采用XRD、SEM、EDS和Image-Pro Plus金相分析等方法测定了GH3625合金热挤压管材在不同冷变形量
GH3625 alloy is a wrought nickel-based superalloy mainly used in aeronautical, aerospace, chemical, nuclear, petrochemical, and marine applications industry due to its good mechanical properties, processability, weldability and resistance to high-temperature corrosion on prolonged exposure to aggressive environments. However, in medium and high temperature environment during long-term service, the
GH3625镍基变形高温合金以析出体心四方晶体结构的金属间相
Sundararaman等[10]将Inconel 625合金在750 ℃下保温100 h后,发现其组织中有少量的
本工作对形变诱导GH3625合金热挤压管材中
本实验GH3625热挤压管化学成分(质量分数,%)为:C 0.042,Cr 21.77,Ni 60.63,Co 0.19,Mo 8.79,Al 0.21,Ti 0.40,Fe 3.68,Nb 3.75,Si 0.12,Mn 0.2,S 0.0006,P 0.006,Cu 0.06。试样从热挤压管上切取,经1150 ℃、1 h、空冷固溶处理后机加工成直径6 mm、长9 mm的圆柱试样,在应变速率为0.1 s-1条件下进行变形量ε为35%、50%和65%的室温压缩,随后进行时效处理,时效温度为800 ℃,保温时间分别为25、50、75和100 h,随后空冷。采用线切割方法将冷变形和时效处理后试样沿轴向中心剖开,进行机械研磨和抛光,用3 mL HNO3+5 mL H2SO4+90 mL HCl混合溶液化学腐蚀1~3 min。
采用Axiovert 40 MAT光学金相显微镜(OM)、Quanta FEG 450热场发射扫描电镜(SEM)、能谱仪(EDS)及Image-Pro-Plus金相分析软件,观测合金显微组织中
借助Image-Pro-Plus金相分析软件测量SEM像中
图1
GH3625合金中相析出的温度-时间-转变曲线[
Fig.1
Time-temperature-transformation diagram of the phases in GH3625 superalloy[
从
式中,
表1
不同冷变形量及时效制度下GH3625合金管材
Table 1
Mass fraction of
由
图3
冷变形GH3625合金热挤压管材中
Fig.3
SEM images (a~c) and EDS scaned along the line shown in
图4
不同保温时间下冷变形GH3625合金热挤压管材中
Fig.4
SEM images of
式中,
将
表2
不同保温时间下
Table 2
Average sizes of
图5
不同冷变形量下在800 ℃时
Fig.5
Relationship between average sizes of
图6
冷变形GH3625合金热挤压管材在800 ℃时效温度下
Fig.6
Relationship between
图7
lg[-ln(1-
Fig.7
Relationship between lg[-ln(1-
式中,
冷变形量对
图8 冷变形量和时效时间对GH3625合金热挤压管材晶粒尺寸的影响
Fig.8 Effect of cold deformation and ageing time on grain size of GH3625 superalloy hot-extruded tube
(1) 冷变形影响
(2) 冷变形GH3625合金管材在800 ℃时效过程中
(3) Nb的溶质拖曳与
The authors have declared that no competing interests exist.
[23] |
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[24] |
Following upon the general theory in Part I, a considerable simplification is here introduced in the treatment of the case where the grain centers of the new phase are randomly distributed. Also, the kinetics of the main types of crystalline growth, such as result in polyhedral, plate-like and lineal grains, are studied. A relation between the actual transformed volume V and a related extended volume Vis derived upon statistical considerations. A rough approximation to this relation is shown to lead, under the proper conditions, to the empirical formula of Austin and Rickett. The exact relation is used to reduce the entire problem to the determination of V, in terms of which all other quantities are expressed. The approximate treatment of the beginning of transformation in the isokinetic range is shown to lead to the empirical formula of Krainer and to account quantitatively for certain relations observed in recrystallization phenomena. It is shown that the predicted shapes for isothermal transformation-time curves correspond well with the experimental data.
