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1.
H. Leitner M. SchoberR. Schnitzer S. Zinner 《Materials Science and Engineering: A》2011,528(15):5264-5270
In the present work a Ti-free and Ti-containing stainless maraging steel of type PH13-8 Mo were investigated with respect to their mechanical properties. Particular attention was given to the stress-strain behavior during tensile tests in correlation to the developed precipitates and austenite at differently aged conditions. Both alloys show a strong increase in strength from the very beginning of aging with the typical stress-strain behavior of maraging steels, whereas the Ti-containing alloy suffers from severe intergranular embrittlement at short aging times. Embrittlement of the Ti-containing steel grade is attributed to the significantly higher volume fraction of precipitates in the early stages of aging when compared to the Ti-free steel grade. Overaging leads to distinct work hardening in the Ti-containing alloy, which is caused by the evolution of the precipitates and the formation of reverted austenite. 相似文献
2.
Jialong Tian M. Babar Shahzad Wei Wang Lichang Yin Zhouhua Jiang Ke Yang 《材料科学技术学报》2018,34(9):1671-1675
The effect of Co addition on the formation of Ni-Ti clusters in maraging stainless steel was studied by three dimensional atom probe (3DAP) and first-principles calculation. The cluster analysis based on the maximum separation approach showed an increase in size but a decrease in density of Ni-Ti clusters with increasing the Co content. The first-principles calculation indicated weaker Co-Ni (Co-Ti) interactions than Co-Ti (Fe-Ti) interactions, which should be the essential reason for the change of distribution characteristics of Ni-Ti clusters in bcc Fe caused by Co addition. 相似文献
3.
Ronald Schnitzer Rene Radis Matthias Nöhrer Michael Schober Rainer Hochfellner Silvia Zinner E. Povoden-Karadeniz Ernst Kozeschnik Harald Leitner 《Materials Chemistry and Physics》2010
The mechanical properties of maraging steels are strongly influenced by the presence of reverted austenite. In this study, the morphology and chemical composition of reverted austenite in a corrosion resistant maraging steel was characterized using transmission electron microscopy (TEM) and atom probe tomography (APT). Two types of austenite, i.e. granular and elongated, are present after aging at 575 °C, whereby the content of the latter increases during aging. The investigations revealed that the austenite phase is enriched in Ni, which prevents the transformation to martensite during cooling. Inside and next to the austenitc areas, Mo and Cr-rich carbides, which form during the aging treatment, were found. Various aging treatments were performed to obtain the activation energy for the formation of reverted austenite. Additionally, the experimental data are compared with thermodynamic and kinetic simulations. Based on these results and the chemical composition changes of the phases, a model for the formation of reverted austenite is presented. It is concluded that precipitation of B2-ordered NiAl and formation of reverted austenite take place simultaneously during aging and that dissolution of precipitates is not essential for the initial formation of reverted austenite. 相似文献
4.
利用热力学计算软件Thermo-Calc,研究了马氏体时效不锈钢Fe-13Cr-7Ni-4Mo-4Co-2W在不同温度下的基体组织和析出相的变化.通过TEM、SADP法分析研究了马氏体时效不锈钢在固溶处理与时效处理过程中显微组织与析出行为.热力学计算与实验研究结果一致表明,马氏体时效不锈钢高温析出Laves-Fe2Mo相,固溶温度超过1050℃,Laves-Fe2Mo相全部溶解;时效析出R相,其含量在8%左右.根据计算结果优化了相应的热处理工艺,力学性能研究结果表明,用所确定的时效工艺进行热处理后,马氏体时效不锈钢的强韧性最好. 相似文献
5.
针对一种以Al作为主要强化元素的新型马氏体时效不锈钢,通过力学性能测试、光学显微镜观察和透射电子显微分析方法,研究不同的热处理温度对实验钢力学性能和微观组织的影响。结果表明:该实验钢的抗拉强度最高可达1876MPa,屈服强度可达1762MPa,具有良好的强韧性配合。固溶处理后形成了具有高密度位错的细小板条马氏体组织,在时效过程中,马氏体基体上弥散析出的NiAl相使其强度得到大幅度的提升。随着时效温度的提高,NiAl析出相颗粒逐渐长大粗化,从而使强度在到达峰值后迅速下降,出现了过时效现象。实验钢经过820℃固溶+(-70℃)冷处理+540℃时效处理后可获得良好的综合力学性能。 相似文献
6.
