共查询到20条相似文献,搜索用时 15 毫秒
1.
We report in this paper a study of surface segregation in austenitic stainless steel. Auger electron spectroscopy was used
to measure segregation as a function of time and temperature. We have found that P, N, S, Cr, and Ni will all segregate to
the surface. However, their presence on the surface often depends on the competitive and attractive interactions between the
various elements. We show that thermodynamic data on ternary liquid iron alloys are quite valuable in predicting these interactions.
We also discuss possible applications of these studies. 相似文献
2.
Brager H. R. Straalsund J. L. Holmes J. J. Bates J. F. 《Metallurgical and Materials Transactions B》1971,2(7):1893-1904
Metallurgical and Materials Transactions B - The microstructure of annealed AISI Type 304 and type 316 stainless steels has been characterized by transmission electron microscopy as a function of... 相似文献
3.
The nonmetallic phase in 08X18H10T and 03X18H10 vacuum-treated austenitic stainless steel is investigated by means of a scanning electron microscope. The composition of the nonmetallic inclusions in cast samples of metal from the casting ladle, the vacuum unit, and the continuous-casting machine and samples of cold-rolled sheet (thickness 1.2 mm) is studied. In 08X18H10T steel samples from the tundish of the continuous-casting machine, the nonmetallic phase consists mainly of titanium-nitride aggregations, the crystals of which contain oxides of aluminum and titanium; a few of the nonmetallic inclusions are small globules with a titanium-oxide shell. In cold-rolled sheet, the nonmetallic inclusions are distributed over the whole cross section and consist of small (5–6 μm) crystals of titanium nitrides. Cast samples of 03X18H10 austenitic titanium-free steel are relatively free of nonmetallic inclusions. The nonmetallic phase consists mainly of small inclusions of alumocalcium silicate. In cold-rolled sheet (thickness 1.2 mm), the nonmetallic phase consists of a few very small globules (2–3 μm). The results are compared with the composition of the nonmetallic phase in analogous steel with no vacuum treatment. 相似文献
4.
5.
Hydrogen attack in an austenitic stainless steel 总被引:1,自引:0,他引:1
M. J. Yacamán T. A. Parthasarathy J. P. Hirth 《Metallurgical and Materials Transactions A》1984,15(7):1485-1490
A titanium stabilized 321 grade austenitic stainless steel was exposed to hydrogen at 14 MPa pressure and at 873 K. Hydrogen
attack occurred in the form of small bubbles at alloy-carbide-matrix interfaces. The damaged regions were studied by transmission
electron microscopy, and the gas composition in the bubbles was analyzed. The results are discussed in terms of a thermodynamic
analysis of possible hydrogen attack reactions. 相似文献
6.
日益增长的工业需求推动着超级奥氏体不锈钢的研发,以研发时间为序阐述超级奥氏体不锈钢3个发展阶段。第1个阶段主要是为解决硫酸介质环境的耐腐蚀性而开发的不锈钢;第2个阶段是在第1阶段研发钢的基础上添加质量分数约为0.2%的N元素、并将Mo元素质量分数增加到约6%而研发的几种耐腐蚀性能良好的超级奥氏体不锈钢;第3个阶段是在6%Mo钢的基础上将Cr、Mo、N含量都进行较大幅度的提高,其中Mo元素质量分数增加到约7%,N元素质量分数控制在0.5%左右,并加入适量Mn元素而研发出耐腐蚀性优异的超级奥氏体不锈钢。阐述了超级奥氏体不锈钢研发过程中的2个重要技术,即炉外精炼与氮合金化技术,并展望了超级奥氏体不锈钢的未来发展及推广应用。 相似文献
7.
8.
The macro-and microstructures of about fifty different stainless welds of the AISI/ AWS 300 series are analyzed. The results
indicate that under conditions corresponding to a typical shielded metal arc (SMA) welding the welds with a ratio in the range
1.48≾Cr
eq
/Ni
eq
≾1.95, where Ni
eq
and Cr
eq
are the nickel and chromium equivalents on the Schaeffler diagram, solidify in accordance with a duplex mode with the delta
ferrite as the primary (leading) phase. The austenite forms between ferrite dendrites through a three-phase reaction between
liquid, ferrite and austenite, and subsequently grows into the ferrite by either an equiaxial or an acicular mechanism, resulting
in a drastic decrease in the volume fraction of the delta ferrite. The micro-structure at room temperature is characterized
by a general irregularity and the varied morphology of the ferrite. The compositional differences observed at room temperature
are a consequence both of the solidification and the solid state transformation.
Formerly Research Staff Member, Laboratory of Physical Metallurgy, University of Oulu. 相似文献
9.