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[1] |
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[2] |
Microstructures and a microstructural, columnar architecture as well as mechanical behavior of as-fabricated and processed INCONEL alloy 625 components produced by additive manufacturing using electron beam melting (EBM) of prealloyed precursor powder are examined in this study. As-fabricated and hot-isostatically pressed ("hipped") [at 1393 K (1120 °C)] cylinders examined by optical metallography (OM), scanning electron microscopy (SEM), transmission electron microscopy (TEM), energy-dispersive (X-ray) spectrometry (EDS), and X-ray diffraction (XRD) exhibited an initial EBM-developed γ″ (bct) NiNb precipitate platelet columnar architecture within columnar [200] textured γ (fcc) Ni-Cr grains aligned in the cylinder axis, parallel to the EBM build direction. Upon annealing at 1393 K (1120 °C) (hot-isostatic press (HIP)), these precipitate columns dissolve and the columnar, γ, grains recrystallized forming generally equiaxed grains (with coherent {111} annealing twins), containing NbCrlaves precipitates. Microindentation hardnesses decreased from 2.7 to 2.2 GPa following hot-isostatic pressing ("hipping"), and the corresponding engineering (0.2 pct) offset yield stress decreased from 0.41 to 0.33 GPa, while the UTS increased from 0.75 to 0.77 GPa. However, the corresponding elongation increased from 44 to 69 pct for the hipped components.
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This paper presents an investigation of laser rapid manufacturing (LRM) for Inconel-625 components. LRM is an upcoming rapid manufacturing technology, it is similar to laser cladding at process level with different end applications. In general, laser-cladding technique is used to deposit materials on the substrate either to improve the surface properties or to refurbish the worn out parts, while LRM is capable of near-net shaping the components by layer-by-layer deposition of the material directly from CAD model. In the present study, a high-power continuous wave (CW) CO laser system, integrated with a co-axial powder-feeding system and a three-axis workstation were used. The effect of processing parameters during LRM of Inconel-625 was studied and the optimum set of parameters for the maximum deposition rate was established employing Orthogonal L9 array of Taguchi technique. Results indicated that the powder feed rate and the scan speed contributed about 56% and 26%, respectively to the deposition rate, while the influence of laser power was limited to 10% only. Fabricated components were subjected to non-destructive testing (like鈥攗ltrasonic testing, dye-penetrant testing), tensile testing, impact testing, metallographic examinations and micro-hardness measurement. The test results revealed defect-free material deposition with improved mechanical strength without sacrificing the ductility.
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[5] |
Aging behavior of Inconel 625 has been studied at 540 °C. The Ni 2 (Cr,Mo) phase, found in this material only after a long service life, has been detected along with the γ ″ phase after a short aging. Acoustic emission technique has been found sensitive enough to detect early stages of precipitation.
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[6] |
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[7] |
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[8] |
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″ Ni 3 Nb 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 Ni 3 (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.
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[9] |
The microstructural evolutions occurring upon thermal aging of alloy 625 sheets were studied in the 823 K to 1173 K (550 °C to 900 °C) temperature range and for durations up to 2000 hours. TTT diagrams of the δ and γ″ phases were established based on high-resolution scanning electron microscopy and associated quantitative image analysis approaches. The evolutions of secondary carbide volume fraction were also characterized. It was observed that the precipitation domains of the γ″ and δ phases are, respectively, 823 K to 1023 K (550 °C to 750 °C) and 923 K to 1173 K (650 °C to 900 °C) and that the γ″ coarsening follows the LSW theory once these particles have an ellipsoidal morphology. The onset of grain growth, accompanied with an increase of the texture index, was observed at a temperature as low as 1173 K (900 °C). It results from the progressive dissolution of grain boundaries' secondary carbides (especially MC carbides) at this temperature, a process that favors a greater mobility of grain boundaries. It is also shown that the forming process (shear spinning), even after a relaxation heat treatment, enhances and stabilizes the precipitation of the δ phase compared to as-rolled + solution heat-treated sheets. It hence slows down the precipitation of the γ″ phase, a result that is in good agreement with a thermal aging that was performed under load ( i.e., during a creep test).
