Effect of doping on microstructure and technical usage property of tantalum wire

Effect of different dopants and various dopants quantity at different annealing temperatures on microstructure of tantalum wire, bending of tantalum wire after sintering and bending after pressing into tantalum powder and sintering were investigated through observation of microstructure and testing of bending of tantalum wire after sintering and bending after pressing into tantalum powder and sintering. The results show that the recrystallization temperature of tantalum wire increases and the grain of microstructure can be reduced with the increase of dopants quantity. At the same time, the effect of dopant Ce on reduction of the grain is more obvious than that of dopant Ge. The bending time of tantalum wire after sintering increases with the increase of dopant Ge or Ce quantity. Under the same condition, the bending time of tantalum wire after pressing into tantalum powder and sintering worsens with the increase of oxygen content in tantalum powder. The bending time of tantalum wire doped with Ge and Ce after pressing into tantalum powder and sintering is better than that of tantalum wire doped with Ge, while that of tantalum wire doped with Ge is better than that of pure one when oxygen content in tantalum powder is not too high.     

Phase-field simulation of dendritic growth in a forced liquid metal flow coupling with boundary heat flux

A phase-field model with forced liquid metal flow was employed to study the effect of boundary heat flux on the dendritic structure forming of a Ni-40.8%Cu alloy with liquid flow during solidification.The effect of the flow field coupling with boundary heat extractions on the morphology change and distributions of concentration and temperature fields was analyzed and discussed.The forced liquid flow could significantly affect the dendrite morphology,concentration and temperature distributions in the solidifying microstructure.And coupling with boundary heat extraction,the solute segregation and concentration diffusion were changed with different heat flux.The morphology,concentration and temperature distributions were significantly influenced by increasing the heat extraction,which could relatively make the effect of liquid flow constrained.With increasing the initial velocity of liquid flow,the lopsided rate of the primary dendrite arm was enlarged and the transition of developing manner of the secondary arms moved to the large heat extraction direction.It was the competition between heat flux and forced liquid flow that finally determined microstructure forming during solidification.     

Influence of clay concentration on the morphology and properties of clay-epoxy nanocomposites prepared by in-situ polymerization under ultrasonication

To investigate the effect of clay concentration on the structures and properties of bisphenol-A epoxy/nanoclay composites, three composites with organoclay concentrations of 2.5wt%,5wt%,and 7.5wt% of the epoxy resin were prepared by in-situ polym- erization under mechanical stirring followed by ultrasonic treatment.The clay aggregates on micro-scale indicate the absence of fully exfoliated nanocomposites.The layer space decreases with the increase of clay concentration,which suggests that the exfoliation would be constrained if more clay is added as the ultrasonic force is exerted.The thermal decomposition temperature remains almost unchanged with the increase of clay concentration.The glass transition temperature of the composites decreases slightly with the in- crease of clay concentration,whereas the storage modulus increases with the increase of clay concentration.     

Origin of the pre-peak in the structure factor of liquid Fe-4.30C-0.21Ce alloy

The liquid structure of Fe-4.30C and Fe-4.30C-0.21Ce alloys was studied by high temperature X-ray diffractometer. The results show that for Fe-C alloy the nearest neighbor distance of the eutectic alloy is 0.259-0.260 nm at the temperature range of 1200-1400℃, which increases to 0.269-0.271 nm with the addition of 0.21% (mass fraction) Ce in the Fe-C alloy at the same temperature range. There is a pre-peak at Q = 15.5 nm-1 on the original intensity curve and structure factor S(Q) of the liquid Fe-4.30C-0.21Ce alloy, which was caused by the Ce atoms in the C-Ce clusters. Combined with the shared face, the tetragonal structure can meet the requirement for the distance of Ce-Ce atoms. It also shows that the cluster size in the liquid Fe-4.30C-0.21Ce alloy increases with the decreasing temperature.     

