用激光拉曼谱表征半导陶瓷湿度传感器中晶粒微结构的特性

半导陶瓷湿度传感器是用固相反应和粉末压片烧结的方法制作，它以二氧化锆、二氧化硅、五氧化二磷为主料，并且掺杂三氧化二钇和五氧化二铌．借助于高分辨率的四角和单斜二氧化锆的激光拉曼标准谱，二氧化锆晶粒的微结构显然在未掺杂和用三氧化二钇或五氧化二铌掺杂的样品中分别属于单斜和四角对称晶系．它们在激光显微镜下发出可以区分的不同色彩的荧光．未掺杂的二氧化锆晶粒是线度为１～２μｍ的斜角四边形，而掺杂烧结的晶粒是尺寸大到３～１０μｍ的正方形。

纳米板钛矿基二氧化钛中的晶格畸变

借助精确的Ｘ射线衍射测量，结合独立衍射峰对不同晶粒度纳米板钛矿基二氧化钛样品中板钛矿和金红石相的微结构参量进行了较细致的研究，给出了标明物相、晶面指数（ｈｋｌ）和晶面间距ｄｈｋｌ值详细分析结果的系列ＸＲＤ谱，并得到了晶面间距、晶格常数、轴比、晶胞体积等参数数值及其相对常规粗晶的变化情况，从而初步揭示出其晶粒微结构的尺寸效应。首次发现。

Effects of microwave sintering temperature and soaking time on microstructure of WC-8Co

WC-8Co cemented carbide samples were processed via microwave irradiation in a 2.45 GHz, high-power multi-mode microwave cavity. The densification of the compacts and the microstructures of the prepared alloys were studied. The results demonstrate that the liquid phase is formed around 1300 ℃ and nearly full densification is obtained at 1450 ℃ for 5 min via microwave irradiation. The microstructures of microwave sintered samples have finer and more uniform WC grains than those of vacuum sintered samples. Besides, the WC grain size and distribution are only decided by the sintering temperature. Holding time has negligible effects on them. No matter how holding time is, the mean grain size is 2.7 pan when the sintering temperature is kept at 1450 ℃.

Properties of magneto-rheological fluids based on amorphous micro-particles

To improve the magneto-rheological (MR) properties of magneto-rheological fluids, self-made amorphous alloy particles, the composition of which was Fe76Cr2Mo2Sn2P10B2C2Si4, were used as the disperse phase to replace traditional carbonyl iron (CI) particles to prepare amorphous based magneto-rheological fluid (AMRF). Soft magnetic properties and densities of the amorphous particles and the CI particles were tested and compared. The results indicate the amorphous particles present a lower density but larger magnetization intensity and larger permeability at lower field levels. Properties of the AMRF with 20% particles in volume fraction were tested and compared with the CI based MR fluid (CMRF). The AMRF presents a saturation yield stress of 41 kPa at ~227 kA/m and a sedimentation ratio of 80%. The results indicate the magneto-rheological fluid based on amorphous micro-particles has better MR properties and sedimentation stability than that based on CI particles at lower field levels (0-200 kA/m).

先进制造领域推广技术(续)

9R2k5型宽频高磁导率铁氧体制备技术1）技术开发单位电子科技集团第九研究所2）技术简介采用组合加杂技术，解决高磁导率的难题，通过工艺试验完善配方及工艺。重点研究原材料化学和物理特性对材料磁导率μi值的影响，确定材料最佳主配方；优化最佳掺杂及含量，以改善材料晶粒微结构及材料高频宽带频谱特性，使材料具有高饱和度磁感应强度和高电阻率，能在宽频下承受较大功率；同时引入超微粉加工技术，自主开发了材料的制粉无水工艺，改善了材料性能，在宽频带范围内获得较低的损耗，更好地满足现代通信器件的要求。

Microstructure formation and grain refinement of Mg-based alloys by electromagnetic vibration technique

The microstructure formation and grains refinement of two Mg-based alloys,i.e.AZ31 and AZ91D,were reported using an electromagnetic vibration(EMV) technique.These two alloys were solidified at various vibration frequencies and the microstructures were observed.The average size of grains was quantitatively measured as a function of vibration frequencies. Moreover,the grain size distribution was outlined versus number fraction.A novel model was proposed to account for the microstructure formation and grain refinement when considering the significant difference of the electrical resistivity properties of the solid and the liquid during EMV processing in the semisolid state.The remarkable difference originates uncoupled movement between the mobile solid and the sluggish liquid,which can activate melt flow.The microstructure evolution can be well explained when the fluid flow intensity versus vibration frequency is taken into account.Moreover,the influence of the static magnetic field on texture formation is also considered,which plays an important role at higher vibration frequencies.