Axel Stupnik 《Vacuum》2007,82(2):170-173
The local elemental composition and morphology of stainless steel surfaces before and after high-temperature bake out (vacuum firing) has been investigated by atom probe (AP) and scanning tunnelling microscopy (STM). The AP depth profiling analysis show significant surface enrichment of nickel after vacuum firing. The surface of AISI 304L stainless steel sheet samples imaged by STM show a significant reconstruction after vacuum firing. Large (1 1 1) terraces with up to 200 nm in width bounded by bunched steps and facets can be observed in the STM micrographs. 相似文献
7.
General economic and metallurgical requirements, and processing methods for coinage materials are reviewed. The Indian effort
at the development of ferritic stainless steels for coinage is discussed. The results of several trials at the Salem Steel
Plant towards establishing the appropriate composition and processing route are presented and evaluated. 相似文献
8.
A ferritic steel with finely dispersed precipitates was investigated to reveal the fundamental strengthening mechanisms. The steel has a yield strength of 760 MPa, approximately three times higher than that of conventional Ti-bearing high strength hot-rolled sheet steels, and its ultimate tensile strength reaches 850 MPa with an elongation-to-failure value of 18%. Using energy dispersive X-ray spectroscopy (EDXS) and transmission electron microscope (TEM), fine carbides TiC with an average diameter of 10 nm were observed in the ferrite matrix of the 0.08%Ti steel, and some cubic M23C6 precipitates were also observed at the grain boundaries and the interior of the grains. The finely dispersed TiC precipitates in the matrix provide matrix strengthening. The estimated magnitude of precipitation strengthening is around 458 MPa, depending on the average size of the nanoscale precipitates. Dislocation densities increased from 3.42 × 1013 m−2 to 1.69 × 1014 m−2, respectively, with increasing tensile strain from 5.5% to 22%. The measured work-hardening behavior can be related to the observed dislocation accumulations resulting from the dispersed nano-scale precipitates. 相似文献
9.
S. Hossein Nedjad M. Nili Ahmadabadi T. Furuhara 《Materials Science and Engineering: A》2008,490(1-2):105-112
Evolution of the intergranular brittleness of an Fe–10Ni–7Mn (weight pct) maraging steel was correlated with precipitation reactions during isothermal aging at 753 K. Intergranular brittleness of the Fe–Ni–Mn steel raises after aging treatment which occurs catastrophically at zero tensile elongation in the underaged and peakaged steels. The intergranular failure is attributed to grain boundary weakening due to the formation of coarse grain boundary precipitates associated with solute-depleted precipitate-free zones during isothermal aging. Further, evidences of planar slip bands were found within the grains of a peakaged specimen loaded by tensile deformation. Those inhomogeneously deformed bands were identified to apply large strain localization in the soft precipitate-free zones at grain boundaries which is assumed to fascinate microcracks initiation at negligible macroscopic strains in the underaged and peakaged steels. During further aging, concurrent reactions including (i) overaging of matrix precipitates, (ii) spheroidization of grain boundary precipitates, (iii) growth of precipitate-free zone in width and (iv) diffusional transformation to austenite take place which increase tensile ductility after prolonged aging. 相似文献
10.
铜离子注入AISI 304不锈钢的抗菌性能研究 总被引:7,自引:2,他引:7
铜离子由金属蒸汽真空弧(MEVVA)离子注入机引出注入AISI 304不锈钢,采用100keV的能量、(1.0~8.0)×1017ions/cm2的注入剂量。抗菌实验结果表明,铜离子注入试样具有良好的抗大肠杆菌的效果,抗菌处理使得试样具有优良的抗大肠杆菌和金黄色葡萄球菌的效果,且注入量接近饱和注入量时,样品具有最佳的抗菌性能。用小掠射角X射线衍射(GXRD)和透射电镜(TEM)分析了注入层相组成和微观组织,结果表明铜离子注入样品经特殊抗菌处理后,注入层生成了细小分散的富铜相,析出的富铜相使得试样具有优良的抗菌效果。 相似文献
11.
