核动力工程

Study on Precipitation Reaction between Nitrate Thorium and Salvolatile

LONG Dijun, LIU Jinhong, WANG Xiaomin, PENG Xiaoming

2012, 33(S2): 1-3,8.

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In this study,the effect of pH and nitrate thorium concentration on the precipitation ratio of thorium was investigated.Also,the effect of temperature,precipitator adding velocity and ageing on the form of precipitate was studied.The result shows that the precipitation ratio increased with the increasing of pH value on the condition of pH＜5.3;when the pH＞5.3,the precipitation ratio decreased with the increasing of pH value,and the precipitation return to dissolve evidently when the pH＞7.The form of thorium precipitate is amorphous.Adjusting the reaction temperature,the velocity of adding precipitate and the time of ageing could not make the amorphous precipitate transform into crystal precipitate.

Preparation of（Th,U）O₂ Microspheres by Sol-gel Process

WANG Xinjie, YIN Rongcai, LU Zhangxian

2012, 33(S2): 4-8.

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(Th,U)O₂ microspheres were prepared by sol-gel process through hexamethylenetetramine（HMTA）-urea system.Gelling temperature,washing and calcination route were studied under different Th/（Th+U）.Microspheres were sintered at different temperature and the microstructure were studied by met-alloscope（MS） and scanning electron microscope（SEM）.The results showed that the internal gelation method could be applied well in preparing（Th,U）O₂ microspheres with the Th/（Th+U） ratio no higher than 0.5;compacted（Th,U）O₂ microspheres were gained at sintering temperature between 1200℃and 1500℃,and the density could reach 99% of TD.The SEM results showed that ThO₂ and UO₂ had formed well-proportioned solid solution with pores tiny and homogeneous distribution.

Fission Gas Model for UO₂ Fuels Considering Bubble Coalescence and Grain Boundary Diffusion

CUI Yi, DING Shurong, ZHAO Yunmei, HUO Yongzhong, WANG Canglong, YANG Lei

2012, 33(S2): 9-12,42.

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Based on the modified Booth model,the micro-scale governing equations for both the fission gas release and the gaseous swelling are established,considering the grain boundary resolution,the inter-granular bubble coalescence,the intragranular gas diffusion and the effect of hydrostatic pressure.The nu-merical method for solving the governing equations is developed,and the code for predicting the behavior of the fission gas in the nuclear fuel is built.By comparing the numerical results with the experimental data,the model in this paper is validated.

Research on Hoop Tensile Test Method for N36 Zirconium Tube

YAN Meng, PENG Qian, WANG Pengfei, ZHAO Wenjin

2012, 33(S2): 13-16.

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Hoop tensile test methods performed on ring specimen of N36 zirconium cladding are studied and the effect of factors like sample shape is analyzed adopting matching radius mandrels to put hoop tensile load on ring specimen.Orientation of specimen affects the stress level,friction between mandrels and sample will increase tensile stress.Influence of bend effect of gauge section on tensile strength can be ignored.Analysis of hoop tensile test curve is similar to ways on regular tensile test curve,but displacement need to be revised.

Study on Microstructure and Texture of Processed N18 Plates by EBSD

DAI Xun, LIU Hong, WANG Pengfei, WANG Ying, ZHAO Wenjin

2012, 33(S2): 17-21.

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The evolution of grain structure,grain boundary characterization and texture are studied by EBSD auto analysis technique in an SEM on N18 plates,which were rolled at 750,780 and 820℃,respectively,then cold rolled,and finally annealed at 580℃.The results show that dynamic recovery and recrystallization occur during N18 alloy plates hot rolling and a lot of disfigurements such as low angle grain boundaries and sub-structure are produced.Furthermore,the density of recrystallized nucleation and disfigurements increases with the increasing of rolling temperature.During recrystallization,the density of disfigurements decreases with the increasing of recrystallization time,but still higher than as-received plates,which illustrates that the plates are incompletely recrystallized.The $\{10 \quad \overline{1} 1\}<\overline{1} 0 \quad 12>$ pressure twinning is detected in hot rolling specimens,which illustrates that the pressure twinning can promote the hot rolling deformation in N18 alloy plates.During recrystallization,the density of basal texture decreases with the prolonging of heat preservation time,but the pyramidal texture do not change too much.