In situ measurements are reported of electrical resistance changes in 316 austenitic stainless steel after abruptly raising or lowering
temperature in the range from 440 °C to 550 °C subsequent to equilibration. These changes are found to be reproducible and
have a magnitude roughly proportional to the temperature change. They are believed to be manifestations of approach toward
a new state of shortrange order at the new temperature. Analysis of the kinetics indicates that very nearly a simple first-order
reaction is involved. The rate constants were found to have an activation energy of 3.18 ± 0.40 eV. By analogy with the Zener
relaxation, the temperature-change-induced short-range order which we observe is also believed to result from local atomic
rearrangements in which an average atom makes a relatively small (<10) number of jumps. Good agreement between our measured
relaxation rates and those calculated from extrapolated diffusion studies for iron, chromium, and nickel in comparable alloys
tends to substantiate the hypothesis that average atomic jump rates are being measured. 相似文献
10.
J. T. Al-Haidary A. A. Wahab E. H. Abdul Salam 《Metallurgical and Materials Transactions A》2006,37(11):3205-3214
The fatigue crack propagation rate (FCPR) in 316L austenitic stainless steel (ASS) and its weldments was investigated, at
two loading amplitudes, 7 and 8.5 kN, under tension-tension mode. Two welding techniques, submerged arc welding (SAW) and
manual arc welding (MAW), have been used. Magnetic δ-ferrite, depending upon Ni and Cr content in the metal, in the weld zone
upon solidification was considered. The ferrite number (FN) of δ-ferrite formed in the SAW zone was much higher (maximum 9.6)
compared to the corresponding value (maximum 0.75) in the MAW zone. A fatigue starter notch was positioned at different positions
and directions with respect to the weld zone, in addition to the heat-affected zone (HAZ). Regions of high and low FCPRs as
the fatigue crack propagated through and across the weld zone have been noticed. This is related to the direction of the tensile
residual stresses present in weld zone, resulting from solidification of the weld metal. The FCPR was higher along through
the HAZ and weld zone because of the microstructural change and direction and distribution of tensile residual stresses. The
FCPR was much lower when crack propagated perpendicular to the weld zone, particularly in the case of SAW in which higher
δ-ferrite volume fraction was noticed. A lower FCPR found across the weld zone, in both SAW and MAW, was accompanied by rubbed
areas in their fractures. 相似文献
11.
The micro- and macrostructures of about 50 different stainless welds of the AISI/AWS 300 series are analyzed. The results
indicate that in welding condition corresponding to a typical SMA welding those and only those welds in which the ratio Creq/Nieq≲1.48, where Nieq and Creq are the nickel and chromium equivalents on the Schaeffler diagram, solidify with the austenite as the primary or leading
phase and the delta ferrite, if any, formed from the rest melt between growing cells or cellular dendrites of the austenite.
At room temperature these welds are characterized by a regular general microstructure, soft forms of the ferrite and relatively
large compositional differences mainly caused by solidification.
T. TAKALO, formerly Research Staff Member, University of Oulu 相似文献
12.
对奥氏体不锈钢不同标距间伸长率的换算公式进行研究,结果表明:试验所得n值约为0.199,与标准中Olive公式的规定值存在一定的差异。 相似文献
13.
14.
The effect of hydrogen on the tensile behavior of austenitic stainless steel welds was studied in two AISI 300 series alloys
and two nitrogen strengthened alloys. The microstructure of these welds typically contained several percent ferrite in an
austenite matrix. Hydrogen was found to reduce the ductility of all welds; however, the severity of ductility loss increased
with increasing tendency to deform via a planar slip mode. In materials exhibiting large degrees of slip planarity, 304L and
308L, hydrogen changed the fracture mode from dimple rupture to a mixed mode of ductile and brittle fracture associated with
the austenite-ferrite interface. The two alloys, 22-13-5 and 309S, which tend to deform by cross slip mechanisms, showed smaller
losses in ductility even though hydrogen assisted the ductile rupture process by aiding void growth and coalescence, without
changing the fracture mode. Varying the amount of ferrite from approximately one to 10 pct had no significant effect on performance
in hydrogen. 相似文献
15.
《Canadian Metallurgical Quarterly》2013,52(4):277-280
AbstractThe strain-induced phase transformations produced in an austenitic stainless steel powder (Type 304L) by ball-milling at temperatures ranging from ?196° to 200°C have been studied by X-ray diffraction methods. It has been found that decreasing the temperature of deformation increases the rate of transformation of austenite to bcc martensite as well as producing more plastic deformation of the austenite. Analysis of a ball-milled 50% Fe/50% Ni alloy showed that the increased microstrain(plastic deformation) at the low temperatures was characteristic of metallic fcc materials, and not a product of the martensitic transformation. ε-martensite was found in the powders milled at ?196° and ?79°C. The value determined for Md (>200°C), which is considerably higher than any previously reported value, is considered due to the high shear forces generated in the mill Résumé Les transformations de phase dans une poudre d'acier inoxydable austénitique (type 304L) causées par la déformation lors du broyage à boulets à des températures entre ?196° et 200°C ont été etudiées par diffraction de rayons X. Une diminution de la température de déformation augmente la vitesse de la transformation austénite - martensite (c.c.) et la deformation plastique de l'austénite. Une analyse d'un alliage 50% Fe/50% Ni broyé à boulets a démontré que l'augmentation de la micro déformation à basse température était caractéristique des métaux cubiques à faces centrées que de la transformation martensitique. Les poudres broyées à ?196° et ?79°C ont présenté de la martensite ε. La valeur de Md (>200°C) trouvée est nettement supérieure aux valeurs trouvées antérieurement, probablement à cause des forces de cisaillement élevées produites dans le broyeur. 相似文献
16.
