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1.
A new Al-Li alloy containing 2.3 wt pct Li, 6.5 wt pct Mn, and 0.65 wt pet Zr, for high-temperature applications, has been
processed by a rapid solidification (RS) technique (as powders by inert gas atomization) and then thermomechanically treated
by hot isostatic pressing (hipping) and hot extrusion. As-received and thermomechanically treated powders (of various size
fractions) were characterized by X-ray diffraction and scanning and transmission electron microscopy (SEM and TEM, respectively).
Phase analyses in the as-processed materials revealed the presence of two Mn phases (Al4Mn and Al6Mn), one Zr phase (Al3Zr), two Li phases (the stable AlLi and the metastable Al3Li), and the αAl solid solution with high excess in Mn solubility (up to close the nominal composition in the as-atomized
powders). Extruded pieces were solutionized at 370 °C and 530 °C for various soaking times (2 to 24 hours). A variety of aging
treatments was practiced to check for the optimal (for tensile properties) aging procedure, which was found to be the following:
solutioning at 370 °C for 2 hours and water quenching + 1 pct mechanical stretching + one step aging at 120 °C for 3 hours.
The mechanical properties, at room and elevated temperatures, of the “hipped” and hot extruded powders are compared following
the optimal solutioning and aging treatments. The results indicate that Mn is indeed a favorable alloying element for rapidly
solidified Al-Li alloys to retain about 85 to 95 pct of the room-temperature tensile properties even at 250 °C, though room-temperature
strength is not satisfactory in itself. However, specific moduli are by 20 to 25 pet higher than those of the 2024 series
duralumin-type alloys. Ductilities at room temperatures are in the low 1 to 2.5 pct range and show no improvement over other
Al-Li alloys. 相似文献
2.
L. del Castillo H. M. Hu E. J. Lavernia Y. Wu 《Metallurgical and Materials Transactions A》1999,30(5):1381-1389
High-Li alloys, with the composition Al-3.8Li-XCu-1.0Mg-0.4Ge-0.2Zr, were synthesized using a spray deposition technique (wt. pct, X=0∼1.5). The microstructure of the spray-deposited Al-Li alloys consisted of equiaxed grains with an average grain size in
the range from 20 to 50 μm. The grain-boundary phases were fine and discrete. The spray-deposited and thermomechanically processed materials were isothermally
heat treated at 150 °C and 170 °C to investigate the age-hardening kinetics. It was noted that the spray-deposited Al-3.8Li-XCu-1.0Mg-0.4Ge-0.2Zr alloys exhibited relatively sluggish aging behavior. The peak-aged condition was achieved at 170 °C in
the range from 20 to 90 hours. It was noted that Cu increases the hardness of alloys during aging. Moreover, the influence
of Cu on age-hardening kinetics is marginal. The mechanical properties of the spray-deposited and extruded Al-Li alloys were
studied in the underaged, peak-aged, and overaged conditions. For example, the peak-aged yield strength, tensile strength,
and ductility of Al-3.8Li-1.0Cu-1.0Mg-0.4Ge-0.2Zr are 455 MPa, 601 MPa, and 3.1 pct, respectively. Moreover, an increase in
the Cu content of the alloy led to improvements in strength, with only slight changes in ductility, for Cu contents up to
1.0 wt pct. Beyond this range, an increase in Cu content led to decreases in both strength and ductility. 相似文献
3.
The rapidly-quenched structures of liquid Al-Mn-Zr ternary alloys and Al-Mn binary alloys and their decomposition behaviors
were investigated by hardness tests, X-ray diffraction analyses, and TEM observations. The solid solubility of Mn can be extended
to about 10 wt pct irrespective of whether the alloys contain 1 wt pct Zr or not. The solidification structures are composed
of fine dendritic cells and with increasing Mn content, interdendritic precipitates gather volume and branch out into the
cell grains. The decomposition of rapidly-quenched alloys takes place during aging for 1 hour at temperatures of 300 to 350
°C, and the dependence of the decomposition temperatures on the Mn content varies in this range. Precipitation hardening of
the ternary alloys is intensified by the addition of Mn up to about 7 wt pct and proceeds in a two-step manner during aging
in the temperature range examined (350 to 450 °C). It is suggested that the precipitates contributing to the maximum hardening
are pseudomorphous to the Al6Mn equilibrium phase. 相似文献
4.
