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1.
Stress corrosion cracking of aluminum alloys 总被引:3,自引:0,他引:3
Markus O. Speidel 《Metallurgical and Materials Transactions A》1975,6(3):631-651
Stress corrosion cracking of aluminum alloys is reviewed. An extensive failure analysis shows how many service failures occurred
in the aerospace industry over a ten year period and what kind of alloys and stresses led to initiation and propagation of
stress corrosion cracks which caused these service failures. The paper contains most of the results of stress corrosion tests
with aluminum alloys that have been obtained to date with fracture mechanics techniques. Stress corrosion crack growth rate
measurements are compared with the results from smooth specimen testing and it is shown that the correlation between the different
test results is very satisfactory. The present and limited status of theoretical understanding of stress corrosion cracking
is outlined.
A major part of the paper is devoted to the results of the latest alloy development. High strength aluminum alloys of dramatically
increased stress corrosion resistance are available now. In the near future, stress corrosion resistant alloys of even higher
strength might become available. What is still lacking is a detailed understanding of the mechanisms by which stress corrosion
cracks initiate and propagate.
Brown Boveri Research Center, Baden, Switzerland
This paper is based on an invited presentation made at a symposium on “Advances in the Physical Metallurgy of Aluminum Alloys”
held at the Spring Meeting of TMS-IMD in Philadelphia, Pennsylvania, on May 29 to June 1, 1973. The symposium was co-sponsored
by the Physical Metallurgy Committee and the Non-Ferrous Metals Committee of TMS-IMD. 相似文献
2.
Al-Zn-Mg系铝合金应力腐蚀性能 总被引:4,自引:0,他引:4
研究了热处理制度和时效工艺的改变对Al-Zn-Mg系铝合金的组织结构、力学性能和应力腐 蚀性能的影响。研究结果表明:高温预析出可以改变Al-Zn-Mg系铝合金晶界的析出相大小和分 布,从而改善其抗应力腐蚀性能;在T6和T612种人工时效条件下,预析出的合金的抗应力腐蚀 性能均好于无预析出的合金。在自然时效状态下,引入超声波,对无预析出合金的应力腐蚀性能 进行了初步探索,发现超声波可以提高合金的抗应力腐蚀性能,而对合金的硬度无影响。 相似文献
3.
T. C. Tsai J. C. Chang T. H. Chuang 《Metallurgical and Materials Transactions A》1997,28(10):2113-2121
The effects of biaxial superplastic deformation and postforming heat treatment upon the stress corrosion cracking (SCC) of
a fine-grained 7475Al alloy plate have been investigated. For all postforming tempered conditions, increasing the extent of
superplastic deformation, which created more cavitations, would decrease the mechanical properties, the SCC resistance, and
the corrosion resistance. The influence of cavitation on the decay of elongation of the superplastically formed workpieces
is larger than that on the decay of its strength. Post-forming tempered by retrogression and reaging (RRA) treatment could
effectively improve the SCC resistance of workpieces in postforming T6 temper while not sacrificing the strength. However,
the benefit of improving the SCC resistance by means of the postforming RRA temper was decreased with increasing the extent
of superplastic deformation, because the SCC susceptibility increased as the extent of superplastic deformation increased
for each postforming tempered condition. The cavitation led to more anodic corrosion potential and pitting potential and to
an increase in both corrosion current density and passive current density, which would increase the SCC susceptibility. 相似文献
4.
Wu-Yang Chu Chi-Mei Hsiao Jun-Wen Wang 《Metallurgical and Materials Transactions A》1985,16(9):1663-1670
Stress corrosion cracking (SCC) of 7075 aluminum alloy in a 3.5 pet NaCl aqueous solution under compressive stress was investigated
using modified WOL notched specimen. The result showed that SCC could occur if an applied compressive displacement was larger
than a critical value. Finiteelement analysis indicated that there was a stress concentration and the stress components were
negative at the notch tip under the compressive displacement. Since the unloaded displacements were equal but opposite to
the loaded ones, no stress relaxation occurred throughout SCC. Thus, the SCC was induced by compressive stress. The threshold
stress intensity nucleating SCC from the notch under the compressive applied stress was 27.6 MPa m1/2, but the corresponding value under tensile stress was 8.3 MPa m1/2. Besides, the incubation period for SCC under compressive stress was one order of magnitude longer than that under tensile
stress in the sameK
1 The fracture surfaces of SCC under compressive stress were quite different from those under tensile stress. The latter was
composed of intergranular but the former was quasi-cleavage characterized by parallel striation pattern.
