The Mechanism of the Formation and Transformation of Ettringite

The formation and transformation of ettringite were studied by measuring the ion concentration in liquid phase and analyzing the composition in solid phase. The effects of C3A, gypsum lime and C-S-H gel on ettringite formation and transformation were also investigated. The experimental results shuw, that, when gypsum was presented in solid phase, the composition of liquid phase was in favor of ettringite formation. Ettringite formation consisted of three reactions including the formation of [ Al （OH）6 ]^3- octahedral, formation of Ca-Al polyhedra prism in which Ca and Al polyhedra arranged alternately, as well as entrance of SO4^2- into the channel of polyhedra. [ Al （OH）6 ]^3- formation, which was the slowest reaction, controlled ettringite formation. The concentration of AlO2^- was a main factor that influenced ettringite formation. After gypsum in solid phase was consumed, [ SO4^2- ] decreased quickly and [ AlO2^- ] increased, and it was possible that ettringite transformed into hydrated monsulfate calcium aluminate （ be called M in short） in thermodymanics. The rate of transformation was controlled by diffusion of AlO2^- .     

Effect of P/M value on the preforms and microstructures of spray formed 70Si30Al alloy

A novel 70Si30Al alloy was prepared by the spray forming process for electronic packaging materials. The effect of the ratio of atomization pressure to metal melt mass flux rate （P/M） on the preforms and microstructures of the spray-deposited 70Si30Al alloy was studied. The results indicate that the PIM value has a considerable influence on the formation of the preforms and the optimal value is in the range of 0.209-0.231 MPa/（kg.min^-1）. The microstructure of the spray formed 70Si30AI alloy is fine and homogenous. The primary silicon phases distributing in the aluminum matrix evenly are fine and irregular. The aluminum matrix is divided into two groups： supersaturated α-Al phase or α-Al phase and Al-Si pseudoeutectic phase or Al-Si eutectic phase.     

Effect of annealing on the microstructure and mechanical properties of Mg-2.5Zn-0.5Y alloy

The microstructure and mechanical properties of extruded Mg-2.5Zn-0.5Y alloy before and after annealing treatments were investigated. The as-extruded alloy exhibits a yield tensile strength （YTS） of 305.9 MPa and an ultimate tensile strength （UTS） of 354.8 MPa, whereas the elongation is only 4%. After annealing, the YTS and UTS decrease to 150 MPa and 240 MPa, respectively, and the elongation increases to 28%. Interestingly, the annealed alloy maintains an acceptable stress level even after a much higher ductility is achieved. These excellent mechanical properties stem from the combined effects of fine α-Mg dynamic recrystallization （DRX） grains and a homogeneously distributed icosahedral quasicrystalline phase （I-phase） in the α-Mg DRX grains. In particular, the superior ductility originates from the coherent interface of I-phase and α-Mg and from the formation of the secondary twin {101 1}-{101 2}（38°〈1 2 10〉） in the tension twin {1012}.     

Model of small-scale self-focusing and spatial noise in high power laser driver

A linearization model was used to analyze the laser beam propagation in a high power laser driver and the influence of the small-scale self-focusing and spatial phase noise on beam quality in disk amplifiers. The quantitative relations between intensities of spatial phase noise, B-integral, and beam intensity contrast in near field are given explicitly. A spectrum specification of phase noise has been obtained by setting a limit to the contrast of an output beam.     

Characteristics and evolution of ore-forming fluids of the Chongjiang copper deposit in the Gangdise porphyry copper belt, Tibet

Petrography, microthermometry, and scanning electron microscope/energy dispersive spectrometer （SEM/EDS） studies were performed on the fluid inclusions in the ore-beating quartz veins and quartz phenocrysts in the porphyry of the Chongjiang porphyry copper deposit. The analyses of the fluid inclusions indicate that the ore-forming fluids were exsolved from magma. They are near-saturated, supercritical, rich in volatile constituents, and have the capture temperature of 362-389℃ and salinities of 17.7wt%- 18.9wt% NaC1 eq. With the decreasing of temperature and pressure, the supercritical fluids were separated into a low salinity vapor phase and a high salinity liquid phase. During quartz-sericitization, the high salinity fluid boiled and separated into a low salinity vapor phase and a high salinity liquid phase. The high salinity inclusions that formed in the boiling process had daughter mineral melting temperatures higher than the homogenization temperatures of the vapor and liquid phases. The late fluids that are responsible for argillization are of lower temperature and salinity.     

