbon steel. The experimental
material, SAE 1045 steel, was characterized both as to microstructure and as to permeation behavior; these data can be used
in interpreting hydrogen fracture observations. The gas-phase permeation results show that hydrogen is markedly trapped in
this steel, apparently at ferrite-carbide interfaces. This suggests that the trapped hydrogen could facilitate crack initiation
and crack propagation at these regions of high hydrogen concentration. The hydrogen traps are quite reversible, so that hydrogen
can be put in and taken out quite readily. The trapping energy ranged from 4.4 to 8.7 kcal/mol, with a mean value of 6.4 kcal/mol
(26.8 kj/mol), in agreement with previous studies. 相似文献
6.
Kao A.S. H. A. Kuhn O. Richmond W. A. Spitzig 《Metallurgical and Materials Transactions A》1989,20(9):1735-1741
Workability tests were performed on spheroidized {dy1045} steel to investigate the variation of forming limits due to the
suppression of void growth under superimposed hydrostatic pressure. Results showed that increasing pressure enhances formability,
as expressed by the increasing intercept and decreasing slope of the forming-limit line. A continuum mechanical model based
on the growth and coalescence of voids under externally applied pressure is proposed that ex-plains the experimental results. 相似文献
7.
The corrosion resistance of constructional carbon steel 20 and 45 with large-grain and ultrafinegrain structure is assessed in tests corresponding to State Standard GOST 9.308-85. Distinctive features are observed in the corrosion resistance of constructional carbon steel with ultrafine-grain structure. Stability groups of constructional carbon steel with different constructional types are identified. 相似文献
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《Acta Metallurgica Materialia》1994,42(1):99-104
A cloud of microcracks opens plastically around the tip of a long fatigue crack in sintered steel as it propagates. Because of the dilatation caused by the plastic opening of the microcracks, a negative stress intensity factor is induced at the crack tip which reduces the maximum crack tip stress intensity factor. At low values of the stress ratio the minimum crack tip stress intensity factor can be less than zero causing the crack to close and thus reducing the effective crack tip stress intensity factor range and retarding crack growth. Short cracks growing from pores do not have a systematic shield of microcracks and so propagate faster than long cracks at low stress ratios. 相似文献
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摘要:海洋工程用带肋钢筋要求有耐氯离子腐蚀能力,但选用双相不锈钢生产成本过高,不锈钢 碳钢轧制复合钢筋则可兼顾耐蚀性和低成本。覆层采用2205不锈钢,基材为低合金钢20MnSi,用有限元方法模拟钢筋的热轧复合过程,分析轧制过程尤其是成品孔中轧件的变形规律。有限元仿真发现,矩形组合坯料无孔型轧制时,其角部复合困难,而成品孔轧制时,钢筋横肋根部的应变最大,覆层在此位置减薄显著,应选择合适的复合坯覆层厚度。在实验室采用焊接、真空处理和热轧方法制备了直径为16mm的复合钢筋,屈服强度为485MPa,抗拉强度为701MPa,断后伸长率约为37.1%,复合界面剪切强度为317.5MPa。复合钢筋呈良好的冶金结合,Fe和Cr的扩散层厚度约为40μm。该工艺生产的复合带肋钢筋成本较不锈钢降低50%以上。 相似文献
12.
Cornelius Temmel Nils-Gunnar Ingesten Birger Karlsson 《Metallurgical and Materials Transactions A》2006,37(10):2995-3007
Anisotropy of forged steel components is especially adverse when it concerns rotationally symmetric components. Manganese
sulfides (MnS) in steels may be desired for their improvement of machining properties; however, they also deteriorate fatigue
behavior. A quantification of the effect of MnS on anisotropy is necessary to find an optimum for component dimensioning.
To isolate the influence of MnS on anisotropy only, high cleanness of the test material is required. The test material in
the current investigation was molten in a vacuum furnace to high-cleanness composition. Materials with two different S levels
were produced to detect variations in anisotropy according to amount, shape, and distribution of the MnS inclusions. The two
batches were cross-rolled to plates with a deformation ratio of 4.5. The MnS phase constitutes, upon forging or rolling, pancake-shaped
inclusions. In the case of cross-rolling, an in-plane rotational symmetry of the inclusions could be created. The shape and
size of these inclusions are essential for the mechanical behavior of the material. Push-pull fatigue testing was performed
in longitudinal (in plane) and short transversal directions relative to the rolling plane. The results showed strong anisotropy
of the fatigue behavior with inferior performance in short transverse directions where the principal stress is perpendicular
to the flattened inclusions. The anisotropy was somewhat more pronounced for the high-S material, resulting from a different
fatigue crack growth mechanism. 相似文献
13.