Gerald A. Zickler Ronald Schnitzer Rene Radis Rainer Hochfellner Ralf Schweins Martin Stockinger Harald Leitner 《Materials Science and Engineering: A》2009,523(1-2):295-303
ATI Allvac® 718Plus™ is a novel nickel-based superalloy, which was designed for heavy-duty applications in aerospace turbines. In the present study the high-resolution investigation techniques, atom probe tomography, electron microscopy and in situ high-temperature small-angle neutron scattering were used for a comprehensive microstructural characterization. The alloy contains nanometer-sized spherical γ′ phase precipitates (Ni3(Al,Ti)) and plate-shaped δ phase precipitates (Ni3Nb) of micrometer size. The precipitation kinetics of the γ′ phase can be described by a classical model for coarsening. The precipitation strongly influences the mechanical properties and is of high scientific and technological interest. 相似文献
12.
Hybrid (plasma + gas tungsten arc) weldability of modified 12% Cr ferritic stainless steel 总被引:1,自引:0,他引:1
This paper deals with the hybrid (plasma + gas tungsten arc) welding properties of 12 mm thick modified 12% Cr ferritic stainless steel complying with EN 1.4003 and UNS S41003 steels with a carbon content of 0.01% to improve the weldability. The root passes of the butt welds were produced with plasma arc welding (PAW) without filler metal while gas tungsten arc welding (GTAW) was used to accomplish filler passes with 309 and 316 austenitic stainless steel type of consumables, respectively. The joints were subjected to tensile and bend tests as well as Charpy impact toughness testing at −20 °C, 0 °C and 20 °C. Examinations were carried out in terms of metallography, chemical analysis of the weld metal, ferrite content, grain size and hardness analyses. Although 309 consumables provided higher mean weld metal toughness values compared to 316 (90 J vs. 75 J), 316 type of consumables provided better mean HAZ toughness data for the joints (45 J vs. 20 J) at −20 °C. Toughness properties of the welds correspond with those of microstructural features including grain size and ferrite content. 相似文献
13.
《Materials at High Temperatures》2013,30(1):36-42
AbstractOver the past few years, car manufacturers have been considering ever higher service temperatures for the engine in order to comply with the constraints of depollution standards. The requirements in terms of exhaust gas temperature could easily reach and overtake the limits of common stainless steel grades used for such applications in the coming years.A new ferritic stainless steel – named K44X – with increased high temperature resistance has therefore been developed to withstand service temperature up to 1000 °C. K44X belongs to EN 1.4521 and AISI 444 classifications and is composed of approximately 19% Cr, 2%Mo and 0.6% Nb. This specific composition leads to better mechanical properties, higher creep and fatigue resistance than EN 1.4509, while keeping comparable weldability and formability. Its coefficient of thermal expansion is lower in comparison to austenitic stainless steel grades and its resistance to cyclic oxidation is improved significantly.High-temperature properties (mechanical properties, creep, cyclic oxidation resistance, and high cycle fatigue) of K44X are presented in this paper and compared with common ferritic and austenitic stainless steels used in the hot end of exhaust lines. A thermal fatigue test – designed to reproduce exhaust manifold service conditions – has also been carried out with the highest temperatures of the cycle in the range of 850–1000 °C. The results of these thermal fatigue tests were compared with the above-mentioned stainless steels. A thermal fatigue damage criterion was then identified based on these experimental results and using a cyclic behaviour law obtained from isothermal low cycle fatigue tests. 相似文献
14.
Kyung Jun Lee Min Sung Chun Myung Hyun Kim Jae Myung Lee 《Computational Materials Science》2009,46(4):1152-1162
A series of uniaxial tensile test under cryogenic temperature was carried out for AISI 304 and 316 austenitic stainless steels (ASS) in this study. Typical non-linear hardening phenomena under the cryogenic environment, such as transformation induced strain hardening and threshold strain for the 2nd hardening, has been observed in a quantitative manner.The important factors affecting the non linear material behavior of austenitic stainless steel including phase transformation, discontinuous yielding and micro-damage are modeled using constitutive equations system based on strain decomposition at the small strain formulation. A strong nonlinearity of strain hardening is described using the coupling of modified Bodner’s plasticity model and phase transformation induced strain model. The strain (threshold strain for onset of 2nd hardening) dependent plasticity model was proposed in the hardening function of Bodner’s model. In order to explicitly express the phase transformation induced strain, TI model (Tomita and Iwamoto model [Y. Tomita, T. Iwamoto, Constitutive modeling of TRIP steel and its application to the improvement of mechanical properties, International Journal of Mechanical Sciences 37 (1995) 1295–1305.]), which is a function of accumulated plastic strain and volume fraction factor of martensite, is selected in this study.Also the unified damage model, which can be connected with elasto-plastic constitutive equation developed in this study, is suggested, and the utility of proposed model was validated by the comparison between experiments and numerical evaluations. 相似文献
15.