Microscopic phase-field simulation of the coarsening behavior of coherent precipitates in Ni-Al alloys

On the basis of the microscopic phase-field dynamic model and the microelasticity theory, the characteristics of the coarsening behavior of γ＇ phase in Ni-Al alloys have been systematically studied in a certain volume fraction of the precipitates. It was found that the initial irregular shape, randomly distributed γ＇ phase, gradually transformed into cuboidal shape, regularly aligned along the [100] and [010] directions, and a highly preferential selected microstructure was formed during the later stage of precipitation. The volume fraction of the precipitates produced some effects on the precipitate morphology but did not produce an obvious effect on the regularities of precipitate distribution. The coarsening rate constant from the cubic growth law decreased as a function of volume fraction for small volume fractions, remained constant for intermediate volume fractions, and increased as a function of volume fraction for large volume fractions. During the coherent coarsening process, four ＂splitting＂ patterns between γ＇ phases, which belonged to different antiphase domains, were produced via particle aggregation, such as an L-shaped pattern, a doublet, a triplet, and a quartet.     

Effect of Li content on the microstructure and properties of lead-free piezoelectric （K0.5Na0.5）1-xLixNbO3 ceramics prepared by SPS

Lead-free piezoelectric （K0.5sNa0.5）1-xLixNbO3 （x = 0at%-20at%） ceramics were synthesized by spark plasma sintering （SPS） at low temperature and the effects of LiNbO3 addition on its crystal structure and properties were also studied. When the Li content was less than 6at%, a single proveskite phase with the similar structure of （K0.5Na0.5）NbO3 was formed; and a secondary phase with K3Li2Nb5O15 structure was observed in the 6at% 〈 x 〈 20at% compositional range. Furthermore, LiNbO3 existed as the third phase when the Li content was higher than 8at%. The grain sizes increased from 200-500 nm to 5-8 μm when the K3Li2Nb5O15 and LiNbO3 like phases were formed. With increasing Li content, the relative density of the ceramics first decreased from 97% to 93% and then kept constant. The piezoelectric coefficient d33, dielectric constant, and planner electromechanical coupling factor exhibited a decreasing tendency with increasing Li content because of the decrease in density and the formation of the secondary phase such as K3Li2Nb5O15 and LiNbO3. The formation of dense microstructure with a single phase is necessary in improving the properties of the （K0.5Na0.5）1-xLixNbO3 ceramics.     

Determination of the solvation film thickness of dispersed particles with the method of Einstein viscosity equation

The dispersion of a solid particle in a liquid may lead to the formation of solvation film on the particle surface, which can strongly increase the repulsive force between particles and thus strongly affect the stability of dispersions. The solvation film thickness, which varies with the variation of the property of suspension particles and solutions, is one of the most important parameters of the solvation film, and is also one of the most difficult parameters that can be measured accurately. In this paper, a method, based on the Einstein viscosity equation of dispersions, for determining the solvation film thickness of particles is developed. This method was tested on two kinds of silica spherical powders （namely M1 and M2） dispersed in ethyl alcohol, in water, and in a water-ethyl alcohol mixture （1：1 by volume） through measuring the relative viscosity of dispersions of the particles as a function of the volume fraction of the dry particles in the dispersion, and of the specific surface area and the density of the particles. The calculated solvation film thicknesses on M1 are 7.48, 18.65 and 23.74 nm in alcohol, water and the water-ethyl alcohol mixture, 12.41, 12.71 and 13.13 nm on M2 in alcohol, water and the water-ethyl alcohol mixture, respectively.     

Phase and Rietveld Refinement of Pyroehlore Gd_2Zr_2O_7 Used for Immobilization of Pu （Ⅳ）

The phase of pyrochlore Gd_2Zr_2O_7 used for immobilization of Pu （Ⅳ） was investigated, tetravalent cerium was used as the simulacrum for plutonium with tetravalence, and the compounds in the system Gd_2Zr_2-_xCe_xO_7 （0.0≤x≤2.0） were synthesized via a high temperature solid reaction method with Gd_2O_3 and ZrO_2 powders being used as the starting materials. Based on the collected XRD data of the gained samples, the phase and microstructural change of compounds were calculated by means of rietveld structural refinement method. The experimental results indicated that the phases of compounds were changed from pyrochlore to fluorite-type phase with the increasing x. The linear relation between a and x was discovered in the range of fluorite-type phase, which accorded with a = 0.52748 ＋ 0.00825 x （0.2≤x≤2.0）, while V= 0.14668 ＋ 0.00711 x （0.2≤x≤2.0） was also achieved.     