Joonyeon Chang Inge Moon Chongsool Choi 《Metallurgical and Materials Transactions A》1998,29(7):1873-1882
Analytical transmission electron microscopy and thermal analysis of as-extruded Al-4.7 pct Zn-2.5 pct Mg-0.2 pct Zr-X wt pct Mn alloys, with Mn contents ranging from 0.5 to 2.5 wt pct, were carried out to elucidate the microstructural change
and accompanying mechanical properties during subsequent heat treatments. The as-extruded alloy was fabricated from rapidly
solidified powder and consisted of a fine, metastable manganese dispersoid and the ternary eutectic T phase (Al2Mg3Zn3). Solution heat treatment resulted in the formation of the stable Al6Mn phase and complete dissolution of the T phase. Formation of stable Al6Mn was made by two routes: by phase transition from metastable Mn dispersoids which already existed, and from the supersaturated
solid solution by homogeneous nucleation. The density of the Al6Mn phase increased with the addition of manganese, while the shape and average size remained unchanged. A significant increase
in the hardness was observed to coincide with the formation of the Al6Mn phase. Similarly, the tensile strength increased further after the aging treatment, and the increment was constant over
the content of Mn in the alloy, which was explained by the contribution from the same amount of precipitates, MgZn2. Results of thermal analysis indicated that the dissolution of the T phase started near 180 °C and that formation of Al6Mn occurred at about 400 °C, suggesting that further enhancement of strength is possible with the modification of the heat-treatment
schedule. 相似文献
5.
Influence of Extrusion on the Microstructure and Mechanical Behavior of Mg-9Li-3Al-xSr Alloys 总被引:1,自引:0,他引:1
Yan Yang Xiaodong Peng Haiming Wen Baolong Zheng Yizhang Zhou Weidong Xie Enrique J. Lavernia 《Metallurgical and Materials Transactions A》2013,44(2):1101-1113
Mg-9Li-3Al-xSr (LA93-xSr, x = 0, 1.5, 2.5, and 3.5 wt pct) alloys were cast and extruded at 533 K (260 °C) with an extrusion ratio of 28. The microstructure and mechanical response are reported and discussed paying particular attention to the influence of extrusion and Sr content on phase composition, strength, and ductility. The results of the current study show that LA93-xSr alloys contain both α-Mg (hcp) and β-Li (bcc) matrix phases. Moreover, the addition of Sr refines the grain size in the as-cast alloys and leads to the formation of the intermetallic compound (Al4Sr). Our results show significant grain refinement during extrusion and almost no influence of Sr content on the grain size of the extruded alloys. The microstructure evolution during extrusion is governed by continuous dynamic recrystallization (CDRX) in the α-Mg phase, whereas discontinuous dynamic recrystallization (DDRX) occurs in the β-Li phase. The mechanical behavior of the extruded LA93-xSr alloy is discussed in terms of grain refinement and dislocation strengthening. The tensile strength of the extruded alloys first increases and then decreases, whereas the elongation decreases monotonically with increasing Sr; in contrast, hardness increases for all Sr compositions studied herein. Specifically, when Sr content is 2.5 wt pct, the extruded Mg-9Li-3Al-2.5Sr (LAJ932) alloy exhibits a favorable combination of strength and ductility with an ultimate tensile strength of 235 MPa, yield strength of 221 MPa, and an elongation of 19.4 pct. 相似文献
6.