Influence of electromagnetic stirring on microstructure of AZ91-0.8%Ce magnesium alloy

Effect of electromagnetic stirring on microstructure of AZ91-0.8%Ce magnesium alloy was investigated. The results show that electromagnetic stirring causes a change of morphology of α-Mg phase from coarse dendrites to fine rosette-like or spherical shape. Grain size is significantly refined within the range of input voltage 75?125 V, moreover, the optimum input voltage corresponded to the minimum value (64 μm) of grain size is 125 V. Compared to the non-stirred condition, the amount of β-Mg17Al12 precipitate under the stirred condition obviously increases. The grain refinement of AZ91-0.8%Ce alloy is mainly attributed to multiplication of existing grains in the melt caused by forced fluid flow under electromagnetic stirring condition. Addition of 0.8% Ce results in the formation of ‘necking’ at secondary dendrite arm roots of α-Mg crystals, and consequently, it is helpful to increase the number of heterogeneous nucleation.

Grain refinement and plastic formability of Mg-14Li-1Al alloy

Al-5Ti-1B master alloy was added into Mg-14Li-1Al(LA141)alloy and then LA141 sheets were prepared by extrusion and cold rolling.The effect of the addition level of Al-5Ti-1B master alloy on the grain size of LA141 alloy was investigated as well as the effects of the total reduction of cold rolling and the annealing temperature on microstructure,mechanical properties and plastic formability of the LA141 sheets.The results show that the optimal addition level of Al-5Ti-1B master alloy into LA141 alloy is 1.25%(mass fraction)and LA141 alloy has the finest grains.With the increase of the total reduction of cold rolling,the grains of the as-rolled LA141 sheets were flattened gradually.A proper anneal temperature of 200℃ is obtained for the cold rolled LA141 sheets. Under this condition,microstructure of the LA141 sheets consists of fine and uniform equiaxed grains and has higher Erichsen cupping index(IE).

Influence of minor Sc additions on grain refinement and microstructure characteristics of a high Zn-containing Al-Zn-Mg-Cu-Zr alloy

In the present work, scandium elements with a series of contents(0.06 wt.%, 0.10 wt.%, 0.14 wt.%,0.17 wt.%, 0.20 wt.% and 0.25 wt.%) were added in a high Zn-containing Al-Zn-Mg-Cu-Zr alloy and the corresponding as-cast microstructure characteristics including grains and phases were thoroughly investigated. The results indicated that fine grain boundaries existed in these alloys and fine MgZn2phases discontinuously distributed on them. Besides,AlZnMgCu eutectic phases and Sc, Zr-containing phases with flocculent morphology were observed. As scandium contents vary from 0.06 wt.% to 0.17 wt.%, the average grain size continuously decreased and its equiaxial characteristics were strengthened. Meanwhile, the content of AlZnMgCu eutectic phase showed a decrease trend. When scandium contents were 0.20 wt.% and 0.25 wt.%, no further enhancement on grain refinement was observed, so as to the reduction of AlZnMgCu eutectic phase content. Besides, Sc, Zr-containing phases with blocky morphology were observed and the alloy with a scandium content of 0.25 wt.% possessed a larger amount of blocky Sc, Zr-containing phase than the alloy with a scandium content of 0.20 wt.%. Grain refinement and reduction of AlZnMgCu eutectic phase content associated with scandium addition were discussed.

Microstructure and mechanical properties of TA15/TC11 graded structural material by wire arc additive manufacturing process

A graded structural material(GSM)with a material transition from TA15 to TC11 was fabricated by wire arc additive manufacturing(WAAM)method.The grain morphology,chemical composition,microstructure and mechanical properties of the as-deposited GSM were all characterized to investigate their variations along the deposition direction.The results indicate that from TA15 to TC11,the grain size decreases and a transition from columnar grains to equiaxed grains occurs.The content of alloy element alters greatly within a short distance,and the width of the mutation zone is 800μm.Both TA15 and TC11 regions exhibit basketweave microstructure withα-phase andβ-phase.However,during the transition from TA15 to TC11,theα-lath becomes fine,which leads to an increase in microhardness.The tensile test shows that the bonding strength at the interface is higher than the longitudinal strength of TA15,and the lateral elongation at the interface is higher than that of TA15 and TC11.