Phase and Rietveld Refinement of Pyrochlore Gd_2Zr_2O_7 Used for Immobilization of Pu(Ⅳ)

The phase of pyrochlore Gd2Zr2O7 used for immobilization of Pu(Ⅳ) was investigated, tetravalent cerium was used as the simulacrum for plutonium with tetravalence, and the compounds in the system Gd2Zr2-x Ce x O7(0.0 x 2.0) were synthesized via a high temperature solid reaction method with Gd2O3 and ZrO2 powders being used as the starting materials. Based on the collected XRD data of the gained samples, the phase and microstructural change of compounds were calculated by means of rietveld structural refinement method. The experimental results indicated that the phases of compounds were changed from pyrochlore to fluorite-type phase with the increasing x. The linear relation between a and x was discovered in the range of fluorite-type phase, which accorded with a = 0.52748 + 0.00825 x(0.2 x 2.0), while V = 0.14668 + 0.00711 x(0.2 x 2.0) was also achieved.     

非真空熔铸铍铜合金大规格铸锭的研究

在非真空熔铸铍铜合金大规格铸锭时,需要长时间的熔化和保温.由于铍在金属熔体中的氧化烧损量达到0.004 4%/min以上,熔体中的铍质量分数处于不断下降的状态,因而不同铸锭之间、同一铸锭头尾w（Be）偏差达到6%以上;铍及铍铜原料的大量烧损容易导致铸锭夹杂,进而影响铸锭的综合成品率;同时,由于铍具有强烈的脱氧作用,熔体极易吸气,铸锭内部容易出现气孔等铸造缺陷.通过上百炉次的试验,对熔铸工艺的每个细节深入研究和试验,确定了合理的熔铸工艺,在生产铍铜合金大规格铸锭时,铍及铍铜材料的烧损率分别降到6%及3%以下,铸锭化学成分偏差≤4%,铸锭综合成品率达到80%以上.     

Microstructure and tensile behavior of hot extruded AZ91 alloys at room temperature

AZ91 alloys were prepared by hot extrusion and its microstructure and tensile behavior at room temperature were investigated.Compared to as-cast ingot,the grain size of hot-extruded material is more refined,the intermetallic phase Mg17Al12 is broken and dispersed discontinuously.Both strenth and elongation of AZ91 are improved by hot extrusion.Tensile behavior and fracture surface of the experimental material were studied.Due to the change in microstructure,the fracture mechanism of extruded material is different from that of as-cast ingot,the latter is mainly a brittle fracture,Ductile fracture plays a role in hot-extruded AZ91 failure at room temperature.     

电磁水平连铸1560镍基合金的组织与性能研究

为提高1560镍基合金圆形铸锭的质量,采用电磁水平连铸方法对其进行生产实验,并对圆锭及其坯料再进一步轧制和冷拉所生产系列棒线材产品的组织与性能进行了研究。结果表明,该方法生产的1560镍基合金电磁铸锭的芯部由中心等轴晶组成,其溶质元素偏析程度明显降低,且常规水平连铸过程中常见的芯部裂纹、缩孔和疏松等缺陷也得到有效消除。该方法不仅取消了传统工艺中的铸坯退火、锻造及打磨等工序,而且还缩短了工艺流程,其产品成材率也由传统工艺时的70％提升到90％以上。     

铸铁激光表面改性的组织与性能特征的研究

论述了激光表面熔融处理后硬化层的显微组织与性能特征，讨论了组织对硬度分布的影响试验结果表明：经激光表面熔融处理后，球墨铸铁熔化层组织为先共晶奥氏体（快冷后转变为Ｍ＋ＡＲ）＋莱氏体，相变层组织为马氏体＋残余奥氏体＋球状石墨；灰口铸铁的熔化层组织为细小树枝（Ｍ＋ＡＲ）＋弥散分布的树枝间层片状变态莱氏体（Ｍ＋ＡＲ＋Ｆｅ３Ｃ）的变态亚共晶白口组织，相变层组织为马氏体＋残余奥氏体＋片状石墨在相变区，球状石墨周围的组织较复杂，靠近熔化层处的石墨球周围出现双壳层组织，由一层马氏体＋残余奥氏体包围，再围以莱氏体或先共晶奥氏体＋莱氏体组织     

