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1.
D. Raabe 《Metallurgical and Materials Transactions A》1995,26(4):991-998
The microstructure and texture of a strip-cast as well as a hot-rolled austenitic stainless steel (18 pct Cr, 8.5 pct Ni)
are investigated by the use of optical metallography and quantitative X-ray texture analysis. In the hot band, a homogeneous
microstructure is revealed together with a through-thickness texture gradient consisting of a weak cold rolling type of texture
in the center layer and a shear texture close to the surface layers. The result is discussed in terms of the through-thickness
shear profile that is generated during hot rolling. In the strip-cast material, a random orientation distribution as well
as the development of martensite close to the center layer is attributed to the impingement and deformation of the films that
are solidified on the surfaces of the casting rolls. The texture close to the surface is attributed to the growth selection
of {001}〈uvw〉 oriented grains. 相似文献
2.
Strain-induced martensitic phase transformation and its influence on the formability of newly developed nitrogen-alloyed metastable austenitic stainless steels were systematically investigated. Yield strength for the asreceived steels bearing lownickel content was around 300 MPa and their elongation ratios varied from 55. 2% to61. 7%. Erichsen numbers of these samples differed from 13. 82 to 14. 57 mm. Although its Cu content was lower than that of other samples,steel D2 exhibited better plasticity and formability,which was attributed to γ→α'martensitic phase transformation. EBSD,XRD,and magnetism tests showed that increases in deformation ratio gradually increased the α' martensite phase of a sample,thereby contributing to its strain and inducing the optimal transformation-induced plasticity effect. An M_(d30/50) temperature of around 20 ℃,which is close to the deformation temperature,provided the austenite with adequate stability and gradually transformed it into martensite,thereby endowing lean ASS with better formability. 相似文献
3.
Experimental investigations were undertaken to find temperature history effects on strain-induced austenite transformation in metastable 304 stainless steel. Interrupted static tension tests were performed at temperatures 0 and — 15°C. During the first stage of deformation specimens were deformed at temperature T1. During the second stage temperature T2 was applied. Cases T1 > T2 and T1 < T2 were examined. Final amounts of α’ martensite XM were measured magnetically. A method for their summation of martensite amounts was sought for and a conclusion was obtained showing that the final amount of martensite can be calculated by the relationship XM= f(ε)|T2 where ε = εT1, + εT2 ±Δε. The corrective strain Δε depends on εT1. Its connection with true stress – true plastic strain curve at temperature T1 is discussed in this investigation. 相似文献
4.
Deformation-induced phase transformation and strain hardening in type 304 austenitic stainless steel 总被引:1,自引:0,他引:1
Amar K. De John G. Speer David K. Matlock David C. Murdock Martin C. Mataya Robert J. Comstock Jr. 《Metallurgical and Materials Transactions A》2006,37(6):1875-1886
Deformation-induced phase transformation in a type 304 austenitic stainless steel has been studied in tension at room temperature
and −50 °C. The evolution of transformation products was monitored using X-ray diffraction (XRD) line profile analysis of
diffraction peaks from a single XRD scan employing the direct comparison method. Crystallographic texture transitions due
to deformation strain have been evaluated using (111)
γ
pole figures. The tensile stress-strain data have been analyzed to explain the influence of underlying deformation-induced
microstructural changes and associated texture changes in the steel. It is found that the initial stage of rapidly decreasing
strain hardening rate in type 304 steel is primarily influenced by hcp ɛ-martensite formation, and the second stage of increasing
strain hardening rate is associated with an increase in the α′-martensite formation. The formation of ɛ-martensite is associated
with a gradual strengthening of the copper-type texture components up to 15 pct strain and decreasing with further strain
at −50 °C. Texture changes during low-temperature deformation not only change the mechanism of ɛ-martensite formation but
also influence the strain rate sensitivity of the present steel. 相似文献
5.
Kaixiang Tao Donald W. Brown Sven C. Vogel Hahn Choo 《Metallurgical and Materials Transactions A》2006,37(12):3469-3475
The strain-induced martensitic phase transformation during quasi-static uniaxial compression testing of a 304L stainless steel
was investigated at 300 and 203 K using time-of-flight neutron diffraction to study the evolution of transformation texture.
