共查询到20条相似文献,搜索用时 46 毫秒
1.
J. K. Chen R. A. Vandermeer W. T. Reynolds 《Metallurgical and Materials Transactions A》1994,25(7):1367-1379
The kinetics of austenite decomposition were studied in high-purity Fe-0.1C-0.4Mn-0.3Si-X (concentrations in weight percent;X represents 3Ni, 1Cr, or 0.5Mo) steels at temperatures between 500 °C and 675 °C. The transformation stasis phenomenon was
found in the Fe-C-Mn-Si-Mo and Fe-C-Mn-Si-Ni alloys isothermally transformed at 650 °C and 675 °C but not in the Fe-C-Mn-Si
and Fe-C-Mn-Si-Cr alloys at any of the temperatures investigated. The occurrence of transformation stasis was explained by
synergistic interactions among alloying elements. The paraequilibrium model was applied to calculate the metastable fraction
of ferrite in each alloy. This fraction was shown to coincide with cessation of transformation in the Mo alloy transformed
at 600 °C. Transformation stasis was found in both the Ni and the Mo alloys isothermally reacted at 650 °C and 675 °C. The
interactions among Mn, Si, and Mo, as well as interactions among Mn, Si, and Ni, appear to decrease the threshold concentrations
for transformation stasis in Fe-C-Mn-Si systems. Segregation of Mn and Mo to the α/yγ boundary, assisted by the presence of
Si, was suggested to enhance the solute draglike effect (SDLE) and lead to transformation stasis. In the Ni alloy, a lower
driving force for ferrite formation resulting from the Ni addition could be responsible for the occurrence of transformation
stasis. 相似文献
2.
利用Thermo-Calc热力学计算软件得到S32760(022Cr25Ni7Mo3WCuN)超级双相不锈钢凝固过程中的相图,确定了S32760双相钢是FA (铁素体-奥氏体)凝固模式,通过改变奥氏体和铁素体的形成元素的含量,确定在不同的化学成分下的热加工性能、Cr2N和σ相析出温度,得到S32760双相钢热加工温度区间随着奥氏体形成元素C、N、Ni、Mn含量的增加而变大,随着铁素体形成元素Si、Cr、Mo含量的增加而减小,而W对热加工性能没有影响。根据热力学计算,确定了最优的化学成分(/%:0.022C,0.30Si,0.80Mn,25.60Cr,6.20Ni,0.54Cu,3.50Mo,0.54W,0.27N),S32760双相钢最佳热塑性温度为1195℃, Cr2N相的析出温度为1050℃, σ相析出温度为1020℃,热加工区间为145℃,并且通过了后续的现场实践验证。 相似文献
3.
The equilibrium conditions of four duplex stainless steels; Fe‐23Cr‐4.5Ni‐0.1N, Fe‐22Cr‐5.5Ni‐3Mo‐0.17N, Fe‐25Cr‐7Ni‐4Mo‐0.27N and Fe‐25Cr‐7Ni‐4Mo‐1W‐1.5Cu‐0.27N were studied in the temperature region from 700 to 1000 °C. Phase compositions were determined with SEM EDS and the phase fractions using image analysis on backscattered SEM images. The results showed that below 1000 °C the steels develop an inverse duplex structure with austenite and sigma phase, of which the former is the matrix phase. With decreasing temperature, the microstructure will be more and more complex and finely dispersed. The ferrite is, for the higher alloyed steels, only stable above 1000 °C and at lower temperatures disappears in favour of intermetallic phases. The major intermetallic phase is sigma phase with small amounts of chi phase, the latter primarily in high Mo and W grades. Nitrides, not a focus in this investigation, were present as rounded particles and acicular precipitates at lower temperatures. The results were compared to theoretical predictions using the TCFE5 and TCFE6 databases. 相似文献
4.