Formerly Student at Beijing University of Iron and Steel Technology 相似文献
5.
6.
R. F. Hehemann 《Metallurgical and Materials Transactions A》1985,16(11):1909-1923
The similarities and differences in the stress corrosion cracking response of ferritic and austenitic stainless steels in
chloride solutions will be examined. Both classes of materials exhibit a cracking potential: similar transient response (to
loading) of the potential in open circuit tests or the current in potentiostatic tests and similar enrichment of chromium
and depletion of iron in the film associated with localized corrosion processes. The ferritic steels are more resistant to
localized corrosion than are the austenitic steels, which is responsible for the difference in the influence of prior thermal
and mechanical history on cracking susceptibility of the two types of steel. Similarities in the fractography of stress corrosion
cracks and those produced by brittle delayed failure during cathodic charging of the ferritic steels indicate that hydrogen
embrittlement is involved in the failure process. 相似文献
7.
《Acta Metallurgica Materialia》1991,39(11):2597-2605
The stress corrosion cracking (SCC) susceptibility of two aluminum-lithium alloys, a binary AlLi and a ternary AlLiCu alloy, in 0.5 M NaCl solution was investigated using the constant elongation rate technique (CERT). Susceptibility increased with decreasing strain rate and with aging. The alloys were susceptible under both anodic and cathodic applied potentials. The susceptibility dependence of the alloys as a function of applied potential correlates well with published hydrogen permeability data. The susceptibility increased dramatically when hydrogen was charged into the specimen using a hydrogen re-combination “poison” during CERT testing. These experiments suggest that hydrogen plays a major role in the SCC of these alloys. A brittle hydride having the composition LiAlH4 forms in the AlLi system under conditions of severe SCC susceptibility. The brittleness of the hydride is explained. The formation of the hydride is a sufficient condition for SCC of AlLi alloys. A process of SCC in AlLi alloys is proposed wherein hydrogen causes damage by the formation of a hydride. 相似文献
8.
Stress corrosion cracking (SCC) ofβ
’-phase brasses in water at 20 °C was studied in four Cu-Zn binaries and one Cu-Zn-Sn ternary alloy using slow strain rate
tensile tests and load relaxation SCC of notched rods. Electron diffraction techniques were used to identify phases on the
fracture surfaces. All alloys were susceptible to SCC and it was found that decreasing the electron/atom(e/a) ratio of theβ
’-phase promoted transgranular SCC and increased the rate of cracking. The most rapid crack propagation rates were associated
with alloy compositions giving rise to a strain induced martensite transformation during SCC.
Formerly Graduate Student at the University of British Columbia 相似文献
9.
Stress corrosion cracking of an Al-Li alloy 总被引:1,自引:0,他引:1
Z. F. Wang Z. Y. Zhu Y. Zhang W. Ke 《Metallurgical and Materials Transactions A》1992,23(12):3337-3341
Stress corrosion cracking (SCC) has been studied in an Al-Li alloy with variables of orientation of specimen, heat treatment,
and applied potentials. The distribution of the electrochemical potential resulting from precipitate clusters was measured,
and the hydrogen content on the specimen surface was detected. The results showed that the SCC susceptibility under the peakaged
(PA) condition was higher than that under the natural (NA) and overaged (OA) conditions. The transverse (TL) specimen was
more susceptible to SCC propagation than the longitudinal (LT) specimen. The SCC susceptibility and the hydrogen content on
the specimen surface were dependent on the applied potentials. The hydrogen content increased when the applied potential changed
to positive or negative directions. There was a critical hydrogen content, below which local anodic dissolution (LAD) plays
an important role, above which hydrogen embrittlement (HE) plays an important role. 相似文献
10.