Corrosion properties of plastically deformed AZ80 magnesium alloy

AZ80 magnesium alloys were deformed at 200,250,300,350 and 400℃ with different deformation degree of 50%,75%, 83%,87%and 90%,respectively.The corrosion properties of different deformed AZ80 samples were studied by galvanic test in 3.5%NaCl solution.The results show that plastic deformation could improve the corrosion resistance of AZ80 alloy;and the corrosion rate of AZ80 deformed at 250℃ with the deformation degree of 83%was the lowest,which was 33%of the as-cast AZ80 alloy.Further studies of the microstructure show that the refined grain size and continuously distribution ofβphase around the grain boundary did have a positive effect on the improvement of corrosion resistance of AZ80 alloys.For AZ80 alloys,the smaller the grain size is,the more homogeneous the structure is,and the better the corrosion resistance is.

Synthesis of Ni-Zn ferrite and its microstructure and magnetic properties

Nanometer Ni0.5Zn0.5Fe2O4 powders with spinel phase were prepared by the hydrothermal method using purified FeSO4 solution from sodium jarosite＇s slag as materials. The results show that the spinel phase of Ni0.5Zn0.5Fe2O4 powders begins to form at a relatively low temperature （130 ℃） and a shorter holding time （1 h） when pH=8. The crystallization kinetics equation at 200℃ is ln[-ln（1-x）] =-0.78＋0.951n t. The growth activation energy of Ni0.5Zn0.5Fe2O4 grains is 41.6 kJ/moL in hydrothermal synthesis process. With the increase of sintering temperature, the density and diameter shrinkage of ferrite circulus increase, whereas its pores decrease. The results of magnetic measurements show that saturation magnetic flux density Bs increases and the coercivity Hc decreases with the increase of their sintering temperature. Magnetic parameters of all the investigated samples satisfy the character demand of high Bs, low Br and low Hc of soft magnetic ferrite materials.

Microstructure and tensile properties of AM50A magnesium alloy prepared by recrystallisation and partial melting process

Prior to thixoextrusion, the microstructural evolution of semi-solid AM50A magnesium alloy prepared by the recrystallisation and partial remelting (RAP) route was investigated.The effect of compressive ratio on microstructure of semi-solid AM50A magnesium alloy was studied.Furthermore, tensile properties of thixoextruded components were determined.The results showed that the occurrence of recrystallised grains was closely associated with the location of the first liquid formed above the solidus.With prolonging holding time, deformed microstructure was penetrated, causing fragmentation, which resulted in the decrease of average grain size.Moreover, prolonging holding time was favorable for the improvement of the degree of spheroidization due to the increase in the amount of liquid.With the increase in compressive ratio, the size of solid grain decreased, the degree of spheroidization was improved during partial remelting, and the tensile properties of thixoextruded AM50A components were improved.The tensile properties for AM50A magnesium alloy thixoextruded from starting material produced by the RAP route were better than those of the same alloy produced by die-casting and thixomolding.

Effects of RE and Sr additions on dendrite growth and phase precipitation in AZ91D magnesium alloy

To develop AZ91D alloys with fine microstructure, effects of the addition of rare earth (RE), Sr and RE + Sr on the dendrite growth and phase precipitation in AZ91D magnesium alloy were studied, respectively. The results show that the microstructure is refined and the morphology of β-Mg17A112 phase is modified with RE or Sr addition, especially with the RE+Sr composite addition which can reduce the average grain size of AZ91D alloy obviously to 141 μm. The needle-like or block-like new phases adhering to β-Mg17A112 phase form at interdendrites during solidification. The enrichment of RE or/and Sr elements in front of the solidification interface, especially at the tips of α-Mg dendrite, which restricts the growth of α-Mg dendrite, changes the preferential growth of α-Mg and finally results in the grain refinement and the blunting of α-Mg dendrite.