Although Al-Li-Cu alloys showed initial promise as lightweight structural materials, implementation into primary aerospace
applications has been hindered due in part to their characteristic anisotropic mechanical and fracture behaviors. The Air
Force recently developed two isotropic Al-Li-Cu-X alloys with 2.1 wt pct Li and 1.8 wt pct Li designated AF/C-489 and AF/C-458,
respectively. The elongation at peak strength was less than the required 5 pct for the 2.1 wt pct Li variant but greater than
10 pct for the 1.8 wt pct Li alloy. The objectives of our investigations were to first identify the mechanisms for the large
difference in ductility between the AF/C-489 and AF/C-458 alloys and then to develop an aging schedule to optimize the microstructure
for high ductility and strength levels. Duplex and triple aging practices were designed to minimize grain boundary precipitation
while encouraging matrix precipitation of the T1 (Al2CuLi) strengthening phase. Certain duplex aged conditions for the AF/C-489 alloy showed significant increases in ductility
by as much as 85 pct with a small decrease of only 6.5 and 2.5 pct in yield and ultimate tensile strength, respectively. However,
no significant variations were found through either duplex or triple aging practices for the AF/C-458 alloys, thus, indicating
a very large processing window. Grain size and δ′ (Al3Li) volume fraction were determined to be the major cause for the differences in the mechanical properties of the two alloys. 相似文献
7.
The present study was undertaken to investigate the effect of solution treatment (in the temperature range 520 °C to 550 °C)
and artificial aging (in the temperature range 140 °C to 180 °C) on the variation in the microstructure, tensile properties,
and fracture mechanisms of Al-10 wt pct Si-0.6 wt pct Mg/SiC/10p composite castings. In the as-cast condition, the SiC particles are observed to act as nucleation sites for the eutectic
Si particles. Increasing the solution temperature results in faster homogenization of the microstructure. Effect of solution
temperature on tensile properties is evident only during the first 4 hours, after which hardly any difference is observed
on increasing the solution temperature from 520 °C to 550 °C. The tensile properties vary significantly with aging time and
temperature, with typical yield strength (YS), ultimate tensile strength (UTS), and percent elongation (EL) values of ∼300
MPa, ∼330 MPa, and ∼1.4 pct in the underaged condition, ∼330 MPa, ∼360 MPa, and ∼0.65 pct in the peakaged condition, and ∼323
MPa, ∼330 MPa, and ∼0.8 pct in the overaged condition. Prolonged solution treatment at 550 °C for 24 hours results in a slight
improvement in the ductility of the aged test bars. The fracture surfaces exhibit a dimple morphology and cleavage of the
SiC particles, the extent of SiC cracking increasing with increasing tensile strength and reaching a maximum in the overaged
condition. Microvoids act as nucleation sites for the formation of secondary cracks that promote severe cracking of the SiC
particles. A detailed discussion of the fracture mechanism is given. 相似文献
8.
Jin-feng Li Long Xu Chao Cai Yong-lai Chen Xu-hu Zhang Zi-qiao Zheng 《Metallurgical and Materials Transactions A》2014,45(12):5736-5748
The influence of 0.72 pct Zn addition on the tensile properties of Al-2.7Cu-1.7Li-0.3Mg alloys was investigated. Their intergranular corrosion (IGC) dependence on aging [T6 type at 423 K (150 °C) and 448 K (175 °C) and T8 type at 423 K (150 °C)] time was studied. An IGC diagram associated with aging process was established. The addition of 0.72 pct Zn enhanced the strength of the Al-Li alloy with T6 type aging at 448 K (175 °C). With aging process, the corrosion mode of the T6-aged Al-Li alloys was changed in the following order: pitting and local IGC (initial aging stage), general IGC (underaging stage), local IGC (near peak-aging stage), and pitting (overaging stage) again. The IGC depth was increased first and then decreased with aging time extension. The corrosion potential change of grains and the microstructure variation were used to explain the IGC sensitivity of the Al-Li alloy with different tempers. Meanwhile, 0.72 pct Zn addition decreased the IGC sensitivity of the Al-Li alloy, especially the T6-aged Al-Li alloy. 相似文献
9.