Wang Z. F. Zhu Z. Y. Zhang Y. Ke W. 《Metallurgical and Materials Transactions A》1992,23(1):3337-3341
Stress corrosion cracking (SCC) has been studied in an Al-Li alloy with variables of orientation of specimen, heat treatment, and applied potentials. The distribution of the electrochemical potential resulting from precipitate clusters was measured, and the hydrogen content on the specimen surface was detected. The results showed that the SCC susceptibility under the peak- aged (PA) condition was higher than that under the natural (NA) and overaged (OA) conditions. The transverse (TL) specimen was more susceptible to SCC propagation than the longitudinal (LT) specimen. The SCC susceptibility and the hydrogen content on the specimen surface were dependent on the applied potentials. The hydrogen content increased when the applied potential changed to positive or negative directions. There was a critical hydrogen content, below which local anodic dissolution (LAD) plays an important role, above which hydrogen embrittlement (HE) plays an important role. 相似文献
11.
R. S. Ondrejcin 《Metallurgical and Materials Transactions B》1970,1(11):3031-3036
Experimental studies show that hydrogen produced during the corrosion of titanium alloys by halide salts and subsequently absorbed by the titanium is responsible for cracking of these alloys. Autoradiography and proportional β counting were used to detect the diffusion of hydrogen into the metal matrix. Similar failure modes were observed in fractographic examinations of surfaces produced by hot-salt cracking and surfaces of precracked specimens pulled to failure in high pressure hydrogen gas. Stressed titanium-aluminum alloys cracked under low-energy proton bombardment and show that failure can be caused by the effects of stress and hydrogen alone. Similarities to hot-salt cracks were noted, and the approximate concentrations required to initiate and propagate cracks were calculated. 相似文献
12.
Initiation of stress corrosion cracks in aluminum alloys 总被引:3,自引:0,他引:3
Rajeshwar Singh Pathania Desmond Tromans 《Metallurgical and Materials Transactions A》1981,12(4):607-612
Studies on initiation of stress corrosion cracking (scc) were conducted on notched rods of aged Al-8.6Mg, Al-21.5Zn and Al-2.6Mg-6.3Zn
alloys tested in aqueous solutions and water-containing ethanol solutions under free corrosion conditions. It was found that
there is a definite scc initiation period (t) preceding crack propagation. The crack initiation rate (1/t) increased with
increasing initial stress intensity (KI,) at the notch. The crack initiation rates were thermally activated with apparent activation energies of Q ≈ 40 to 60 kJ/mol
in the ethanol based solutions and Q ≈ 109 kJ/mol in aqueous solutions. Cathodic hydrogen precharging prior to scc decreased
the subsequent crack initiation period. The results were discussed in relation to a hydrogen mechanism of scc and shown to
be entirely consistent with the lattice decohesion model developed by Oriani.
Formerly Graduate Student with the University of British Columbia 相似文献
13.
Xianzhong Guo Kewei Gao Lijie Qiao Wuyang Chu 《Metallurgical and Materials Transactions A》2001,32(6):1309-1312
Brass foil with a protective layer formed on one side was deflected during corrosion in an ammonia solution under various
applied potentials, and then corrosion-induced stress generated at brass/dezincification layer under different potentials
could be measured. At the same time, susceptibility to stress corrosion cracking (SCC) of brass in the ammonia solution under
various applied potentials was measured by using a single-edge notched specimen. At open-circuit potential, both corrosion-induced
tensile stress and susceptibility to SCC (I
σ) had a maximum value. Both tensile stress σ
p and susceptibility I
σ decreased slightly with decreasing potential under anodic polarization, but reduced steeply with a decrease in potential
under cathodic polarization. At the cathodic potential of − 500 mVSCE, corrosioninduced stress became compressive because of the copper-plating layer; correspondingly, susceptibility to SCC was
zero. Therefore, the variation of SCC susceptibility with potential is consistent with that of the corrosion-induced additive
stress. 相似文献
14.