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[10] |
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[11] |
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[12] |
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[13] |
[本文引用:1]
研究了冷加工变形量对GH625合金板材力学性能的影响.研究表 明,随冷加工变形量的增加,GH625合金的拉伸强度增加,但塑性降低.冷加工变形量对持久寿命和冷热疲劳性能影响显著,20%左右的冷变形量可使合金具 有最佳的持久寿命和疲劳性能及良好的综合力学性能.合金冷作硬化效果与合金的回复和再结晶程度及固溶处理温度有关.
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[16] |
Abstracts are not published in this journal
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[18] |
The segregation of niobium in Inconel 718 was investigated by means of X-ray diffraction. It was found that the very weak and diffuse profiles of sidebands on the lower angle side of γ phase (2 0 0), (2 2 0), (3 1 1), (2 2 2) diffraction peaks were observed in the X-ray diffraction patterns of Inconel 718 cold rolled to 25% reduction, and then solution treated at 1040 °C, 970 °C and aged (DA). The formation of sidebands was contributed to the Nb segregation in the γ matrix. The composition of the Nb rich region was estimated according to the lattice parameter of the Nb rich region. The results showed that the degree of Nb segregation in the matrix is less than that at the grain boundries.
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[19] |
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[20] |
Inconel 718 (IN718) is a nickel base alloy widely used in the aerospace industry due to its mechanical stability at elevated temperatures. Stable δ phase with acicular morphology weakens the IN718, however, it has been found that a spherical morphology distributed in the grain boundaries acts as an anchor preventing grain growth during hot deformation. The delta processing (DP718) is a saturation of δ phase in the alloy by thermal treatment followed by thermomechanical working to control the grain growth and morphology during deformation. Two specimens (A and B) of IN718 alloy were solubilized for 1h at 1100°C WQ and aging at 900°C for 24hWQ thermal treatment, following bythermomechanical deformation. Sample A was deformed at 0.001 s -1 and sample Bat 0.01 s-1, both deformations were carried out at 960°C and the final microstructures were characterized by optical microscopy and scanning electron microscopy (SEM) in order to evaluate morphology and grainsize distribution.
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[21] |
[本文引用:1]
采用X射线衍射技术测定了Inconel 718合金s相含量,研究了冷轧变形对δ相形貌、分布及数量的影响。结果表明,在ε=25%变形条件下,δ相首先在初始孪晶界及晶界上析出,随后在再结晶晶界上及晶内析出;在ε≥40%变形条件下,δ相首先在初始孪晶界、晶界及变形带上析出,并且随冷轧变形量增加,在变形带上的析出量增加。在910℃保温4 h条件下,随冷轧变形量增加,δ相析出形貌由针状逐渐变为颗粒状。冷轧变形促进了δ相析出。
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[22] |
The microstructures of five commercially available nickel-based superalloys (NIM80A, NIM90, NIM105, IN738, IN939) have been studied after heat-treatments at 4 different temperatures and for times up to 15 000 h (170 samples). In all cases for moderate times and temperatures the mean γ′ dimension increased linearly with the cube root of time with an activation energy of 250 to 272 kJ mol 611 K 611 . However, at high values of time and temperature some deviations from this behaviour were observed on two of the superalloys. These were accompanied by marked morphological changes thought to be due to re-solution effects. Extended analysis of the particle-size distributions suggests a correlation with the distribution functions predicted by the Lifschitz-Slyosov theory modified to take account of encounters between growing particles. The microstructural data so obtained have been used in failure diagnosis. Attempts have been made to explain the changes in γ′ shape with respect to long-term composition.
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[本文引用:1]
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[27] |
Addiert man zur freien Energie einen geeignet definierten elastischen Energieterm, dann erh01lt man eine neue Funktion für die freie Energie, die in einem begrenzten Konzentrationsbereich alle Eigenschaften eines thermodynamischen Potentials für koh01rente Prozesse besitzt. Sie kann z.B. zur Bestimmung des entsprechenden Phasendiagramms nach der üblichen Tangentenmethode benutzt werden. Hier wird sie verwendet, um die koh01rente Keimbildung in isotropen Festk02rpern zu untersuchen, insbesondere in der N01he der Metastabilit01tsgrenze, wo diese Keimbildung nicht mehr klassisch ist.
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[28] |
Not Available
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