Nodular Corrosion Investigation of N18 Zirconium Alloys

LI Qiang, HUANG Changjun, YANG Yanping, XU Long, LIANG Xue, ZHOU Bangxin

2012, 33(S2): 22-27,38.

Abstract(10) PDF(1)

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In the present work,the nodular corrosion properties in the steam（500 oC/ 10.3 MPa） of N18 zirconium alloys after different heat treatment were investigated.The nodular corrosion of N18 alloys was liable to occur after α +β binary phases at 780oC and α uniary phase treatment at 700oC.Microstructure ob-servation found that the dilution of alloying element（especially Nb） at high temperature contributed the dete-rioration of nodular resistance.Furthermore,the formed alloying elements depleted zone could not be elimi-nated effectively by large deformation or low-temperature annealing treatment.A sufficient solution treat-ment at β phases has been proved as an effective way to eliminate the alloying elements depleted zone.

Review of Investigations on Anisotropic Creep Behavior of Zr Alloy Cladding

WANG Pengfei, ZHAO Wenjin, YAN Meng

2012, 33(S2): 28-34.

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The present situation of the related experimental and numerical simulation investigations on creep anisotropy of Zr alloy cladding is reviewed.In this paper the numerical simulation methods on creep anisotropy are introduced emphatically.Moreover,results on the investigation of anisotropic creep behavior,which based on lower and upper boundary and self-consistent three polycrystalline model,are summarized.Some suggestions on future research in this related fields in China are proposed.

Vickers Micro-Hardness Analysis of Irradiated Zr-2 Alloy Tube

FU Yuanjie, ZHANG Haisheng, HUANG Juan, LI Furong, CUI Yonghai, SUN Kai

2012, 33(S2): 35-38.

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This paper studied the Vickers micro-hardness of irradiated Zr-2 alloy tube and analyzed the irradiation performance of fuel cladding material.The analysis shows that the hardness has the same change tend to the tensile strength,and the irradiation strengthening is obvious for Zr-2 alloy material.Fitting a curve of ferrous metals’ hardness and tensile strength,the Vickers micro hardness of Zr-2 alloy is calculated through tensile strength.

Effect of Second-Phase Particles on Corrosion and Hydrogen Absorption Property of N36 Claddings in 500℃ Steam

CHEN Liang, YANG Zhongbo, MIAO Zhi, ZHAO Wenjin, DAI Xun, SUN Chao

2012, 33(S2): 39-42.

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Two types of N36 cladding tubes were exposed to 500℃,10.3MPa superheated steam for 500 hours.The characteristics of the second-phase particles and the oxide layer formed on N36 claddings were analyzed by scanning electronic microscope.The corrosion kinetics show that the nodular corrosion resistance of specimen A is better than that of specimen B.In anaphase of corrosion,it is shown the effect of size of SPPs on the weight gain of corrosion maybe greater than that on the hydrogen solubility.

Study on Microstructure of Hot Extruded N36 Zirconium Alloy Tubes

DAI Xun, LIU Hong, WANG Pengfei, WANG Ying, ZHAO Wenjin, SHI Minghua

2012, 33(S2): 43-46,78.

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Microstructure of hot extruded tube was studied by TEM,EDS and SEM equipped with EBSD.The results showed that elongated structure with some recrystallized grains and sub-grainboundaries was formed after extrusion.The second phase particles（SPPs）,distributed randomly,was confirmed as β-Zr with a small quantity of β-Nb and Zr-Fe-Nb type precipitates.