Structure and properties of a β solution treated,quenched, and aged si-bearing near-α titanium alloy
The microstructure, tensile properties, and fractographic features of a near-α titanium alloy, IMI 829(Ti-6.1 wt pct Al-3.2
wt pct Zr-3.3 wt pct Sn-1 wt pct Nb-05 wt pct Mo-0.32 wt pct Si) have been studied after aging over a temperature range of
550°C to 950°C for 24 hours following solution treatment in the β phase field at 1050°C and water quenching. Transmission
electron microscopy studies revealed that aging at 625°C and above produced discrete silicides at α′ interplatelet boundaries.
However, aging at 900°C and above has also resulted in the precipitation of β phase along the lath boundaries of martensite.
The silicides have been found to have a hexagonal structure withc=0.36 nm anda=0.70 nm (designated as S2 by earlier workers). There is a significant improvement in yield and ultimate tensile strength after aging at 625°C, but
there is less improvement at higher aging temperatures. The tensile ductility is found to be drastically reduced. While the
fracture surface of the unaged specimen shows elongated dimples, the aged samples show a mixed mode of fracture, consisting
of facets, featureless parallel bands, and extremely fine dimples. 相似文献
10.
T. G. Nieh A. R. Pelton W. C. Oliver J. Wadsworth 《Metallurgical and Materials Transactions A》1988,19(5):1173-1178
A rapidly solidified Al-10 wt pct Be-3 wt pet Li alloy has been produced by a melt-spinning technique. The aging behavior
of the melt-spun ribbon has been characterized by a number of techniques, including differential scanning calorimetry, hardness
measurements, and transmission electron microscopy. The results have shown that the aging responses of the ternary Al-Be-Li
alloy are very similar to those of Al-Li binary alloys. Specifically, δ′ precipitates are formed at temperatures near 180
°C and they transform to δ at temperatures around 300 °C. Microstructural examination indicates that, in the Al-Be-Li alloy,
α-Be particles are present in the matrix as independent dispersoids and, apparently, have little effect on the aging behavior
of the Al-Li matrix; no new phases are present in the matrix of specimens heat treated up to 400 °C. The α-Be particles coarsen,
however, above a temperature of approximately 300 °C. The growth of α-Be particles follows the classical Ostwald coarsening
type of mechanism. 相似文献
11.
Precipitation in rapidly solidified Al-Mn alloys 总被引:1,自引:0,他引:1
D. Shechtman R. J. Schaefer F. S. Biancaniello 《Metallurgical and Materials Transactions A》1984,15(11):1987-1997
Precipitation at 450 °C was studied in melt-spun ribbons containing up to 15 wt pct Mn in solid solution in Al. The as-spun
ribbons were microsegregation-free at compositions up to 5 wt pct Mn, but in more concentrated alloys a cellular microstructure
was present. Upon annealing, four precipitate phases are observed, some of them being found preferentially on cell boundaries
and others being found within the cells. Al6Mn, G, and the Gℍ phase can coexist for long times at 450 °C, but the G phase appears to be slightly more stable. A less stable
T phase was detected in Al-5 wt pct Mn foils following short annealing periods. The supersaturation of the Al matrix can persist
for many hours in alloys containing up to 3 wt pct Mn, but is essentially gone after 1 hour in alloys with 5 wt pct Mn or
more.
On leave at the Center for Materials Research, The Johns Hopkins University, Baltimore, MD 21218. R.J. 相似文献
12.