The influence of different heat treatments upon the atmospheric stress corrosion cracking (SCC) of fine-grained 7475 Al-alloy
plates has been investigated. The small size of the matrix precipitates and grain-boundary precipitates (GBPs) was found to
be the main cause of atmospheric SCC suscepti-bility. Increasing the size of the matrix precipitates and GBPs by increasing
the degree of aging could improve the atmospheric SCC resistance. The size of the matrix precipitates was the major factor
affecting the atmospheric SCC resistance when GBPs were larger than a critical size that could nucleate hydrogen bubbles.
However, if the size of the GBPs was smaller than this critical size, the improvement of atmospheric SCC resistance due to
grain refinement, resulting from a more homo-geneous slip mode, could not be obtained because hydrogen embrittlement became
serious. By meas-uring the electrical conductivity, the influence of matrix precipitates, but not that of GBPs, on SCC susceptibility
could be obtained. Retrogression and reaging (RRA) treatment could effectively im-prove the atmospheric SCC resistance of
T6 temper because RRA temper could produce larger sizes of both the matrix precipitates and GBPs than could T6 tempered condition. 相似文献
15.
The susceptibility to stress-corrosion cracking (SCC) of rapidly solidified (RS) aluminum powder metallurgy (P/M) alloys 7090
and 7091, mechanically alloyed aluminum P/M alloy IN* 9052, and ingot metallurgy (I/M) alloys of similar compositions was
compared using bolt-loaded double cantilever beam specimens. In addition, the effects of aging, grain size, grain boundary
segregation, pre-exposure embrittlement, and loading mode on the SCC of 7091 were independently assessed. Finally, the data
generated were used to elucidate the mechanisms of SCC in the three P/M alloys. The IN 9052 had the lowest SCC susceptibility
of all alloys tested in the peak-strength condition, although no SCC was observed in the two RS alloys in the overaged condition.
The susceptibility of the RS alloys was greater in the underaged than the peak-aged temper. We detected no significant differences
in susceptibility of 7091 with grain sizes varying from 2 to 300 μm. Most of the crack advance during SCC of 7091 was by hydrogen
embrittlement (HE). Furthermore, both RS alloys were found to be susceptible to preexposure embrittlement—also indicative
of HE. The P/M alloys were less susceptible to SCC than the I/M alloys in all but one test. 相似文献
16.
The threshold stress intensity of stress corrosion cracking (SCC) in the NaCl solution, KISCC, has been measured for five low alloy steels. The effects of yield strength, alloy elements, microstructure and grain size on KISCC were studied. The results showed that KISCC decreased exponentially with increasing yield strength, σys, i.e., KISCC = 1.38 · 106exp(‐8.26 · 10‐3σys) for 40CrMoV steel and KISCC = 1.42 · 106exp(‐4.66 · 10‐3σys) for 30CrMnSiNi steel. For low‐alloy high‐strength steels with σys = 1400 MPa, the effect of alloy elements, microstructure and grain diameter larger than 7 μm on KISCC was little. The threshold stress intensity of hydrogen‐induced cracking during dynamical charging for 40CrMoTi steel decreased linearly with the logarithm of the concentration of diffusible hydrogen, C0, i.e., KIH = 31.3‐9.1lnC0. This equation was also applicable to SCC of a high‐strength steel in aqueous solution, and in this case, C0 is constant. The critical hydrogen enrichment concentration, Cth, necessary for SCC of high‐strength steel in water decreased exponentially with the increase in yield strength. It was possible to deduce the relationship between KISCC and σys, i.e., KISCC = Ak1exp(‐k2σys), where A = 3RT√πρ /2(1 + ν) , k1 and k2 are constants, which depend upon the compositions and microstructure of the steel as well as the test conditions. 相似文献
17.
