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R.G. Faulkner 《金属学报(英文版)》2003,16(5):365-374
Irradiation-induced grain boundary segregation of solute atoms frequently bring about grain boundary precipitation of a second phase because of its making the solubility limit of the solute surpassed at grain boundaries. Until now the kinetic models for irradiation-induced grain boundary precipitation have been sparse. For this reason, we have theoretically treated grain boundary precipitation under irradiation in dilute binary alloys. Predictions of γ' -Ni3Si precipitation at grain boundaries are made for a dilute Ni-Si alloy subjected to irradiation. It is demonstrated that grain boundary silicon segregation under irradiation may lead to grain boundary γ'-Ni3Si precipitation over a certain temperature range. 相似文献
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HU Benfu University of Science Technology Beijing Beijing ChinaTAKAHASHI Heishichiro ITOH Hisatoshi TAKEYAMA Taro Hokkaido University Sapporo Japan Associate Professor Dept of Materials Science Engineering University of Science Technology Beijing Beijing China 《金属学报(英文版)》1990,3(4):229-235
The behavior of void swelling and segregation in Fe-15Cr-xMn alloys and an alloy con-taining small amount of W and V was investigated by electron-irradiation.The compositionalanalysis in the irradiated regions including grain boundaries was performed.The resultdts showthat there are many common features of irradiuation tehavior in the Fe-Cr-Mn andFe-Cr-Ni systems while there are some significant differences,In the Fe-Cr-Mn alloy sys-tems void swelling was rematrkably suppressed and at the same time the radiation-inducedsegregation was also retarded,furthermore,the segregation was strongly retarded in anFe-15Cr-15Mn alloy containing small amount of W and V.The results also show that Ni re-placed by Mn does not in general confer immunity from either swelling or phase instabilities.The phase instability is due to the different diffusion behavior of Ni and Mn in reponse to theoperation of the inverse-Kirkendall effecr.Fe segregates to the microstructural sinks in theFe-Cr-Mn alloys.The segregation of Fe often leads to the formation of ferrite.This fact isbeneficial to reducing the swelling rate and segregation on the grain boundaries. 相似文献
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This experiment investigated the role of chromium in the mechanical properties of Fe-5Mn-9Ni-5Mo-1.5Ti maraging steels containing up to 3% chromium. Remarkable age-hardening responses were observed in the Fe-5Mn-9Ni-5Mo-1.5Ti and Cr-bcaring alloys. A ductile-brittle-ductile transition occurred in the Cr-bearing alloys during isothermal aging below 510°C. This was due to the segregation of titanium and manganese to prior austenite grain boundaries and their subsequent desegregation into the matrix. The addition of chromium to the base alloy considerably improved its ductility after aging at 520°C. From microstructure and AES analyses, it is suggested that chromium addition augments the volume fractions of (Fe,Mn)2Mo and η-Ni3Ti precipitates in the Fe-5Mn-9Ni-5Mo-Cr alloys, which act as sinks of manganese and titanium in the matrices. This resulted in the reduction of the alloying elements concentration in the matrix, which is followed by the reduction in the segregation level of the elements at prior austenite grain boundaries, and consequently enhanced intergranular fracture strength. The optimum combination of strength and ductility was obtained in the Fe-5Mn-9Ni-5Mo-3Cr-l.5Ti alloy aged at 520°C for 2 hr. and was σ0 2=1721 MPa, σLS=1756 MPa. and ε,= 10.2%. 相似文献
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对Fe-30%Ni合金和超低碳贝氏体钢在高温进行不同方式变形和保温,通过变形、回复、与再结晶,获得秒同的晶体缺陷数量与构型(主要是位错分布形态)。用硼径迹显微照相技术研究了 空冷过程中硼向晶界的非平衡偏聚及与不同形态晶体缺陷的关系。结果表明,在再结晶新晶粒冷却时晶界偏聚明显。晶界附近会出现较显著的贫硼现象,而变形并回复后的原始晶粒中此现象不明显,高温回复阶段形成的多边形化亚晶界(位错墙)对冷却时硼 相似文献
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Effect of alloying elements on fracture behavior of Fe-18Ni-2Ti-(8Co) alloys has been investigated in the light of grain boundary segregation of alloying elements. During isothermal aging at 540°C, hardness level in the cobalt-bearing alloy was higher than that in the cobalt-free alloy, which is attributed to the solid solution hardening of cobalt, and the bigger hardness difference after overaging was due to the relatively fine precipitates in the cobalt-bearing alloy. The grain boundary segregation behavior of the elements was similar in two alloys, regardless of the cobalt addition. In two alloys, the fracture behavior before and after the maximum tensile strength is mainly governed by two factors: titanium at the grain boundaries and over-aging. Up to the aging time corresponding to the maximum tensile strength, the intergranular fracture strength was roughly inversely proportional to the titanium level at the grain boundaries, and after the time the tensile strength decreased with restoring ductility. Nickel or cobalt was not effective on the grain boundary strengthening of the iron-based alloys. 相似文献
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采用电子束辐照研究裂变-聚变混合反应堆预选结构材料Fe-Cr-Mn(W,V)合金的焊接热影响区(HAZ)组织损伤,测定损伤组织和晶界处的合金元素浓度变化。实验结果表明:低温下剂达10dpa,合金奥氏体组织稳定,未发现空洞形成和第二相析出;然而在高温下,剂量达4.8dpa就明显出现低密度微小空洞,并出现晶界移植现象。其次,在低温下,晶界附近大尺寸溶质原子Cr和Mn贫化,而小尺寸原子Si,V,Ni,W 相似文献
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通过扫描电镜和透射电镜分析研究了原位反应生成的TiC颗粒对喷射成形态及挤压态的Al-8.5Fe-1.4V-1.7Si合金显微组织的影响,并对合金的力学性能进行了测试。结果表明,原位反应生成的TiC颗粒均匀地分布在合金基体中并细化了基体合金的晶粒,提高了合金的高温组织稳定性;喷射成形Al-8.5Fe-1.4V-1.7Si 3.0TiC合金挤压态的室温和高温强度明显高于喷射成形Al-8.5Fe-1.4V-1.7Si合金挤压态的强度,而且塑性也有明显的提高。 相似文献