Solute redistribution and micromechanical properties of rapidly solidified multicomponent Ni-based alloys

The solute trapping effect and microhardness enhancement of quaternary Ni-5%Cu-5%Ag-5%Sn and quinary Ni-5%Cu-5%Ag-5%Sn-5%Ge alloys during rapid dendritic solidification are investigated by glass fluxing technique. In these two alloys, the experimental maximum undercoolings of 310 K(0.18 T_L) and 220 K(0.13 T_L) have been achieved and the rapidly solidified microstructures are composed of α(Ni) and(Ag) solid solution phases. The morphological transition from coarse dendrite into equiaxed structure is observed for α(Ni) phase with the increase of undercooling. The dendritic growth velocity of α(Ni) phase in quaternary Ni-5%Cu-5%Ag-5%Sn alloy is larger than that in quinary Ni-5%Cu-5%Ag-5%Sn-5%Ge alloy, which increases firstly and then decreases with the enhancement of bulk undercooling. The Vickers hardness of α(Ni) phase in these two alloys is enhanced with the increase of undercooling, which is attributed mainly to the grain refinement effect. Meanwhile, the solute trapping effect of Cu, Sn and Ge elements in the α(Ni) phase also contributes to the microhardness enhancement under large undercoolings. The addition of Ge element effectively increases the microhardness of α(Ni) phase due to solute strengthening mechanism.     

Microsegregation and Rayleigh number variation during the solidification of superalloy Inconel 718

The microstructure and composition of the residual liquid at different temperatures were investigated by scanning electron microscopy （SEM） and energy dispersive X-ray spectrometer （EDX） associated with the Thermo-calc software calculation of the equilibrium phase diagrams of Inconel 718 and segregated liquid. The liquid density difference and Rayleigh number variation during solidification were estimated as well. It is found that the heavy segregation of Nb in liquid prompts the precipitation of δ and Laves phase directly from liquid and the resultant quenched liquid microstructure consists of pro-eutectic γ＋eutectic,or complete eutectic according to the content of Nb from low to high. The liquid density increases with decreasing temperature during the solidification of Inconel 718 and the liquid density difference is positive. The largest relative Rayleigh number occurs at 1320°C when the liquid fraction is about 40vol%.     

Microstructures and Thermal Properties of Sn–Bi–Zn–Ga Alloys as Heat Transfer and Heat Storage Materials

Low melting point alloy is a potential high-temperature heat transfer medium because of the high thermal conductivity, low solidus temperature and wide range of use temperature. Consequently, we investigated the possibility of using Sn–Bi–Zn–Ga alloys as heat storage and heat transfer material. Moreover, we investigated the microstructure and phase compositions by electron probe micro-analysis(EPMA) and X-ray diffusion(XRD). Results show that the new structures and phases are formed in the alloy matrix with Ga additions, which lead to the improvement of the thermal properties. An extensive thermophysical characterization of the Sn–Bi–Zn–Ga alloys has been performed by differential scanning calorimeter(DSC) analysis. The addition of Ga lowers the peak temperature and increases the heat capacity of the alloys. The thermal expansion of the test alloys increases with increasing temperature and the densities decreases with Ga additions. As the density, specific heat capacity and thermal diffusivity change with temperature and physical state, the thermal conductivity of the alloys first decreases and then increases. These results demonstrate the feasibility of using Sn–Bi–Zn–Ga alloys as the high-temperature heat transfer fluid.     

Influence of ZrO2 on sintering and crystallization of CaO-Al2O3-SiO2 glass-ceramics

ZrO2 was added into CaO-Al2O3-SiO2 glass-ceramics and the effect of ZrO2 on sintering and crystallization of CaO-Al2O3-SiO2 glass ceramics was investigated. The results show that the sintering shrinkage ratio of glass particles decreases with the increase of the content of ZrO2. ZrO2 has an unfavourable effect on sintering shrinkage ratio of glass particles. The sintering shrinkage ratio of glass particles increases with the increase of sintering temperature. The increase of sintering temperature favors the decrease of the liquid phase viscosity of glass particles. ZrO2 has little effect on crystallization of main crystalline phase （β-wollastonite）. However, it promotes the crystallization at relatively low temperature.     