Fracture Morphology Analysis of Iodine Induced Stress Corrosion Cracking of N36 Zirconium Tube

YAN Meng, PENG Qian, ZHAO Wenjin, SHENG Zhongqi, DAI Xun

2012, 33(S2): 47-50.

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Hoop tensile test is performed on N36 zirconium tube ring specimen at 350℃ iodine gas en-vironment to study the I-SCC behavior of N36 zirconium tube under iodine action.The fracture surface after I-SCC is observed by scanning electron microscope,and the result shows that pitting is prone to take place at edge of specimen,and group of cracks propagate parallel to the fracture surface.There is no clear boundary between intergranular and transgranular crack.

Effect of Sn Content on Corrosion Resistance of Zr-Sn-Nb Alloys in Steam

YANG Zhongbo, ZHAO Wenjin, MIAO Zhi, CHEN Liang

2012, 33(S2): 51-55.

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The corrosion behaviors of Zr-xSn-1Nb-0.3Fe（x=0~1.5wt%） alloys have been investigated in the superheated steam of 400℃/10.3 MPa for 270 days.Results show that the corrosion weight distinctly de-creased with the decreasing of Sn content from 1.5wt% to 0.8wt%.However,the corrosion weight was hardly changed when the Sn content was 0 0.8wt%.The characteristics of grains and second phase particles were analyzed by optical microscope（OM） and scanning electron microscope（SEM）,respectively,and the crystal structure of oxide films formed on specimens after corrosion test were characterized by X-ray diffraction（XRD） method.The microstructural characteristics indicated that some Sn promoted the recrystallization of Zr-1Nb-0.3Fe alloy,and the area fraction of precipitates in the alloy was increased with the Sn content de-creased when all the samples were the same heat treatment condition.It was found that,the higher the fraction of the tetragonal ZrO₂ in the oxide films was,the lower the corrosion rate of specimens,and it can be con-cluded that the tetragonal ZrO₂ in the oxide films makes for the corrosion resistance.

Research on Fracture Toughness of A508-Ⅲ Steel in Transition Range

MA Na, WANG Li, CHEN Yong

2012, 33(S2): 56-60,74.

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Master curve method is developed to evaluate the elastic-plastic fracture toughness of ferritic material in transition region.It has been successfully used in RPV integrity assessment.The tensile tests of A508-Ⅲ steel in-50℃ is performed.As part of RPV aging management base data,this research focuses on the test method of KJC and T0 using Pre-Cracked Charpy V notched（PCCv） samples and 0.5 inch Compact Tensile（CT） samples.The test temperature is-50℃.Results show that,the difference of T0 between PCCv and 0.5CT is only 0.6℃.

Research on Fabrication and Tensile Properties of 9Cr-ODS Steel

CHEN Wanhua, ZHOU Zhangjian, HU Helong

2012, 33(S2): 61-64.

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The oxide dispersion strengthened（ODS） steel powders with the chemical composition of Fe-9Cr-1.5W-0.15S was prepared by mechanical alloying（MA）.The MA powders were consolidated by hot isostatic pressing（HIP） at 1150℃ under 110 MPa for 2 h.Then additional hot deformation and heat treat-ment were performed.Tensile property measurement show that the ODS steel is with high strength at tem-perature and high temperature.Additional deformation combined heat treatment can improve the plasticity obviously.

Study on Evolution of Grain Boundary Composition in Nickel Based Alloy 690

LI Hui, XIA Shuang, LIU Wenqing, PENG Jianchao, ZHOU Bangxin

2012, 33(S2): 65-69.