Small alterations in chemical composition, even within the boundaries of the international standards, can drastically alter the formation kinetics of intermetallic phases in a stainless steel. Therefore, by means of isothermal annealing experiments, the time‐temperature‐precipitation (TTP) diagram was constructed for an industrially cold rolled and annealed standard duplex stainless steel of type 1.4462 (X2CrNiMoN22‐5‐3), having a distinct composition. Temperature was varied from 600 to 1050 °C, with annealing times from 10 to 3·105 s Two intermetallic phases were observed with scanning electron microscopy (SEM): σ phase and χ phase. σ precipitation occurred in a slightly higher temperature range than χ precipitation. In addition, at high temperatures σ was the first phase to appear, while at lower temperatures χ was the first. This could be explained by the driving force for transformation, which is larger for σ at high temperatures and larger for χ at low temperatures. The microstructural changes during the heat treatment were studied in detail in order to provide a complete overview of all the phenomena that occur during annealing. At temperatures between 750 and 900 °C precipitation was fastest and all the α was replaced by γ and σ after prolonged times. The presence of neighbouring ferrite seems to be a necessary condition for the χ phase to be stable. The appearance of large volume fractions of σ above 700 °C was accompanied by a strong growth of the austenitic phase resulting in a more isotropic microstructure. Beneath 700 °C, the precipitated volume fractions of σ were relatively small and consequently the original banded structure remained clearly visible. At these lower temperatures the mobility of alloying elements is limited and a Widmannstätten like austenite was observed to grow into the ferrite in a needle‐like manner. 相似文献
5.
M. J. Cieslak J. A. Vandenavyle M. J. Carr C. R. Hills R. E. Semarge 《Metallurgical and Materials Transactions A》1988,19(12):3063-3069
The partitioning of alloying elements in as-solidified PH 13-8 Mo stainless steel containing up to 1.02 wt pct Pd has been
investigated. The as-solidified structure is composed of two major phases, martensite and ferrite. Electron probe microanalysis
reveals that Mo, Cr, and Al partition to the ferrite phase while Fe, Ni, Mn, and Pd partition to the martensite (prior austenite)
during solidification and cooling from the solidus. In addition to bulk segregation between phases, precipitation of the intermetallic,
PdAI, in the retained ferrite is observed. Precipitation of the normal hardening phase, β-NiAl, is also observed in the retained
ferrite. Partition ratios of the various alloying elements are determined and are compared with those observed previously
in duplex Fe-Cr-Ni stainless steel solidification structures. The martensite start temperature (Ms) was observed to decrease with increasing Pd concentration. 相似文献
6.
SONG Zhi-gang ZHENG Wen-jie FENG Han WU Zhong-zhong GUO Hai-sheng YU Fei 《钢铁研究学报(英文版)》2013,20(8):83-86
By selecting several typical duplex stainless steels (DSS), i. e., 00Cr22Ni5Mo3N, 00Cr21Ni2Mn5N and 00Cr25Ni7Mo4N, as research materials, hot ductility characteristic of DSS was studied by thermal simulation method and microstructure evolution during hot compression was observed through TEM. The results show that the optimum hot ductility temperature range of DSS is 1050–1200°C. 00Cr25Ni7Mo4N exhibits the worst hot ductility and 00Cr21Ni2Mn5N has similar hot ductility to 00Cr22Ni5Mo3N. During hot compression, the dynamic recovery of austenite occurs in DSS while the dynamic recovery and reerystallization of ferrite take place in 00Cr22NioMo3N and 00Cr21Ni2Mn5N, but only the dynamic recovery of ferrite can be observed in 00Cr25Ni7Mo4N. 相似文献
7.
Ann M. Ritter Michael F. Henry Warren F. Savage 《Metallurgical and Materials Transactions A》1984,15(7):1339-1351
Nitronic 50 and Nitronic 50W, two nitrogen-strengthened stainless steels, were heat treated over a wide range of temperatures,
and the compositions of the ferrite and austenite at each temperature were measured with analytical electron microscopy techniques.