A number of specimens were precompressed to different strain levels at 300 and 203 K and the texture was investigated. At
203 K, the newly formed martensites are bcc and hcp phases and the texture analysis shows that the martensites are highly
textured due to the grain-orientation-dependent phase transformation. The bcc {100} planes are mostly oriented with their
plane-normal parallel to the loading direction at the beginning of the phase transformation and this texture is weakened during
the subsequent compressive deformation. In the case of fcc to hcp transformation, it is less dependent on the grain orientation,
although the fcc grains with {111} plane-normal at an angle close to 40 deg to the loading direction transform easier and
the {0001} plane-normal of the newly formed hcp phase tends to rotate toward the loading direction during the texture evolution.
The final texture of bcc and hcp martensites is the result of the interaction between deformation texture and transformation
texture. 相似文献
6.
以热轧态316L不锈钢为研究对象,首先利用X射线衍射仪(XRD)对其主要物相进行标定,进而利用透射电镜(TEM)的选区电子衍射和高分辨像功能确认了χ相的存在。然后利用透射电子背散射衍射技术(t-EBSD)对所有物相的分布进行表征,与常规电子背散射衍射(EBSD)的结果进行比较,准确显示了χ相的分布特征。结果表明,组织中以奥氏体基体相和带状组织为主,带状组织中主要含有σ相,还有少量的铁素体相和奥氏体相,χ相不仅存在于带状组织中,还存在于奥氏体基体中,且χ相和σ相中都富含Fe、Cr、Mo元素。 相似文献
7.
《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
8.
《Baosteel Technical Research》2010,(Z1):76
Cu precipitation behaviors in two Cu-bearing austenitic antibacterial stainless steels,type 304 and type 317L,were systematically studied by using relatively simple methods for materials analysis,including micro-hardness,electrical resistivity,electrochemical impedance spectroscopy,X-ray diffraction and differential scanning calorimetry.The results indicated that after aging at elevated temperature,the micro-hardness, electrical resistivity,electrochemical impedance and lattice constant of the steel were all varied at different degrees due to the precipitation and growth of Cu-rich phases.The results also showed that the heat evolution during the process of Cu precipitation could be sensitively detected by means of differential scanning calorimetry,obtainning the starting temperature,peak temperature,peak area of the Cu-rich precipitation,and even the activation energy by calculation.The results confirmed that the Cu-rich phased precipitation in the Cu-bearing austenitic antibacterial stainless steel should be a thermal activation process controlled by Cu diffusion.All the materials analysis methods used in this study can be more simple and effective for application in R & D of the Cu-bearing antibacterial stainless steels. 相似文献
9.
10.
Damping properties of two austenitic stainless steel grades, EN 1.4318 and EN 1.4301, were investigated. The test materials
were cold rolled to different reductions and damping capacity was measured as a function of temperature with an internal friction
method. Microstructures of the test materials were studied by means of X-ray diffraction (XRD) and magnetic measurements.
The results showed that damping capacity of the studied materials depended on the amounts of strain-induced ε- and α′-martensite phases. At temperatures around 0 °C, highest damping capacity was achieved with cold rolling reduction of 10 to
15 pct. This behavior is related to the existence of ε-martensite and stacking faults. Internal friction peak due to α′-martensite phase was present at the temperature of 130 °C. Strain aging heat treatment at 200 °C for 20 minutes decreased
the damping capacity in the entire studied temperature range. 相似文献
11.
12.
《钢铁研究学报(英文版)》2017,(12)
304 austenitic stainless steel was cold rolled in the range of 20%-80%reductions and then annealed at 700-900°C for 60 sto obtain nano/ultrafine-grained(NG/UFG)structure.Transmission electron microscopy,electron backscatter diffraction and X-ray diffraction were used to characterize the resulting microstructures.The results showed that with the increase of cold reduction,the content of martensite was increased.The steel performed work hardening during cold-working owing to the occurrence of strain induced martensite which nucleated in single shear bands.Further rolling broke up the lath-type martensite into dislocation-cell type martensite because of the formation of slip bands.Samples annealed at 800-960°C for 60 swere of NG/UFG structure with different percentage of nanocrystalline(60-100 nm)and ultrafine(100-500 nm)grains,submicron size(500-1000 nm)grains and micron size(1000 nm)grains.The value of the Gibbs free energy exhibited that the reversion mechanism of the reversion process was shear controlled by the annealing temperature.For a certain annealing time during the reversion process,austenite nucleated first on dislocation-cell type martensite and the grains grew up subsequently and eventually to be micrometer/submicrometer grains,while the nucleation of austenite on lath-type martensite occurred later resulting in nanocrystalline/ultrafine grains.The existence of the NG/UFG structure led to a higher strength and toughness during tensile test. 相似文献
13.