16.
Dongdong Dong Cheng Chang Hao Wang Xingchen Yan Wenyou Ma Min Liu Sihao Deng Julien Gardan Rodolphe Bolot Hanlin Liao 《材料科学技术学报》2021,73(14):151-164
In the present work,selective laser melting (SLM) technology was utilized for manufacturing CX stainless steel samples under a series of laser parameters.The effect of laser linear energy density on the microstructure characteristics,phase distribution,crystallographic orientation and mechanical properties of these CX stainless steel samples were investigated theoretically and experimentally via scanning electron microscope (SEM),X-ray diffraction (XRD),electron backscatter diffraction (EBSD) and transmission electron microscope (TEM).Based on the systematic study,the SLM CX stainless steel sample with best surface roughness (Ra =4.05 ± 1.8 μm) and relative density (Rd =99.72 %±0.22 %) under the optimal linear density (η=245 J/m) can be obtained.SLM CX stainless steel was primarily constituted by a large number of fine martensite (α'phase) structures (i.e.,cell structures,cellular dendrites and blocky grains) and a small quantity of austenite (γ phase) structures.The preferred crystallographic orientation (i.e.,<111 > direction) can be determined in the XZ plane of the SLM CX sample.Furthermore,under the optimal linear energy density,the good combinations with the highest ultimate tensile strength (UTS =1068.0 %±5.9 %) and the best total elongation (TE =15.70 %±0.26 %) of the SLM CX sample can be attained.Dislocation strengthening dominates the strengthening mechanism of the SLM CX sample in as-built state. 相似文献
17.
Keum-Oh Lee Seong-Gu Hong Samson Yoon Soon-Bok Lee 《International Journal of Fatigue》2005,27(10-12):1559
Low-cycle fatigue tests on 429EM ferritic stainless steel and 316L austenitic stainless steel were carried out in a wide range of temperatures from room temperature to 750 °C. The Tomkins fatigue life model was applied to correlate the fatigue life with crack propagation rate and this model matched well with the fatigue life of 429EM stainless steel but not for the 316L stainless steel. A new life prediction model was developed to consider the temperature effect on fatigue life. The predictions show good agreement with experimental results for both materials. The predicted lives were within a±2X scatter band at all test temperatures. 相似文献
18.
A conceptual approach was used to design a new Ni-free austenitic stainless steel with a unique combination of ultrahigh strength and ductility. The concept was based on the alloying of the 0.05C–18Cr–12Mn (wt.%) steel by 0.39%N and heavy warm rolling (84% reduction) at 1173 K (900 °C) to achieve the yield strength of minimum 1 GPa and high tensile strength and elongation due to a proper stability of the austenite as a result of the optimized stacking fault energy (SFE). The yield strength of 1010 MPa, tensile strength of 1150 MPa and high fracture strain of 70% were measured for the steel designed. Dislocation and solid solution hardening mechanisms are introduced as the main contributors for the ultrahigh yield strength of the steel. The strain hardening is gradual and the hardening rate reaches a high level of ∼2400 MPa at a high true strain of 40% due to slow α′-martensitic transformation and mechanical twinning. Consequently, the ductility of the designed steel is excellent. 相似文献
19.
Most of the conventional strengthening methods for metals and alloys such as work hardening, precipitation hardening, cause a decrease in ductility and are not very effective for cyclic loading. In this study, a new strengthening method, which is effective for high cycle fatigue, has been developed. The intersections of dislocations in a stainless steel are freezed by very fine martensite particles, which are supposed to suppress dislocation motion at low stress amplitudes. Fatigue life in a high cycle regime increased >60 times, and no decrease in ductility was observed in tensile tests, as compared to a work-hardened stainless steel. 相似文献
20.
A cellular automaton modeling was developed to investigate the growth kinetics of Cr-rich carbides’ precipitation and the three dimensional distribution of Cr concentration. The effects of solution treatment conditions and sensitization temperatures on Cr depletion were studied in detail. The results indicated that the amount of precipitate increased as sensitization temperature increased, decreasing along with the solution treatment temperature. Furthermore, the changing tendency of the precipitate’s amount was in accordance with that of the degree of sensitization (DOS) obtained from the samples treated at the corresponding conditions. 相似文献