The compositional data were used to generate the (γ + δ phase field on a 58 pct Fe vertical section. Volume fractions of
ferrite and austenite were calculated from phase chemistries and compared with volume fractions determined from optical micrographs.
Weld solidification modes were predicted by reference to the Cr and Ni contents of each alloy, and the results were compared
with predictions based on the ratios of calculated Cr and Ni equivalents for the alloys. Nitronic 50, which contained ferrite
and austenite at the solidus temperature of 1370 °C, solidified through the eutectic triangle, and the weld microstructure
was similar to that of austenitic-ferritic solidification. Nitronic 50W was totally ferritic at 1340 °C and solidified as
primary delta ferrite. During heat treatments, Nitronic 50 and Nitronic 50W precipitated secondary phases, notably Z-phase
(NbCrN), sigma phase, and stringered phases rich in Mn and Cr. 相似文献
8.
M. Ichinose F. Togashi K. Ishida T. Nishizawa 《Metallurgical and Materials Transactions A》1994,25(3):531-537
Effect of alloying elements on the morphological stability of austenite/ferrite interface formed by carburization of Fe-X alloys at 850 °C and 800 °C was investigated. Planar interfaces were found when the alloying elements added were from among the following: Ti, V, Nb, Ta, Cr, Mo, W, Co, and Cu. Nonplanar interfaces with Widmanstätten-like structures and/or an isolated phase were observed when the alloying elements were from the following group: P, Al, Sb, Ni, Mn, Si, and Ge. The degree of supersaturation of C in the α phase adjacent to the γ phase front was analyzed using the concept of local equilibrium. It was confirmed that there was indeed a close correlation between the morphological stability and the degree of C supersaturation, which in itself depended on whether the alloying element added was an α or γ stabilizer and how strongly it bonded with C in the ferrite phase. 相似文献
9.
In this study, a newly designed super ferritic stainless steel, 26Cr–4Mo–2Ni, was developed and heated to 800°C for different durations to study the precipitation behaviour of various intermetallic phases, which determined its final mechanical and corrosion resistance properties. The types, numbers and distribution of typical precipitates were investigated. Besides TiN and Nb(C,N), which are common phases formed in Ti- and Nb-stabilised ferritic stainless steel, the Laves, chi (χ) and sigma (σ) phases were also detected in the grain boundary and grain interiors, depending on the aging times . The study focused on the morphology and regularity of these intermetallic precipitates. And the effect of precipitation on the mechanical properties and the corrosion resistance were discussed. 相似文献
10.
F. Cortial J. M. Corrieu C. Vernot-Loier 《Metallurgical and Materials Transactions A》1995,26(5):1273-1286
The effects of heat treatments of the industrial type (eight-hour hold times at temperatures between 600 °C and 1000 °C) on
the structural, mechanical, and corrosion resistance characteristics of weld alloy 625 have been studied. During the heat
treatment, the mean concentration ratios of Nb, Mo, Si, Cr, Ni, and Fe elements between the interdendritic spaces and dendrite
cores show little evolution up to 850 °C. Beyond that temperature, this ratio approximates 1, and the composition heterogeneity
has practically disappeared at 1000 °C. An eight-hour heat treatment at temperatures between 650 °C and 750 °C results in
increased mechanical strength values and reduced ductility and impact strength linked to the precipitation of body-centered
tetragonal metastable intermetallic γ″ Ni3Nb phase in the interdendritic spaces. An eight-hour treatment in the temperature range between 750 °C and 950 °C has catastrophic
effects on all mechanical characteristics in relation with the precipitation, in the interdendritic spaces, of the stable
orthorhombic intermetallic δ Ni3(Nb, Mo, Cr, Fe, Ti) phase. At 1000 °C, the ductility and impact strength are restored. However, the higher the heat treatment
temperature, the weaker the mechanical strength. Heat treatments have no effect on the pitting resistance of weld alloy 625
in sea water. The comparison of the results of this study on weld alloy 625 with those previously obtained on forged metal
625 shows that heat treatments below 650 °C and above 1000 °C are the sole treatments to avoid embrittlement and impairment
of the corrosion resistance characteristics of alloy 625. 相似文献
11.