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1. IntroductionNon-equilibrium segregation of solute atoms at grain boundaries has been fOund inmany alloy systems and always been an interesting study topic. The non-equilibriumsegregation of boron at austenitic grain boundaries in low carbon steel is a typical example.A series of experimental studies indicate that the alloy system, the type and concentratiollof solute atoms, the binding energy of solute atoms with vacancies, heat treatment history,heating temperature and cooling rate have le… 相似文献
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Gorokhov V. P. Kolachev B. A. Parfenova O. A. Novikova M. B. 《Metal Science and Heat Treatment》2003,45(3-4):140-144
Boron segregation on the boundaries and in near-boundary volumes of alloy ÉI698-VD bearing up to 0.005% B and 0.01% B is investigated. The structure of fracture surfaces of impact specimens and the nature and distribution of boron carbides and borides on conventional and wide grain boundaries are described. Statistical analysis of controllable properties of production forgings with boron content in the supplied bars varying from at most 0.005% to at most 0.008% is performed. 相似文献
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The grain refinement behavior of Si-3 P,Si-25 Mn-10 P,and Al-10 Si-2 Fe-3 P master alloys on hypereutectic Al-24 Si alloy was studied.Microstructure analysis indicates that the P-containing compounds in the three master alloys are Si P,Mn P,and Al P,respectively.The coarse flower-like primary silicon in the Al-24 Si alloy transforms into smaller,well-distributed blocks with the addition of various master alloys.When pouring at 840°C,the average grain size of the primary silicon refined by Si-25 Mn-10 P master alloy with a holding time of 30 min is about 18μm,which is significantly smaller than those refined by Si-3 P and Al-10 Si-2 Fe-3 P master alloys.The grain size shows an increasing trend when the holding time is further prolonged.Higher holding temperature has a positive effect on the grain refinement of Si-25 Mn-10 P master alloy.The grain refinement mechanism of the three master alloys was also discussed. 相似文献
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《Acta Materialia》2001,49(2):289-298
Impurity effects were investigated in an Ir alloy of nominal composition Ir–0.3 W–0.006 Th–0.005 Al1. The impurities that were added included Fe, Ni, Cr, Al, and Si, at levels ranging from 50 to 5000 ppm. Of the elements investigated (impurities as well as alloying additions), only Si and Th were found to segregate to the grain boundaries. In alloys doped with low levels of Si (<200 ppm), both Si and Th segregated to the grant boundaries. In addition, Th-containing precipitates were identified in these alloys, but not Si-containing precipitates. When added at higher bulk levels, Si displaced (beneficial) Th from the boundaries. This caused the segregated Th at the boundaries to decrease (to practically zero) when the amount of grain-boundary Si increased (to its saturation level). Silicon also reacted with Th to form Ir–Th–Si precipitates and promoted the formation of a low-melting eutectic on the grain boundaries of the highest Si alloys. As for the other elements, not only did they not segregate to the grain boundaries, but they also did not affect Th segregation. Together, these results explain why Fe, Ni, Cr, Al (and Si at low levels) do not embrittle iridium, whereas Si at high levels causes severe embrittlement. 相似文献
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ZHANG Junshan CHEN Weixing CAO Zhiben Dalian University of Technology Dalian China Associate Professor Department of Materials Engineering Dalian University of Technology Dalian China 《金属学报(英文版)》1989,2(5):368-373
Creep behavior of Fe-15Cr-25Ni alloys with different grain boundary features has been in-vestigated at 850 and 950℃ and in stress range of 14.7~78.5 MPa.The single phase alloyexhibits typical recovery creep characteristics,and for the alloy in which M_(23)C_6 carbidesdensely precipitate at grain boundaries,the creep rate dramatically decreases and creep behav-ior is also significantly different from the single phase alloy.When the carbides precipitate atgrain boundaries,the dislocation density are higher and the size of subgrains near grainboundaries are smaller than those of single phase alloy.The creep mechanisms for two grainboundary features have been discussed. 相似文献
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镁偏析对铝合金晶界性能影响的计算机模拟 总被引:2,自引:1,他引:1
采用嵌入原子法对铝晶界上Mg的偏析性质及其对晶界性能的影响进行了计算机模拟。结果表明 ,Mg的晶界偏析具有自发性 ,并且降低基体的电荷密度和空位形成能 ,从而导致晶界脆化。 相似文献
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Antimony grain boundary segregation in Fe-2%Mn-Sb structure steels has been studied through measurements of the ductile-brittle transition temperature in conjunction with scanning electron microscopy, Auger electron spectroscopy and secondary ion mass spectroscopy. The research result reveals that during tempering or ageing after quenching at 980℃, Sb segregates to grain boundaries with both equilibrium and non-equilibrium natures and brings about temper embrittlement in the steels. Cerium can relieve temper embrittlement of the steels and its segregation to grain boundaries may play an important role in reducing this embrittlement. 相似文献