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The solute and impurity atoms segregation at grain boundaries before carbide precipitation in Alloy 690 were examined by atom probe tomography.The evolution of grain boundary chemistry after carbide precipitation in Alloy 690 was examined by X-Ray energy dispersive spectrum adapted at high resolution transmission electron microscopy.C,B and Si atoms segregation,C and Cr co-segregation,and Cr enrichment at grain boundaries were observed before carbide precipitation at the grain boundaries.The chromium depletion zone formed at the grain boundaries after carbide precipitation.The chromium concentration at grain boundaries decreased with the aging time prolonging.The chromium concentration at grain boundaries reaches the minimum value after aging at 715℃ for 15 h.And then,the chromium concentration at grain boundaries increased with the aging time prolonging.After the carbides were fully covering the grain boundaries,the enrichment of chromium at grain boundaries can be observed.The chromium depletion zone,especially the chromium content gradient in the chromium depletion zone was the main factor that influenced the corrosion resistance of the grain boundary in alloys with high chromium content.

Research on 310S for Microalloying with Addition of Titanium and Zirconium

PAN Qianfu, LIU Chaohong, TANG Rui, JIANG Mingzhong, YI Wei

2012, 33(S2): 70-74.

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The modified 310S stainless steels（310S+0.25wt.%Ti+0.2wt.%Zr）was manufactured by the vacuum induction melting,vacuum arc melting,forging,hot rolling,solution heat treatment and stabilizing treatment.Microstructure and tensile properties of modified 310S were respectively measured with scanning electron microscope and material testing machine.The grain size of modified 310S was about 30um,ZrC was the mostly percipitation observed on grains and grain boundaries,and the modified 310S express well intensity and plastic nature in normal and elevated temperature.Contrasted with the Japan research production of modified 310S addition with alone element Ti or Zr,the modified 310S with addition of Ti + Zr or Ti + Nb express smaller average grain size,well tensile-strength in normal and elevated temperature,the ranking of effectiveness enhanced the strength of 310S by addition element was Nb＞Ti＞Zr.

Difference between Flow Accelerated Corrosion and Erosion-Corrosion of Carbon Steel Pipes

WANG Guili, MA Na, CHEN Yong

2012, 33(S2): 75-78.

Abstract(20) PDF(9)

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This paper introduced the wall thinning research on two typical carbon steel pipes in the con-ventional island of a nuclear power plant.Operation condition analysis,chemical composition analysis,me-tallic phase analysis,micrographic examination,and XRD analysis are performed.The difference between erosion-corrosion and flow accelerated corrosion are made clear during the research.Measures to solve the wall-thinning problems of different pipes are also given in this paper.

Oxidation Mechanism of SiC Coated Layer in Air Atmosphere at 1400℃

LIU Malin, LIU Bing, SHAO Youlin, NIU Xiaoping

2012, 33(S2): 79-82,86.

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The SiC coating layer of HTGR fuel particles is the most critical layer in hindering the release of fission products.In this paper,SiC layer was prepared in a spout fluidized bed by chemical vapor deposi-tion on an industrial scale.High temperature oxidation experiments were carried out at different temperatures at 1400℃.The microstructure and composition were studied using different characterization methods,in-cluding EDS and SEM analysis.High-resolution SEM results showed that the oxidation started from the sur-face and gradually formed a punctate distribution of the oxide.The small crystal structure（^μm） of the SiC surface was very clear at the beginning and this crystal structure was oxidized at high temperatures,and disappeared gradually to form oxides of Si on the SiC surface.There was a stacking fault stress due to the different thermal expansion coefficient and elastic modulus of SiC and Si oxides,leading to the gradual formation of cracks around the punctates,and then with the increasing temperature,the crack further increased the oxidation rate of SiC,finally the formed Si oxides layer fell off from the particles.It can be seen clearly that the layer was peeling when the temperature was increased to 1400℃.But the oxidation layer was very thin（~1μm）,so the remain SiC coated layer has the same function of hindering fission products in the TRISO particles.EDS results can also validate these conclusions.

Study on Dynamic Corrosion Performance of Stainless Steel Used as Primary Pipe

HE Kun, SUN Danqi, ZHANG Hai, LIU Gang

2012, 33(S2): 83-86.