The fatigue behavior of an Fe-0.3 wt pet C-4 wt pet Ni-1 wt pet Al-1 wt pet Cu precipitation hardening steel was investigated in three different heat treated conditions which give similar tensile strengths but different microstructures. One heat treatment produced a lightly tempered lath martensite having fine carbides and a high dislocation density. The other two heat treatments produced highly tempered martensite with coarse carbides, fine intermetallic precipitates and a relatively low dislocation density. The steel in the lightly tempered condition showed marked softening on strain cycling while the highly tempered conditions resulted in both hardening and softening. The lightly tempered structure had better low cycle fatigue resistance but the two highly tempered structures had better high cycle resistance. The dislocation substructure in the lightly tempered steel rearranges itself and accommodates plastic strain during cyclic deformation while the substructure in the highly tempered structures containing fine precipitates resists rearrangement. This difference is suggested as the reason for the differences in behavior. The three conditions show little variation in their resistance to fatigue crack propagation. However, the highly tempered, precipitate containing structures were much more resistant to fatigue crack initiation in notched specimens. 相似文献
14.
《Acta Metallurgica Materialia》1993,41(7):2227-2233
The cyclic deformation behaviour of normalized SAE 1045 steel (german steel grade Ck 45) has been investigated over a range of temperatures between 20 and 375°C. Special attention has been paid to the effects of dynamic strain ageing, which are most pronounced around 300°C. Different types of deformation tests (tension tests, incremental step tests, and constant amplitude cyclic deformation tests under stress control with a stress amplitude of 400 MPa as well as under plastic strain control with a plastic strain amplitude of 0.5%) were carried out to observe the influence of temperature on the macroscopic mechanical behaviour. These tests were followed by TEM studies on microstructural features. In the temperature range of maximum dynamic strain ageing, the material was found to show maximum strength in unidirectional as well as in cyclic deformation tests. While the fatigue life is maximum at the temperature of maximum dynamic strain ageing in stress-controlled tests, it is minimum in plastic strain controlled tests. At the temperature of maximum dynamic strain ageing around 300°C, the dislocations are arranged in dense dislocation tangles and parallel dislocation walls, whereas at room and at higher temperatures (375°C) mainly dislocation cell structures are observed. 相似文献
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Translated from Poroshkovaya Metallurgiya, No. 7(355), pp. 40–44, July, 1992. 相似文献
18.
A study has been made of the fatigue of a V containing dual-phase steel, whose tensile strength is equivalent to that of SAE
980X high strength, low-alloy (HSLA) steels, as a function of prestrain. It is found that the cyclic stress-strain curve,
strain-life response and notch sensitivity are little affected by pre-strains of up to 8 pct: This is in contrast to monotonie
flow strength which increases substantially with prestrain. The fatigue performance of the dual-phase steel, while different
in detail from that of other HSLA steels, is intermediate between that for SAE 950X and 980X steels. However, the notch fatigue
behavior is equivalent to that of 980X steels. The fatigue response of dual-phase steel can be understood in terms of its
high rate of work hardening which is a consequence of its ferrite plus martensite microstructure. 相似文献
19.
The fatigue crack growth rates of two austenitic stainless steel alloys, AISI 301 and 302, were compared in air, argon, and hydrogen environments at atmospheric pressure and room temperature. Under the stresses at the crack tip the austenite in type 301 steel transformed martensitically to a’ to a greater extent than in type 302 steel. The steels were also tested in the cold worked condition under hydrogen or argon. Hydrogen was found to have a deleterious effect on both steels, but the effect was stronger in the unstable than in the stable alloy. Cold work decreased fatigue crack growth rates in argon and hydrogen, but the decrease was less marked in hydrogen than in argon. Metallographic, fractographic, and microhardness surveys in the vicinity of the fatigue crack were used to try to understand the reasons for the observed fatigue behavior. 相似文献
20.
L. F. Van Swam R. M. Pelloux N. J. Grant 《Metallurgical and Materials Transactions A》1975,6(1):45-54
The cyclic stress-strain curves, the low cycle and high cycle fatigue lives and the fatigue crack growth rates of annealed
(1 h 820°C) and aged (3 h 480°C) maraging steel 300 were determined. Incremental step testing and stable hysteresis loop tip
measurements were used to determine the cyclic σ-ε curves. Both annealed and aged maraging steels were found to cyclically soften at room temperature over a plastic strain
range from 0.1 to 20 pct. The S-N curves were determined from 10 to 107 cycles to failure by plastic strain controlled low cycle fatigue tests performed in air and load controlled high cycle fatigue
tests performed in dry argon. The test results compared very well with the theoretical lifetime predictions derived from Tomkins’
theory. Fatigue crack growth rates were measured in air and dry argon for the annealed and aged alloys. Crack growth rates
of annealed maraging steel were found to be equal to those of aged maraging steel at rates between 10-7 and 10-5 in./cycle. A significant difference in crack growth rates in the two environments was found at low stress intensity factor
ranges, indicating a high susceptibility to corrosion fatigue in the presence of water vapor. The mechanisms of cyclic softening
in the two alloys are discussed in terms of dislocations rearrangement in the annealed alloy and dislocation-precipitate interactions
in the aged alloy. 相似文献