Uniaxial tension and tensile creep behaviors of EPS

The mechanical behavior of EPS(Expanded polystyrene) with three densities at room temperature and under tension loading was studied.The results show that EPS material is characterized by brittle behavior in the tension tests,and tensile properties of EPS increase with the increase of density.Volume fraction has no a significant effect on the modulus of these foams.The tensile creep strain increases with stress for EPS with same density,indicating that the creep behavior is of the stress dependency.And the creep behavior of EPS exhibits density dependency,which the creep strain decreases with densities for a fixed stress value.Moreover the creep behavior under the constant tension load is well in coincidence with the three-parameter solid model.     

Influence of elemental iron on hydrogen content in superheated aluminum-iron melts

The hydrogen content in liquid binary aluminum alloys with 1,3,5 and 8 wt% iron has been determined in the temperature range from 973K to 1103K. The hydrogen content in molten Al-Fe alloys increases remarkably when the temperature of the meh rises to about 1053K. This work indicates that the alloying element iron plays an important role in hydrogen content in snperheated Al-Fe alloy melts below about 1053K. The results make it clear that the hydrogen content in the mekt ahuminum reduces with the increasing element levels. A conclusion is drawn that the degree of gassing in molten AL-Fe alloys is hound up with the properties of oxide film of aluminum alloy melts. The element iron has no effect on the compact stntcture of oxide film in aluminum melts. The effects of alloying element are theoretically analyced in terms of Wagner interaction parameter. According to the values of the first order interaction parameter, it is concluded that the interaction between iron atom and aluminum is much stronger than that between hydrogen atom and ahanintum, and the addition of the alloying element decreases the affinity of liquid aluminum for hydrogen.     

Measurement and Analysis of Density of Molten Ni-W Alloys

1IntroductionNi-based heat-resistant superalloys are widely usedto make critical components in gas-turbine engines,suchas bladeetc.But they are very hard and difficult to bemachined,the net-shape machining of these materials isveryimportant.Computer simul…     

Relation between doping and texture and property of tantalum bar and wire

Relation between doping and texture and property of tantalum bar and wire was carefully investigated by optical microscope, SEM fractograph, electron microprobe analysis, density test, observation of TEM and mechanical property test at room temperature. It is illustrated that the grain of tantalum bar after sintering reduces with the increasing of dopant quantity, and the effect of dopant Ce on reduction of the grain is more obvious than that of dopant Ge, even that sintering is becoming insufficient and the density of tantalum bar tends to be lower with the increaseing of dopant Ce. The recrystallization temperature of tantalum wire increases and the grain of texture reduces with the increaseing of dopants quantity. The tensile strength of tantalum wire at room temperature increases with the increasing of dopants quantity, while its elongation decreases with the increase of dopant Ge quantity and rises with theincrease of dopant Ce quantity. And the strengthening effect of dopant Ce is clearer than that of dopant Ge.     

Electrodeposition of Ni-Cr alloy on aluminum substrate

1 INTRODUCTIONOwing to low mass , high strength and easymachining, aluminum ( Al) and its alloys havebeen widely appliedin many fields .But the chemi-cal character of Al is very active ,it can be oxidizedeasilyinthe at mosphere and erodedinthe foul con-dition,and its wear resistance is poor . All theseseriously affect its application andlifeti me .It is aneffective protective measure to i mprove perform-ance by means of plating alloy on Al substrate .Ni-Cr alloys have many characteristi…     