K. Yu. Chervyakova N. A. Belov M. E. Samoshina A. A. Yakovlev 《Russian Journal of Non-Ferrous Metals》2018,59(4):412-418
Aluminum alloys of the Al–Cu–Mn (Zr) system possess high strength and manufacturability without heat treatment (HT). In order to investigate the possibility of fabricating an aluminum boron-containing alloy in the form of sheet rolling with increased strength without the HT, Al–2% Cu–1.5% Mn–2% B and Al–2% Cu–1.5% Mn–0.4% Zr–2% B alloys are prepared. To exclude the deposition of refractory boride particles, smelting is performed in a RELTEK induction furnace providing intense melt stirring. The smelting temperature is 950–1000°C. Pouring is performed into 40 × 120 × 200 mm graphite molds. It is established using computational methods (Thermo-Calc) that manganese forms complex borides with aluminum and zirconium at the smelting temperature and a sufficient amount of manganese remains in liquid, while zirconium is almost absent in it. The formation of AlB2Mn2 complex boride is proved experimentally (scanning electron microscopy and micro X-ray spectral analysis), but the amount of manganese remaining in the solid solution is sufficient to form particles of the Al20Cu2Mn3 phase in an amount reaching 7 wt %. Boron in the zirconium-containing alloy stimulates the isolation of primary crystals Al3Zr, in connection with which an insufficient amount of zirconium remains in the aluminum solid solution for strengthening. The possibility of fabricating thin-sheet rolling smaller than 0.3 mm in thickness with uniformly distributed agglomerations of the boride phase with a particle size smaller than 10 µm is shown. A high level of strength (up to 543 MPa) is attained with no use of quenching or aging due to the isolation of dispersoids of the Al20Cu2Mn3 phase during hot deformation (t = 450°C). 相似文献
13.
Aluminum-manganese alloys with compositions ranging between 0 and 27 wt pct Mn were electrodeposited at 150°C onto copper
substrates from a chloroaluminate molten salt electrolyte with a controlled addition of MnCl2. The specimens were studied by scanning electron microscopy (SEM), transmission electron microscopy (TEM), energy dispersive
spectroscopy (EDS), and X-ray diffraction. The addition of small amounts of Mn results in the formation of a supersaturated
fcc solid solution of Mn in Al. At the higher Mn content, an amorphous phase is established. The highly faceted crystalline
surface of pure Al and Al−Mn solid solution becomes smooth and nearly specular when the amorphous phase is present. The amorphous
phase appears in the form of rounded grains and has a lower limit of Mn concentration close to the Al6Mn composition. There is a concentration discontinuity between the above limit and the higher Mn concentration limit of the
fcc phase (about 9 wt pct). Appearance of the amorphous phase in the alloy results in a decrease in the Mn concentration in
solid solution to about 2 wt pct. Crystallization of the amorphous phase starts at the fcc-amorphous phase interface at 230°C.
As a result of treatment at 230 °C to 340 °C, the amorphous phase completely transforms into Al6Mn, while the fcc phase is unaffected. Prior to crystallization, the amorphous phase shows a modification that could be interpreted
as the formation of a fine-grained icosahedral phase. The formation and distribution of phases by electrodeposition and rapid
solidification are discussed. 相似文献
14.
Effect of processing and heat treatment on behavior of Cu-Cr-Zr alloys to railway contact wire 总被引:3,自引:0,他引:3
Qiang Liu Xiang Zhang Yan Ge Jing Wang Jian-Zhong Cui 《Metallurgical and Materials Transactions A》2006,37(11):3233-3238
A new series of Cu-Cr-Zr alloys to be used as railway contact wire, Cu-0.26 wt pct Cr-0.15 wt pct Zr, Cu-0.13 wt pct Cr-0.41
wt pct Zr, and Cu-0.34 wt pct Cr-0.41 wt pct Zr, were studied. The results indicated that processing and aging treatment had
an effect on the microstructure, tensile strength, and electrical conductivity behavior of the Cu-Cr-Zr alloys. Process I
(solution treatment + cold work + aging) was superior to process II (cold work + solution treatment + aging), because precipitation
can occur heterogeneously at the dislocations and subcells. An appropriate processing and aging treatment may improve the
properties of the alloys due to the formation of fine, dispersive, and coherent precipitates within the matrix. It is demonstrated
that the best combination of tensile strength and electrical conducitivity, on the order of 599 MPa and 82 pct IACS (International
Annealed Copper Standard), respectively, can be obtained in alloy Cu-0.34 wt pct Cr-0.41 wt pct Zr in the solution-heat-treated,
cold-worked, and aged condition. The mechanism of tensile and conductive properties of Cu-Cr-Zr alloy is also discussed. 相似文献
15.