Self-assembled flower-like microstructure in Zn_(1-x)Cd_xO nanoparticles

The structural and optical characterization of cadmium-doped zinc oxide nanoparticles synthesized by precipitation method was studied.X-ray diffraction study confirmed the substitution of cadmium dopant without disturbing the basic wurtzite structure of zinc oxide.The average crystalline size,lattice constants and unit cell volume also increased up to4%of cadmium doping.Energy gaps of the samples were determined from the ultraviolet?visible absorption spectrum as well as Tauc’s plot which infers that the energy gap decreases with the increase of cadmium content.Fourier transformation infrared spectrum confirms the cadmium dopant through peak shifting from485to563cm?1.Photoluminescence spectrum also defines the cadmium dopant by intensity increase.The broad Raman peak at437cm?1indicates that the wurtzite structure of zinc oxide is weakened by5%cadmium doping.Field emission scanning electron microscope study also confirms the existence of particles in nanometer size and it indentifies the microstructure transformation from nanoparticles to jasmine flower-like structure on5%cadmium doping.

Morphological and Optical Characterizations of CaAl2O4 Doped with Trivalent Praseodymium

This work was synthesized CaAl2O4 （calcium aluminate） doped with trivalent praseodymium ions. CaAl2O4 with praseodymium 1.0% and 0.5% were synthesized. The powders of aluminates were characterized by scanning electron microscopy and luminescence spectrofluorimetry.CaAl2O4, praseodymium ions, luminescence doped with praseodymium ion that showed less porosity in its grain structure and luminescent transitions that are dependent on the wavelengths of excitation and showing both types of transitions both 5d-4f and 4f-4f.

690合金与152合金焊接热影响区微观组织研究

应用电子背散射衍射(EBSD)、扫描电镜(SEM)和显微硬度仪研究了压水堆(PWR)压力容器(RPV)控制棒驱动机构(CRDM)管嘴690合金与152合金焊接热影响区上部、中部和根部的残余应变分布、显微硬度、晶粒平均取向差(GAM)、晶粒边界显微结构和金相特征。研究结果表明:残余应变从上部到下部逐渐减少,最大残余应变5.15%,位于最后焊接的上部热影响区;重合位置点阵∑3边界平均分数从上部到下部逐渐增加,最小∑3边界平均分数是46.6%,显著低于基体金属的68%。因此认为,最后焊接的上部热影响区具有最高应力腐蚀破裂(SCC)敏感性。

Preparation of sound ribbons with submicrometer-grained microstructure on a Mg–Zn alloy

In this paper, a viable way to fabricate Mg alloy sound ribbons with ultra-fine-grained microstructure was presented. The hot-rolled and annealed Mg-0.4Zn （at%） alloy exhibited excellent rollability to form sound ribbons with submicrometer grains when subjected to one-pass cold rolling process. The more balanced multi-mode dislocation slips originated from the significant decrease of critical resolved shear stress for non-basal slip with the addition of solute Zn and the favorable crystallographic orientation were suggested to be responsible for the excellent cold rollability. The formation of ultra-fine-grained microstructure was attributed to low-temperature dynamic recrystallization occurring during the cold rolling process with large strain.

Grain oriented growth and properties of ultra-high temperature CaBi_2Nb_2O_9 piezoelectric ceramics

CaBi2Nb2O9 (CBNO) ceramics was prepared at 1050℃ using regular flake-like CBNO powders as the precursor, and synthe-sized by the molten salts synthesis method. The tropism degree and microstructure of the ceramics were analyzed, and the die-lectric, ferroelectric and piezoelectric properties were characterized. Compared with conventional methods, the properties of CBNO ceramics by the new preparation method were found to be better. As the sinter temperature decreases, the grain growth becomes regular with textured features. The polarization process becomes easy to be realized at room temperature. Moreover, the dielectric loss decreases and the piezoelectric constant increases significantly.

Three dimensional microstructures and wear resistance of Al-Bi immiscible alloys with different grain refiners

The three dimensional(3D) microstructures of Al-Bi alloys with different grain refiners(Al-5Ti-B, Al-3B and Al-3Ti) have been studied using synchrotron X-ray microtomography. The relationships between the microstructures and the corresponding wear behavior are verified through the friction and wear tests. The worn surfaces of the samples with grain refiners tested under 15 and 60 N loads are analyzed using Scanning Electron Microscopy(SEM). The results indicate that the addition of grain refiners is beneficial to the size and distribution of the Bi-rich particles in Al-Bi alloys. Compared with Al-5Ti-B and Al-3B grain refiners, the Bi-rich particles are more uniformly distributed and spherical with finer size with the addition of Al-3Ti grain refiner. The refinement renders the Al-20wt%Bi alloy refined by Al-3Ti the superior wear resistance with respect to those refined by Al-5Ti-B and Al-3B grain refiners, corresponding to the microstructures with fine and uniformly distributed Bi-rich particles in the Al matrix.