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The corrosion behavior of stainless steel used as primary pipes is simulated in the primary water media by dynamic corrosion test for 2000h,and the kinetic curve and corrosion rate of stainless steel were obtained.Compared with the corrosion rate of stainless steels made in France which is 3.70 mg/dm².m,the corrosion rates of domestic materials are 3.88 mg/dm².m in Yantai and 2.69 mg/dm².m in Shanghai.The results show that the corrosion rate of domestic and foreign materials is comparable,and the domestic stainless steel is with good corrosion resistance.Besides,the oxide film of the stainless steel is analyzed by SEM and XRD.

Study on Acceptance Standards for Surface Flaw in Austenitic Steel Piping during in-Service Inspection

CHU Qibao, YAO Lin, SUN Zaozhan, MA Jingxian

2012, 33(S2): 87-90.

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The paper gives a general introduction of formulation principles and main principal safety cri-teria of acceptance standards during in-service inspection of ASME XI.Model of circumferential and axial surface flaw in austenitic steel piping are explicated particularly.Allowable sizes of surface flaw with differ-ent aspect ratios of a/l in austenitic steel piping are deduced,and the calculation formula of allowable flaw sizes detected by nondestructive examinations during pre-service and in-service inspection considering UT inspection technical characteristics is presented.

Effect of Extrusion Process on Microstructure of B₄C/Al-Si Composites

JIAN Min, FU Daogui, WANG Meiling, LI Gang, WANG Guanchun, ZOU Congpei

2012, 33(S2): 91-96.

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B₄C/Al-Si composites were prepared by hot extrusion process with Al-Si alloy powder and B₄C powder as raw material.Effect of extrusion process on microstructure of the composites was studied.The results show that B₄C particles distribute uniformly in Al-Si matrix,and no particle agglomeration is found under experimental condition（Extrusion temperature: 350℃~500℃;mould angle: 45°,60ånd 90°;holding time: 30min~120min）.B₄C/Al-Si composites become densification when extrusion temperature reaches 450℃,with 60 min holding time.With the increasing of extrusion temperature and holding time,the number of silicon phase decreases while its particle size increases obviously.Mould angle mainly affects the integrity of B₄C particles,and B₄C particle is broken seriously since local strain enhancing with the increas-ing of mould angle.

Effect of Bi Content on Microstructure and Mechanical Properties of Lead-Free Brass Alloy

ZHOU Jun, CHEN Yong, JIANG Mingzhong, ZHANG Zhonglun, PAN Qianfu

2012, 33(S2): 97-100,106.

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Effect of Bi content on microstructure,mechanical properties and cutting property of lead-free brass alloy has been studied.Result of SEM,EDS and XRD shows that the alloy is comprised with α phase and β phase,some part of Bi exists in β phase and phase boundaries.Brinell hardness,tensile strength,yield strength and cutting property are promoting,while elongation percentage and percentage reduction of area are decreasing as content of Bi is increasing.Alloy 2# with 0.7% Bi is with appropriate mechanical properties as Pb-brasses.

Research Development of Tungsten-Based Materials Used as Plasma Facing Materials of Fusion Reactor

HUANG Bo, YANG Jijun, TANG Jun, LIU Ning, SHU Xiaoyan, MIAO Faming, TANG Rui

2012, 33(S2): 101-106.

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Plasma facing materials（PFM） has been one of the most important technological questions for fusion reactor study.Among of traditional PFM candidates（C,Be,and W）,W materials exhibits the most promising applications.However,pure W still has several drawbacks such as low re-crystallization tempera-ture,and high ductile-brittle transition temperature.Therefore,great efforts have been devoted to new W-based alloy and composite materials in recent years.In this paper,the classification and the research pro-gress of the W-based materials are reviewed.Especially,the underlying microscopic mechanisms of enhanced performance of these materials are summarized.At last,the research prospect for W-based PFM is proposed.

Effect of Water Absorption Rate on Blister Behavior of B₄C-Al Composites

WU Songling, LIU Xiaozhen

2012, 33(S2): 107-109.