Al–Cu–Mn (Zr) aluminum alloys possess high strength and manufacturability without operations of thermal treatment (TT). In order to investigate the fabrication possibility of the aluminum boron-containing alloy in the form of sheet rolling with an increased strength without TT, Al–2% Cu–1.5% Mn–2% B and Al–2% Cu–1.5% Mn–0.4% Zr–2% B alloys are prepared. To exclude the precipitation of refractory boride particles, smelting is performed in a RELTEK induction furnace providing intense melt stirring. The smelting temperature is 950–1000°C. Pouring is performed into graphite molds 40 × 120 × 200 mm in size. It is established using computational methods (Thermo-Calc) that manganese forms complex borides with aluminum and zirconium at the smelting temperature; herewith, a sufficient amount of manganese remains in liquid, while zirconium is almost absent. The formation of AlB2Mn2 complex boride is proven; however, the amount of manganese remaining in the solid solution is sufficient to form the particles of the Al20Cu2Mn3 phase in amounts of up to 7 wt %. Boron stimulates the isolation of Al3Zr primary crystals in the alloy with zirconium; in connection with this, an amount of zirconium insufficient for hardening remains in the aluminum solid solution. The possibility of fabricating thin-sheet rolling with a thickness smaller than 0.3 mm with homogeneously distributed accumulations of the boride phase with a particle size smaller than 10 μm is shown. A high strength level (up to 543 MPa) is attained without using quenching and aging due to the precipitation of dispersoids of the Al20Cu2Mn3 phase during hot deformation (t = 450°C). 相似文献
16.
Ilana Timokhina Hossein Beladi Xiang-Yuan Xiong Peter D. Hodgson 《Metallurgical and Materials Transactions A》2013,44(11):5177-5191
The aging behavior of a thermomechanically processed Mo-Al-Nb transformation-induced plasticity steel with ultrafine microstructure was investigated using transmission electron microscopy and atom probe tomography (APT). Strain aging at 73 K (200 °C) for 1800 seconds led to a significant bake-hardening response (up to 222 MPa). Moreover, aging for 1800 seconds at room temperature after 4 pct pre-strain also revealed a bake-hardening response (~60 MPa). The experimental results showed the formation of carbon Cottrell atmospheres around dislocations and the formation of carbon clusters/fine carbides in the bainitic ferrite during aging. It is proposed that this is associated with the high dislocation density of bainitic ferrite with formation of a complex dislocation substructure after pre-straining and its high average carbon content (~0.35 at. pct). The segregation of carbon and substitutional elements such as Mn and Mo to the retained austenite/bainitic ferrite interface during aging was observed by APT. This segregation is likely to be the preliminary stage for Mo-C particles’ formation. The aging after pre-straining also induced the decomposition of retained austenite with formation of ferrite and carbides. 相似文献
17.
Proloy Nandi Satyam Suwas Subodh Kumar Kamanio Chattopadhyay 《Metallurgical and Materials Transactions A》2013,44(6):2591-2603
Aluminum scandium binary alloys represent a promising precipitation-hardening alloy system. However, the hardness of the binary alloys decreases with the rapid coarsening of Al3Sc precipitate during high-temperature aging. In the current study, we report a new approach to compensate for the loss of mechanical properties by combining rapid solidification with very small ternary addition of transition metal Ni. This addition yields dispersion, and at a critical concentration improves the mechanical properties. We explore additions of a maximum of 0.06 at. pct of Nickel to a binary Al-0.14 at. pct Sc alloy, which yield nickel-rich dispersions. We report two kinds of biphasic dispersions containing AlNi2Sc/Al9Ni2 and α-Al/Al9Ni2 phase combinations. The maximum improvement in mechanical properties occurs with the addition of 0.045 at. pct Ni with a yield strength of 239 ± 7 MPa for an aging treatment at 583 K (310 °C) for 15 hours. 相似文献
18.