Microstructural evolution of TiAl base alloy during three-stepped thermo-mechanical treatment

ＴｉＡｌｂａｓｅａｌｌｏｙｓｈａｖｅｂｅｉｎｇｃｏｎｓｉｄｅｒｅｄａｓｐｒｏｍｉｓｉｎｇｈｉｇｈｔｅｍｐｅｒａｔｕｒｅｓｔｒｕｃｔｕｒａｌｍａｔｅｒｉａｌｓ.Ｂｅｉｎｇｓｔｕｄｉｅｄｆｏｒｎｅａｒｌｙ 2 0ｙｅａｒｓ,ｔｈｅｆｕｎｄａｍｅｎｔａｌｏｆＴｉＡｌｂａｓｅａｌｌｏｙｓｈａｖｅｂｅｅｎｕｎｄｅｒｓｔｏｏｄ(ｍｏｒｅｃｌｅａｒｌｙ) ,ａｎｄｔｈｅｉｒｍｅｃｈａｎｉｃａｌｐｒｏｐｅｒｔｉｅｓ ,ｅｓｐｅ ｃｉａｌｌｙｔｈｅｒｏｏｍｔｅｍｐｅｒａｔｕｒｅｄｕｃｔｉｌｉｔｙ ,ｈａｖｅｂｅｅｎｇｒｅａｔｌ…     

高效多晶铸锭的热场优化及其工艺改进

针对ECM PV450炉型高效铸锭工艺电池转换效率偏低问题进行研究及实验,通过优化热场结构使侧部加热器与坩埚底部籽晶相对位置的变化,在纵向上提升侧部加热器高度、在横向上添加保温材料,使籽晶尽可能与加高温隔离;同时改进化料工艺适当增加顶部温度、降低侧部和底部熔化温度,在设备和工艺两方面最大限度的保护坩埚底部籽晶不被高温熔化,保证硅锭籽晶的完整性,消除了硅锭边角区域的效率短板,平均电池转换效率由18.33%提升至18.48%,大幅度提高了铸锭品质.     

16MnCr5钢锭表层凝固及冷却过程中组织转变规律研究

对１６ｎＣｒ５钢锭表层凝固及冷却过程中的组织转变规律进行了分析,结果表明,钢锭表层我晶转变的不完全性对随后的组织转变有显著的影响,并形成了不均匀铁组织分布。     

过热度对Ti-47Al-2Cr-2Nb缩孔缩松的影响研究

使用CaO坩埚真空感应熔炼的方法对Ti-47Al-2Cr-2Nb进行铸锭,然后通过改变过热度,从宏观和微观两方面对钛铝合金铸锭中缩孔缩松的位置及含量分别进行分析,经过大量实验,最终得出过热度对Ti-47Al-2Cr-2Nb铸锭缩孔缩松的影响规律。     

A new approach for preparing SiC particle-reinforced aluminum matrix composites by applying electromagnetic field

A new method for preparing SiC particle-reinforced aluminum matrix composites was introduced. In order to improve the ingot surface and homogeneity of structure, low frequency electromagnetic field was applied during the direct chilling casting process. The experimental results show that the new method can be used to prepare SiC particle-reinforced aluminum matrix composites; under the effects of the low frequency electromagnetic field, the microstructure of ingot is refined and the distribution of SiC particles is improved.     

电渣重熔宏微观多尺度数值研究进展

电渣重熔过程伴随着电磁、流动、传质和传热等一系列复杂的宏观传输现象,同时伴随金属熔体形核和生长等一系列微观现象,宏微观现象之间彼此相互影响、相互制约,决定着最终重熔铸锭质量。在过去几十年里,研究者已经建立了电磁场、流场、温度场和溶质场宏观传输数学模型,揭示了电渣重熔体系内电流强度、磁感强度、焦耳热、电磁力、温度和溶质元素分布,以及渣金两相流动。最近,研究者建立了电渣重熔铸锭凝固微观组织数学模型,揭示了电渣重熔过程铸锭凝固组织演变规律和金属熔池形貌,以及重熔工艺对铸锭凝固组织的影响规律。然而,要全面揭示电渣重熔过程复杂的宏微观传输现象,还需要在电渣重熔过程熔渣内带电离子迁徙行为、电化学反应、枝晶间溶质扩散与流动、铸锭凝固收缩等方面进一步深入研究。