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Blister test of B₄C-Al composite materials with different density were completed and the rate of water absorption was calculated.The results reveal that the difference on the rate of water absorption is significant,and the bubble occurs only when the rate of water absorption is in a specific range,which is dif-ferent with the result of EPRI.The reason of blister may be that the pressure of hydrogen produced in the cor-rosion reaction exceeds the bonding of clads and core,subsequently plastic deformation would take place and blister formed.

Synthesis Methods of Boron Carbide Powder

LI Bei, JIAN Min, WANG Meiling, FU Daogui, ZOU Congpei

2012, 33(S2): 110-113,119.

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Boron carbide is an important ceramic material,which is widely used in civil,military and nuclear industries.The boron carbide synthesis methods include direct synthesis method,carbothermal reduction,self-propagation high-temperature synthesis,mechanochemical method,chemical vapor deposition,sol-gel method and solvothermal method.In this paper the main characteristics and development of boron carbide synthesis methods are summarized.

Aging Management of Reactor Pressure Vessel for PWR Nuclear Power Plants

LUO Qiang, XU Qi, ZHAO Jisong, REN Liping, CHEN Yong, MA Na

2012, 33(S2): 114-119.

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In this paper,structure features of Western PWR pressure vessel and WWER pressure vessels was compared,the aging mechanisms were analyzed,and PDCA cycle in RPV aging management was established.According to the actual status of organizational model and management activities of PWRs in China,it explained the establishment and optimization of aging management activities,the operation and control,the check,inspection,evaluation and maintenance of Western PWR pressure vessel and WWER pressure vessels.

Adsorption Characteristics of Boron on Boron Selective Resin

WANG Meiling, WANG Guanchun, FU Daogui, JIAN Min, LIU Xiaozhen, ZOU Congpei

2012, 33(S2): 120-123.

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Research was carried on the adsorption of boron on boron selective resin.The results show that the quantum of adsorption of boron is obviously affected by the type of resin,and the turn is OH^-＞Cl^-＞SO₄^2-.For the same type resin,the adsorptive quantity of boron increases with the concentration of feed solution and decreases with the temperature rise;The isotherm of adsorption is in accordance with Freundlich isotherm equation,the adsorption belongs to favourable type and the process of adsorption is spontaneous and radiative.Particle diffusion is the key step of adsorption.

Study on Helium Leak Detection for Post-Irradiation Fuel Rods

KUANG Liuwei, REN Liang, JIANG Linzhi, GUO Chengming, YU Feiyang, YIN Chunyan

2012, 33(S2): 124-127.

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This paper introduced the helium leak detection method for post-irradiation fuel rods and helium leakage device was designed,including the pressure helium device,suction gun leak detection device and vacuum-chamber leakage device,which was proved to be effective in hot cell.In the experiment,helium leak detection of post-irradiation fuel rod was conducted by suction gun and segment helium leakage device before cutting,and the background was similar to the leakage rate,which indicated that there was no leak source on the fuel rod.During the cutting,helium was detected,which further indicated that there was no leak source.Suction gun helium leakage detection was carried out after cutting,and it indicated that the background was similar to the leakage rate and there was no leak source on the fuel rod.

Calculation of Elution Curve for Boron Isotope Separation in Column Chromatography

FU Daogui, WANG Guanchun, WANG Meiling, JIAN Min, LI Gang, LIU Xiaozhen, ZOU Congpei

2012, 33(S2): 128-131.

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Based on two fundamental assumptions of equilibration plate theory,the computation model is established,the calculation process is programmed and by inputting some essential parameters,every amount of 10B and 11B of each plate in the chromatographic column during the elution is obtained.The curves were as follows: the elution curves of boric acid and 10B isotope under the conditions of different amount of adsorption,and the 10B isotope distribution curves in the chromatographic column of different migration dis-tances during the course of multi-column cyclical separation.The computation results show that the equili-bration plate theory model can well explain qualitatively the phenomena of 10B isotope separation of column chromatography such as the plateau zone in the front of elution curve,the most enriched 10B at the rear part of the elution curve,and dependence of atomic fraction of 10B on migration length during the migration.