K. Borggreen und A.R. Tholen 《Metallurgical and Materials Transactions A》1976,7(10):1615-1620
In certain alloys it is possible to stop any movement of the original or strain introduced dislocations by a strong, heterogeneous
nucleation of alloying elements. Diffusion will be the only active process left to contribute to the straining during a high
temperature creep test. The dislocation structure generated before or during the nucleation process resists the deformation
for a very long time and therefore forbids a true secondary structure to develop. A creep resistant steel, UHB SS 724 LN of
the type AISI 316, has been intensively studied for the internal structure by TEM through all the three classical stages.
This steel appears to have a critical stress above which dislocations at grain boundaries are generated in the first few seconds
of the testing. The secondary creep stage is significant by showing an extremely low minimum creep rate at stresses below
the critical one contrary to the creep rate predicted by the Coble model. The steel has a very developed tertiary creep stage,
and observations of the dislocations generated by the initial straining indicate that the dislocations during this stage climb
away from the precipitated particles. The contribution from void growth to the tertiary stage will probably still exist, and
this stage therefore has at least two contributions.
相似文献
17.
Daniel P. Abraham Carl J. Altstetter 《Metallurgical and Materials Transactions A》1995,26(11):2859-2871
Microscopic observations and the results of static strain aging, stress relaxation, and strain rate change tests on 310s stainless
steel foils, with and without hydrogen, have been presented to complement the stress-strain curves in a previous article.
The hydrogen-free specimens showed minute yield points during static strain aging, while the hydrogen-containing specimens
demonstrated “preyield microstrain. ” Thermal activation analysis of the strain rate change and stress relaxation plots led
to the conclusion that the activation area for dislocation motion is decreased by hydrogen. Microstructural examination with
the scanning electron microscope (SEM) revealed extensive strain localization, while transmission electron microscopy (TEM)
studies showed microtwinning and austenite faulting in hydrogenated specimens tested at room temperature. The relation of
hydrogen-induced changes in plastic deformation to hydrogen embrittlement is discussed.
Formerly Graduate Student, Department of Materials Science and Engineering, University of Illinois at Urbana-Champaign. 相似文献
18.
In certain alloys it is possible to stop any movement of the original or strain introduced dislocations by a strong, heterogeneous nucleation of alloying elements. Diffusion will be the only active process left to contribute to the straining during a high temperature creep test. The dislocation structure generated before or during the nucleation process resists the deformation for a very long time and therefore forbids a true secondary structure to develop. A creep resistant steel, UHB SS 724 LN of the type AISI 316, has been intensively studied for the internal structure by TEM through all the three classical stages. This steel appears to have a critical stress above which dislocations at grain boundaries are generated in the first few seconds of the testing. The secondary creep stage is significant by showing an extremely low minimum creep rate at stresses below the critical one contrary to the creep rate predicted by the Coble model. The steel has a very developed tertiary creep stage, and observations of the dislocations generated by the initial straining indicate that the dislocations during this stage climb away from the precipitated particles. The contribution from void growth to the tertiary stage will probably still exist, and this stage therefore has at least two contributions. 相似文献
19.
为了研究超级奥氏体不锈钢Cr20Ni24Mo6N钢的高温变形行为,采用Gleeble热模拟试验机进行了等温压缩试验,建立了合金的热加工图。结果表明,当变形温度为1 000~1 200 ℃时,Cr20Ni24Mo6N钢的流变曲线表现出典型的“加工硬化+动态再结晶软化”特点;Cr20Ni24Mo6N钢的热激活能[Q]为678.656 kJ/mol。通过加工图与微观组织综合分析得出,超级奥氏体不锈钢Cr20Ni24Mo6N的合适热加工工艺为,应变速率10 s-1左右,应变量0.5~0.8,变形温度1 150~1 200 ℃。 相似文献
20.
针对奥氏体不锈钢成分的特殊性及可能产生的夹杂物,提出了连铸保护渣的相应研制思路,以此开发的保护渣在宝钢集团浦钢公司进行了数十炉的工业试验。结果证明,研制的奥氏体连铸保护渣各项性能均取得了较为满意的结果,铸坯质量及轧制性能达到了用户要求。 相似文献