An alloy containing 80.0 pct Ni, 12.65 pct Fe, 6.74 pct Mo, 0.36 pct Zr, and 0.25 pct Mn by weight was cast, homogenized,
and successively cold rolled into thin strips with area reductions of 0, 50, 75, and 90 pct. Annealed samples were studied
by optical and electron microscopy, electron diffraction, and magnetic testing to determine the effects of cold work and annealing
upon the microstructure and magnetic properties of the alloy. Cold work produced a high initial hardness together with high
coercive force. Recrystallization of the cold worked structures occurred upon annealing at 600°C (873 K) and above and caused
significant and parallel decreases in hardness and coercive force. The activation energy for recrystallization was found to
be 80.5 kcal/g mole (337.0 kJ/g mole) for the 50, 75, and 90 pct cold worked specimens. After annealing at 600°C (873 K),
a small number of spherical Ni4Mo particles were observed, but the particles produced little change in magnetic properties apparently because of their relatively
coarse size and large spacing. Beginning at 700°C (973 K) ribbon-shaped particles of a Ni5Zr intermetallic compound also precipitated out of solid solution. Both the Ni4Mo and Ni5Zr precipitates were the result of a homogeneous continuous precipitation reaction within the grains. A peak in coercive force
at 800°C (1073 K) is attributed to domain wall pinning associated with the fine distribution of rodlike Ni5Zr particles. Cold working 90 pct and aging at 800°C (1073 K) was found to increase coercive force by almost 60 pct from the
minimum produced by complete recrystallization. Annealing, however, decreased hysteresis and improved squareness. 相似文献
19.
Chuan-Ming Tseng Wen-Ta Tsai Horng-Yih Liou 《Metallurgical and Materials Transactions A》2003,34(1):95-103
The effect of nitrogen content on the stress corrosion cracking (SCC) behavior of 22 pct Cr duplex stainless steel (DSS) in
chloride solutions was investigated in this study. Slow strain rate testing (SSRT) was employed to evaluate the SCC susceptibility.
The experimental results showed that the tensile strength and ductility of 22 pct Cr DSS increased with increasing amount
of nitrogen (in the range of 0.103 to 0.195 wt pct). Slow strain rate testing results indicated that 22 pct Cr DSSs were resistant
to SCC in 3.5 wt pct NaCl solution at 80 °C. However, environmentally assisted cracking occurred in 40 wt pct CaCl2 solution at 100 °C and in boiling 45 wt pct MgCl2 solution at 155 °C, respectively. The effects of environment and nitrogen content in DSS on the cracking susceptibility are
discussed in this article. Selective dissolution of ferrite phase was found to participate in the SCC process for tests in
CaCl2 solution. At temperatures above 80 °C, dynamic strain aging was found to occur in various environments at a strain beyond
plastic deformation. 相似文献
20.
Interrupted hot torsion tests at 450 °C have been performed on homogenized as-cast specimens of Al-Mg alloys. The chemical
compositions are approximately Al-4.85 pct Mg-0.74 pct Mn-0.22 pct Cr. The testpieces have been homogenized by three different
heating schedules, and the number of revolutions to fracture in hot torsion tests has been measured. The tests lead to the
finding that minor Si impurity, as little as 0.05 pct, is very harmful to the hot ductility. On the other hand, Fe impurity
up to 0.34 pct has no influence. It is also found that homogenization schedule is very important to hot ductility. A two-stage
heating consisting of a preheating at 430 °C for one and a half hours plus a soaking at 530 °C for eight hours results in
the best hot ductility. Three different kinds of interdendritic precipitates of the compositions (Fe, Mn)Alx, (Cr, Mn, Fe, Ti)Al7, and Mg2Si have been identified by electron microscopy. After homogenization submicron dispersoids of the composition MnAl6, containing Fe and Cr as alloying elements, precipitate within the dendrites. These dispersoids are shown to exert major
influences on hot ductility.
Formerly Head of Materials Research with Materials Research Laboratories, Industrial Technology Research Institute. 相似文献