In this work, the mechanism of crack propagation during hot-rolling process of a typical medium-carbon 40Cr alloy steel is investigated by cracks characterization, thermodynamic calculation, and confocal laser scanning microscopy (CLSM). The depth of cracks is about 2.5 mm and its length along with rolling direction can even reach 2000–3000 mm. Thermodynamic calculations show that the oxide phases including MnSiO3 and MnCr2O4 can generate when the oxygen content is 0.3–1.0 wt%, suggesting that low oxygen is beneficial to the selective oxidation of Si, Mn, and Cr elements from the medium-carbon low alloy. Furthermore, in situ experiment by CLSM indicates that the submicron Cr–Mn–Si–O particles can refine austenite grains. In addition, the contents of chain proeutectoid ferrite in the steel containing Cr–Mn–Si oxides increase by 6.3% and 12.0% at the lower cooling rates of 5 and 10 °C min−1, respectively, comparing with that of no-oxide particles steel. The submicron Cr–Mn–Si–O particles can refine austenite grains, which induces the precipitation of chain proeutectoid ferrite. Thus, the serious surface cracks propagate along the chain proeutectoid ferrite with the submicron Cr–Mn–Si–O particles during the hot-rolling process. 相似文献
12.
M. Sundararaman Lalit Kumar G. Eswara Prasad P. Mukhopadhyay S. Banerjee 《Metallurgical and Materials Transactions A》1999,30(1):41-52
The microstructure of Alloy 625, which has undergone prolonged (∼70,000 hours) service at temperatures close to but less than
600 °C, has been characterized by transmission electron microscopy. The precipitation of an intermetallic phase Ni2(Cr, Mo) with Pt2Mo-type structure has been observed in addition to that of the γ″ phase. Six variants of Ni2(Cr, Mo) precipitates have been found to occur in the austenite grains. These particles exhibit a snowflake-like morphology
and are uniformly distributed in the matrix. They have been found to dissolve when the alloy is subjected to short heat treatments
at 700 °C. The occurrence of the Ni2(Cr, Mo) phase has been discussed by taking the alloy chemistry into consideration. Apart from the intermetallic phases, the
precipitation of a M6C-type carbide phase within the matrix and the formation of near continuous films, comprising discrete M6C/M23C6 carbide particles, at the austenite grain boundaries have been noticed in the alloy after prolonged service. 相似文献
13.
Metallographic studies have been conducted on a 0.024 pct C-16 pct Cr-1.5 pct Mo-5 pct Ni stainless steel to study the phase reactions associated with heat treatments and investigate the strengthening mechanisms of the steel. In the normalized condition, air cooled from 1010 °C, the microstructure consists of 20 pct ferrite and 80 pct martensite. Tempering in a temperature range between 500 and 600 °C results in a gradual transformation of martensite to a fine mixture of ferrite and austenite. At higher tempering temperatures, between 600 and 800 °C, progressively larger quantities of austenite form and are converted during cooling to proportionally increasing amounts of fresh martensite. The amount of retained austenite in the microstructure is reduced to zero at 800 °C, and the microstructure contains 65 pct re-formed martensite and 35 pct total ferrite. Chromium rich M23C6 carbides precipitate in the single tempered microstructures. The principal strengthening is produced by the presence of martensite in the microstructure. Additional strengthening is provided by a second tempering treatment at 400 °C due to the precipitation of ultrafine (Cr, Mo) (C,N) particles in the ferrite. 相似文献
14.