Markus O. Speidel 《Metallurgical and Materials Transactions A》1981,12(5):779-789
The metallurgical influences on the stress corrosion resistance of many commercial stainless steels have been studied using
the fracture mechanics approach. The straight-chromium ferritic stainless steels, two-phase ferritic-austenitic stainless
steels and high-nickel solid solutions (like alloys 800 and 600) investigated are all fully resistant to stress corrosion
cracking at stress intensity (K1) levels ≤ MN • m-3/2 in 22 pct NaCl solutions at 105 °C. Martensitic stainless steels, austenitic stainless steels and precipitation hardened
superalloys, all with about 18 pct chromium, may be highly susceptible to stress corrosion cracking, depending on heat treatment
and other alloying elements. Molybdenum additions improve the stress corrosion cracking resistance of austenitic stainless
steels significantly. The fracture mechanics approach to stress corrosion testing of stainless steels yields results which
are consistent with both the service experience and the results from testing with smooth specimens. In particular, the well
known “Copson curve” is reproduced by plotting the stress corrosion threshold stress intensity (ATISCC) vs the nickel content of stainless steels with about 18 pct chromium.
Formerly with the BBC Brown Boveri Company, Baden, Switzerland 相似文献
18.
Sunggon Lim Sangshik Kim Chang-Gil Lee Sungjoon Kim 《Metallurgical and Materials Transactions A》2005,36(7):1977-1980
In the present study, the stress corrosion cracking (SCC) behavior of friction-stir-welded AI 6061-T651 alloy was examined
of −650 mV vs Ag/AgCl using a slow strain rate testing technique. The resistance to SCC was correlated to the percent change in tensile
elongation with exposure to 3.5 pct NaCl aqueous solution with respect to the reference environment. It was demonstrated the
the SCC resistance of friction-stir-welded Al 6061-T651 was considerably higher than that of parent material at an anodically
applied potential. In friction-stir-welded Al 6061-T651 alloy, the stress corrosion cracks occur only locally in the boundary
region between the dynamically recrystallized zone (DXZ) and the heat affected zone (HAZ) regions. However, the HAZ has much
lower strength properties compared with the rest of the material, and thus, fracture occurs there despite the increase in
stress intensity due to corrosion at the DXZ and HAZ boundary. Eventually, the tensile fracture in friction-stir-welded A1
6061-T651 was relatively unaffected by the SCCs formed in 3.5 pct NaCl aqueous solution. 相似文献
19.
A fracture mechanics study of stress corrosion cracking (scc) of cold worked AISI 310 austenitic steel, and an experimental
metastable austenite, was conducted in hot aqueous solutions of 44.7 wt pct MgCl2 and the results compared with previous studies on AISI 316 steel. Attention was directed towards Region II behavior where
crack propagation rate (v) was independent of stress intensity (KI). The apparent activation energy of Region II was found to be in the range ~65 to 75 kJ/mol, independent of the relative
proportions of intergranular and transgranular cracking. Also, electron diffraction studies of fracture surfaces showed that
α′-martensite formation was not a pre-requisite for scc, although it may influence crack propagation rates. Cracking was discussed
in terms of a hydrogen embrittlement model under hydrogen transport control in the austenite lattice. However, adsorption
(chemisorption) effects on repassivation and dissolution behavior could not be eliminated from consideration.
Alan J. Russell, Formerly Research Student, University of British Columbia. 相似文献
20.
通过SO2复合盐雾试验模拟工业污染海洋大气环境,结合有限元模拟分析、扫描电镜/能谱仪、光电子能谱分析等技术研究2024-T351铝合金在弹性应力区间的应力腐蚀开裂行为.结果表明:应力腐蚀开裂行为优先发生在2024-T351铝合金C型环的顶部应力集中区域;疏松的腐蚀产物层的形貌经历了由细棒状、团絮状到板块状的变化;试验6 h就可以监测到裂纹,进行到480 h的时候有贯穿裂纹形成,720 h的时候试样完全断裂;裂纹为穿晶和沿晶混合机制,主裂纹以穿晶机制沿C型环法线扩展,二次裂纹沿晶界扩展. 相似文献