Failure Analysis for Wires of Coordinate Location Sensor for Control Rod in Reactors

ZHU Wei, WANG Fei, TANG Hongkui, ZHOU Yun, WEN Bang

2012, 33(S2): 132-135.

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The coordinate location sensor of control rod of XX Nuclear Power Plant failed during operation.In order to analyze the reason,it is necessary to take apart of the coordinate location sensor.Each coordinate sensor has 12 wires and each wire has a V flexure at the same position.And one wire is fractured at the top of the V flexure.In order to study the fracture reason of the wire,the microstructures of fractured,flexural and normal wires were investigated by using scanning electron microscope（SEM）,energy dispersive X ray spectrometer（EDS）,and optical microscopy（OM）.The results indicate that the wires are stress corroded,and the grain boundary became rather weak in the high temperature and high pressure environment in the reactor.Finally the wire is broken at the top of the V flexure due to tensile stress which caused by the differential heat expansion coefficient of the material.

Development Status and Prospect of Catalyst for Passive Hydrogen Combiner

ZHANG Liang, LIU Jinhong, LONG Dijun

2012, 33(S2): 136-139.

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The safety of nuclear power is the pursued aim of nuclear power development.The hydrogen would be emitted in both accident and normal state,so the danger of H2 explosion exists.The dehydrogenation system of NPP is the most important nuclear safety equipment.One of the most important parts of the system is the catalyst of H2 combiner.Currently the type of dehydrogenation catalyst is supported noble metal catalyst.Whereas,the special characteristics of nano-composite material make it be the important research direction in catalyst field.In this paper the development status of H2 combiner has been studied,and according to studying direction of catalyst area,the development suggestion has been proposed.

Research on Strain-Displacement Relationship of Tensile Test

CHEN Le, LIANG Bo, CHEN Xin, DAI Xun

2012, 33(S2): 140-143.

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This paper mainly focused on the strain-displacement relationship（ε-d） during tensile test for establishing the relationship among the force/stress,strain and displacement.Several materials were tested on MTS 810 hydraulic servo-machine,and the experimental data was analyzed.The results showed that the ε-d was a linear function during elastic stage,while it indicated nonlinear in the whole plastic stage,so it was unreliable to determine the yielding strength by the displacement method.The ε-d dependence was in good conformity with polynomial function by fitting the measured data of strain in the range of extensometer（up to 32% at RT and 16% at HT of the elongation） and the whole displacement,and the ε-d values could be obtained up to 70%（RT） or 35%（HT） of the elongation by extrapolating the above function and related data,while the maximum fitting error was no more than 3%.That is to say,as the result of overcoming the limit range of extensometer,we can perfectly get the complete engineering stress-strain（σ-ε） data.

Research on Factors Influencing Flux of NbCl₅ and Relations between Flux of NbCl₅ and Quality of Spreading Niobium

LIU Tingwei, ZHANG Liang, PAN Xiaoqiang, LI Tongye, DAI Shengping, YANG Jing

2012, 33(S2): 144-148.

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With the method of comparison,the relations among load of NbCl₅,inside temperature,purity of NbCl₅,carrying methods of argon gas and average flux of NbCl₅ were roundly studied.And the effect of flux of NbCl₅ on felting of materials,quality of spreading niobium and using rate of NbCl₅ was analyzed.The problems such as controlling difficulty of flux of NbCl₅ and felting of materials were solved.The results show that the carrier gas should not pass the inside of the vaporing pot and the heating curve should be confirmed by load of NbCl₅ and heating characteristics,for controlling the flux relatively stably.And the early flux of NbCl₅ shall be small,and then enlarges very slowly in the process of spreading niobium.The average flux is about 260 g/h.In this way,materials do not felt,and both of quality of tiny spheres and using rate of NbCl₅can be ensured.

2012 Vol. 33, No. S2