Low cost stainless steels where nickel is replaced in a conventional Fe‐Cr‐Ni stainless steel by manganese and nitrogen were studied. In this work, three new steels based on the system (mass %) Fe‐18Cr‐15Mn‐2Ni‐2Mo‐XN were prepared and their microstructure after each treatment was evaluated by optical and scanning electron microscopy, and X‐ray diffraction. A good correlation between texture and microstructure evolution during annealing was established. A randomization of the texture during recrystallization of the austenite was observed. Recrystallization starts at temperatures above 850°C, and after annealing for 0.5 h at 900°C, the austenite is completely recrystallized, reaching the orientation density a value near 1. Precipitation of σ ‐ phase was observed in the samples annealed at temperatures ranging from 700 to 950°C. 相似文献
15.
S. W. Thompson D. J. Colvin G. Krauss 《Metallurgical and Materials Transactions A》1996,27(6):1557-1571
Decomposition of fine-grained austenite (10-μm grain size) during continuous cooling of an HSLA-80 plate steel (containing
0.05C, 0.50Mn, 1.12Cu, 0.88Ni, 0.71Cr, and 0.20Mo) was evaluated by dilatometric measurements, light microscopy, scanning
electron microscopy, transmission electron microscopy, and microhardness testing. Between 750 °C and 600 °C, austenite transforms
primarily to polygonal ferrite over a wide range of cooling rates, and Widmanst?tten ferrite sideplates frequently evolve
from these crystals. Carbon-enriched islands of austenite transform to a complex mixture of granular ferrite, acicular ferrite,
and martensite (all with some degree of retained austenite) at cooling rates greater than approximately 5 °C/s. Granular and
acicular ferrite form at temperatures slightly below those at which polygonal and Widmanst?tten ferrite form. At cooling rates
less than approximately 5 °C/s, regions of carbon-enriched austenite transform to a complex mixture of upper bainite, lower
bainite, and martensite (plus retained austenite) at temperatures which are over 100 °C lower than those at which polygonal
and Widmanst?tten ferrite form. Interphase precipitates of copper form only in association with polygonal and Widmanst?tten
ferrite. Kinetic and microstruc-tural differences between Widmanst?tten ferrite, acicular ferrite, and bainite (both upper
and lower) suggest different origins and/or mechanisms of formation for these morphologically similar austenite transformation
products.
Formerly Graduate Student, Department of Metallurgical and Materials Engineering, Colorado School of Mines.
This article is based on a presentation made during TMS/ASM Materials Week in the symposium entitled “Atomistic Mechanisms
of Nucleation and Growth in Solids,” organized in honor of H.I. Aaronson’s 70th Anniversary and given October 3–5, 1994, in
Rosemont, Illinois. 相似文献
16.
研究了950~1 200℃60 min水冷的固溶处理对超级双相不锈钢S32750(/%:0.02C、0.49Si、1.03Mn、0.026S、0.001P、25.01 Cr、7.03Ni、3.80Mo、0.29N)12 mm板的组织、力学性能和耐蚀性的影响。结果表明,随固溶温度升高,钢中铁素体相增加,奥氏体相减少;在950℃加热时铁素体中析出大量σ-相,使钢的性能恶化,在1 050~1 100℃固溶处理后,钢中铁素体相和奥氏体相各占50%, S32750钢具有较好的综合力学性能和优良的耐蚀性能。 相似文献
17.