高氮铬锰奥氏体不锈钢有着极为广泛的应用前景,然而氮含量对其相转变的影响尚不十分清晰。设计并冶炼了氮质量分数为0.02%~1.20%的试验钢,对各钢的平衡相转变进行了热力学计算,对δ铁素体和Cr2N的形貌进行了观察。结果表明,钢中δ铁素体的最大析出量随着氮含量的升高而降低,当氮质量分数超过1.05%后,无δ铁素体析出。获得了试验钢加热时δ铁素体的析出温度与氮含量的关系式。随着氮含量的升高,试验钢在冷却时Cr2N的析出温度逐渐升高,并获得了其定量关系式。在GN04钢中,1 200 ℃等温2 h后的δ铁素体主要沿三叉晶界分布。Cr2N析出优先在晶界形成,然后朝着晶内发展。在相同等温条件下,试验钢中Cr2N的析出量随着氮含量的升高而增大,且层片间距随之减小。 相似文献
14.
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
15.
16.
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
17.
Carburization of austenitic stainless steels under paraequilibrium conditions—i.e., at (low) temperatures where there is essentially no substitutional diffusion—leads to a family of steels with remarkable properties: enhanced hardness, resulting in improved wear behavior, enhanced fatigue, and corrosion resistance, and with essentially no loss in ductility. These enhanced properties arise from an enormous carbon solubility, which, absent carbide formation, is orders of magnitude greater than the equilibrium solubility. Using interaction parameters from the latest CALPHAD assessment of the Fe-Cr-Ni-carbon system, the authors have calculated the equilibrium and paraequilibrium carbon solubility in a model Fe-18Cr-12 Ni (wt pct) austenitic steel (essentially a model 316L composition), as well as the carbon solubility in this austenite when paraequilibrium carbide formation occurs (i.e., when carbides form in a partitionless manner). For temperatures in the range 725 to 750 K, the calculations predict a paraequilibrium carbon solubility of ~5.5 at. pct. Carburization of 316L stainless steel at these temperatures, however, results in significantly higher concentrations of carbon in solid solution—up to 12 at. pct. Much better agreement with experimental data is obtained by calculating the paraequilibrium carbon solubility using Wagner interaction parameters, taken from the most comprehensive experimental study of this system. The discrepancy between the two predicted solubilities arises because the CALPHAD Cr-carbon interaction parameters are not sufficiently exothermic at the low temperatures used for paraequilibrium carburization. After multiple paraequilibrium carburization cycles, carbide formation can occur. The carbides that form under these conditions do so in a near-partitionless manner (there is modest Ni rejection to the austenite/carbide interface) and have an unusual stoichiometry: M5C2 (the Hägg or η carbide). 相似文献
18.
19.
The direction of grain boundary (GB) migration that occurs after solidification in the original surface of the weld of an
austenitic stainless steel was compared to that in the interior (the depth 100 μm from the original surface). The results are as follows. In the interior, the direction of GB migration was decided by the
moving direction of the triple junctions that bring about their equilibrium. This equilibrium results from the GB approaching
a cross angle of 120 deg with another GB in the vicinity of the triple junction. Meanwhile, in the original surface, the direction
of GB migration was decided by the direction that makes the GB plane, which is just at solidification, being perpendicular
to the surface. That is, the GB plane migrates to be perpendicular to the original surface. This GB migration was often observed
when the angle between the GB plane and the original surface had been less than 40 deg. Furthermore, the amount of the GB
migration had rapidly increased with the decrease in the angle. The validity of these results is examined with a discussion
of the reduction of the interfacial energy. 相似文献
20.