Fe-Si-B-Nb-Cu-Zr非晶（纳米晶）合金的磁性机理研究

采用单辊甩带法制取了Fe-Si-B-Nb-Cu-Zr非晶合金薄带。利用X射线衍射仪（XRD）、差示扫描量热法（DSC）和振动样品磁强计（VSM）等手段对非晶态和晶化后的薄带的微观结构和磁性能进行了表征和测试,研究了Fe-Si-B-Nb-Cu-Zr合金中磁性能随着Zr含量以及退火温度变化的磁性机理。结果表明,在铸态Fe-Si-B-Nb-Cu-Zr非晶合金中,饱和磁感应强度Bs随Zr含量的增加而减小,矫顽力Hc随Zr含量的增加而增大。经过退火处理后的Fe-Si-B-Nb-Cu-Zr合金的饱和磁感应强度变化不大,但矫顽力随着退火温度的升高先减小后增高,矫顽力在510℃退火时达到最小值,但随着温度增加矫顽力进一步增大。在510℃退火时纳米晶粒与非晶相之间的体积比达到最佳,有效各向异性〈K〉最小,软磁性能最好。     

Effects of HIPing pressure on microstructures and properties of TiAl alloy

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超声场作用下胡萝卜渗透脱水质量传递规律研究

以胡萝卜为原料,探讨了在超声场作用下,浸泡液浓度、渗透时间、温度等因素对胡萝卜—蔗糖溶液固液体系传质速率的影响.通过实验得出了胡萝卜失水率及固形物得率,由此确定了不同条件下胡萝卜失水率及固形物得率常数,基于质量守恒定律建立了胡萝卜渗透脱水传质模型.结果表明:当温度保持不变时,物料的失水率及固形物得率常数随蔗糖溶液浓度的增加而增加,同时温度对高浓度渗透液的影响比低浓度的大;当渗透液浓度不变时,随着反应温度增加失水率常数增加,固形物得率常数降低.失水率随时间变化与可渗出但仍保留在物料中的含水率呈正比线性关系.     

液柱冲击塔湿法烟气脱硫的试验研究

设计了一种新型的液柱冲击塔脱硫装置，通过冷态试验研究各种结构和运行参数的变化对液柱冲击塔脱硫效率的影响。研究结果表明，在试验范围内，液柱冲击塔的脱硫效率随着喷液密度、塔内风速、液气比、循环水池pH值、烟气入口温度的增大而提高，随着SO2入口质量浓度的增大而降低。减小液柱冲击塔阻挡层的通流截面或阻挡层与液柱喷嘴之间的距离可以有效改善脱硫浆液的雾化效果，从而显著提高脱硫效率。选择适当的结构和运行参数，液柱冲击塔的脱硫效率可以达到95%以上。     

环境条件对离心式喷嘴雾化性能的影响

以离心式压力雾化喷嘴为研究对象，对不同环境条件下喷嘴雾化特性的影响进行了数值模拟研究，获得了不同环境压力和环境温度对油膜厚度和雾化锥角等雾化特性参数的影响规律。利用FLUENT软件，在喷油压力4.0 MPa、燃油温度100 ℃的条件下，对环境压力由0.1 MPa升至3.0 MPa、环境温度由-50 ℃升至400 ℃过程中的燃油雾化特性进行了数值计算。结果表明，当环境压力一定时，环境温度增加，气体密度减小，燃油蒸发作用加剧，气相燃油比例增大，雾化效果增强；当环境温度一定时，环境压力增加，气体密度增大，油膜厚度增大，液相燃油比例增大，不利于燃油雾化。     

用高低温熔体混合法制备Al- 18%Si合金

采用熔体混合法将不同温度的纯铝熔体与600 ℃半固态Al-36%Si合金熔体混合制备Al-18%Si合金,研究纯铝液温度、保温温度和保温时间对Al-18%Si合金初生硅相显微组织及力学性能的影响。实验结果表明:熔体混合法可制得初生硅为颗粒状且均匀分布的Al-18%Si合金;在一定范围内,初生硅的粒径随熔体温差的增大而减小,随保温时间的延长呈先减小后长大的趋势;900 ℃的铝液与600 ℃半固态Al-36%Si合金熔体混合后于750 ℃保温20 min获得的Al-18%Si合金力学性能最好,初生硅平均粒径最小。