Apoorv Krishna Siuli Dutta Kasimuthumaniyan Subramanian Ashis K. Panda Premkumar Murugaiyan Rajat K. Roy 《Transactions of the Indian Institute of Metals》2018,71(10):2395-2402
The effect of tempering treatment has been investigated on water quenched P22 steel with the chemical composition of 0.13C, 0.24Si, 0.47Mn, 0.012P, 0.005S, 2.19Cr, 0.93Mo and balance Fe (all in wt%) within the temperature ranges of 650–900 °C. The microstructural, mechanical and magnetic properties of as-quenched and tempered steels have been investigated through optical and scanning electron microscopy, hardness and universal tensile testing, electromagnetic sensor (Magstar), respectively. The water quenched sample consists of fine martensitic structure with a hardness of 381 HV. With the progress of tempering, the martensite becomes coarse till 800 °C, decreasing the hardness of steel samples. The tempering at 700 °C results in martensite coarsening and precipitation of rod and globular shaped carbides; while a fraction of globular carbide is observed to increase in the matrix after 750 °C of tempering. Beyond 800 °C, the ferrite and bainite phases gradually form by replacing martensite, and the ferrite structure is prevalent after 900 °C. Due to microstructural changes, the magnetic properties are also affected as a function of tempering temperature. The coarsening of martensite causes the decrease in coercivity with increasing tempering temperature, leading to magnetic softening. 相似文献
18.
采用Thermo-Calc软件对022Cr21Ni2Mn5N双相不锈钢的近平衡态析出相进行了计算分析。采用光学显微镜、透射电镜、物理化学相分析方法对经中温时效处理后试验钢第二相的析出温度、种类、数量和位置进行了观察和研究,并分析了第二相析出行为对钢的冲击韧性的影响机理。结果表明:022Cr21Ni2Mn5N双相不锈钢在600~700℃中温时效时的析出相主要为六方结构的Cr_2N相和面心立方结构的M_(23)C_6相,未见σ相析出。中温时效时,受制于该钢较低的C含量,M_(23)C_6相析出位置仅局限于相界、晶界处。该钢较高的N含量促进钢中Cr_2N相析出,并在相界、晶界和铁素体晶内均有发现。时效初期M_(23)C_6和Cr_2N均具有较高的析出速度,时效时间继续延长析出量增长放缓。时效处理时间和温度直接影响钢的冲击性能:时效初期第二相的快速析出导致钢的冲击功急剧下降;时效足够长时间,第二相析出量达到饱和,钢的冲击功趋于稳定值;并且600℃长时时效时,钢的冲击功值达到最小。 相似文献
19.
V. Raghavan 《Metallurgical and Materials Transactions A》1995,26(2):237-242
The phase equilibria between austenite and ferrite in the Fe-Cr-Mn-Ni quaternary system have been computed in the temperature
range of 900 ° to 1150 °, using recent thermodynamic interaction parameters. From the computed results, the effectiveness
of Mn in replacing Ni as an austenite stabilizer has been evaluated as a function of composition and temperature. The results
show that, for 18 wt pct Cr alloys, the computed Ni equivalent of Mn is around zero and becomes negative at higher Cr contents,
which is rather surprizing. The function of Mn in 200-type stainless steels is then not so much to stabilize austenite but
to supplement the role of Cr in increasing the solubility in austenite of N, which appears to be the more important austenite-stabilizing
element. 相似文献
20.
Bikas C. Maji Madangopal Krishnan V. V. Rama Rao 《Metallurgical and Materials Transactions A》2003,34(5):1029-1042
The microstructure and phase stability of the Fe-15Mn-7Si-9Cr-5Ni stainless steel shape memory alloy in the temperature range
of 600 °C to 1200 °C was investigated using optical and transmission electron microscopy, X-ray diffractometry (XRD), differential
scanning calorimetry (DSC), and chemical analysis techniques. The microstructural studies show that an austenite single-phase
field exists in the temperature range of 1000 °C to 1100 °C, above 1100 °C, there exists a three-phase field consisting of
austenite, δ-ferrite, and the (Fe,Mn)3Si intermetallic phase; within the temperature range of 700 °C to 1000 °C, a two-phase field consisting of austenite and the
Fe5Ni3Si2 type intermetallic phase exists; and below 700 °C, there exists a single austenite phase field. Apart from these equilibrium
phases, the austenite grains show the presence of athermal ɛ martensite. The athermal α′ martensite has also been observed for the first time in these stainless steel shape memory alloys and is produced through
the γ-ɛ-α′ transformation sequence. 相似文献