Electromagnetic Filtration of Primary Fe-Rich Phases from Al-Si Alloy Melt

Electromagnetic filtration of primary Fe-rich phases (complex compound of AlFeSiMn) from Al-Si alloy melt containing 1.2 wt pct Fe have been studied by theoretical analysis and on a self-designed electromagnetic filtration equipment. The principle of the electromagnetic filtration is that the EMF (electromagnetic force) scarcely acts on the primary Fe-rich phases having low electric conductivity, which are then moved in the direction opposite to that of the EMF. Experimental results show that the primary Fe-rich phases are separated from Al-Si alloy melt and are collected in the filter while the melt is in horizontal flow. The removal efficiency of the primary iron-phases (77) calculated is less as the greatest flow velocity of the melt (UM) and the height of the filter (2h) are larger, while it becomes larger as EMF, operating distance of electromagnetic force (cr) and particle size (dv) become larger. It has been confirmed that the primary iron-phases larger than 20 jim can be removed efficiently by theoretical analysis and experiments. This new technique is high efficient and available for continuously flowing melts as compared with natural settling and filtration methods, which offer a possibility for recycling high quality aluminum alloys.

Primary phase evolution of rheo-processed ADC12 aluminum alloy

The primary phase evolution of ADC12 aluminum alloy rheo-processed by mechanical rotational barrel system was studied by differential scanning calorimetry（DSC）, optical microscopy（OM） and scanning electron microscopy（SEM）. The semisolid slurry analyses show that the solid fraction of ADC12 aluminum alloy increases from 0.38 to 0.43 while the roundness decreases from 0.45 to 0.38 with increasing the rotational speed from 30 to 120 r/min. When the pouring temperature decreases from 620 to 580 °C, the primary α（Al） morphology changes from spheroidal to rosette-like. Besides, the average particle size of primary phase and solid fraction increase with the decrease of pouring temperature. By rheo-diecasting process, the components with fine, spherical and uniformly distributed primary α（Al） particles were obtained, and the best microstructure was contained at the pouring temperature ranging from 595 to 605 °C. The rheo-processing feasibility of ADC12 aluminum alloy can be explained by the grains controlled growth theory, and the semisolid slurry obeys the Mullins-Sekerka criterion when solidifying in the high pressure die casting machine.

Phases of Environmental Evolution Indicated by Primary Chemical Elements and Paleontological Records in the Upper Pleistocene-Holocene Series for the Salawusu River Valley,China

Studies of lithology, sedimentary facies and the distribution regularity of SiO2 and Al2O3 contents and Al2O3/SiO2 ratio allow us to divide the Upper Pleistocene-Holocene Series represented by the MUanggouwan section in China＇s Salawnsu River valley into six segments： MGS1, MGS2, MGS3, MGS4, MGS5 and MGS6. The boundary ages for MGS1 （the Dishaogouwan and Dagouwan Formations）, MGS2 （the upper Chengchuan Formation）, MGS3 （the middle Chengchuan Formation）, MGS4 （the lower Chengchuan Formation）, MGS5 （most strata of the Salawusu Formation） and MGS6 （the bottom of the Salawusu Formation and the top of the Lishi Formation） correspond to those of MIS1, MIS2, MIS3, MIS4, MISS and MIS6, respectively, from deep sea sediments or continental glaciers. MGS5 can be subdivided into five subsegments （MGS5a, MGS5b, MGS5c, MGS5d and MGS5e） and the boundary ages of these subsegments correspond to those of MISSa, MISSb, MIS5c, MIS5d and MIS5e, respectively. Based on the paleoenvironment and paleoecology indicated by the primary chemical elements, fossil vertebrates, mollusks and pollen grains, we hypothesize that MGS1, MGS2, MGS3, MGS4, MGS5 and MGS6 and the subsegments of MGS5 match the corresponding stages for oxygen isotopes in the deep sea sediments and continental glaciers, and the substages of MIS5 in terms of climatic characters, further explaining the phenomena that determined the formation of the late Quaternary strata and the paleontology of the Salawusu River valley. These phenomena relate to fluctuations in the global climate （and particularly in the East Asian monsoon） during the glacial and interglacial periods.

Influence of high pressure and manganese addition on Fe-rich phases and mechanical properties of hypereutectic Al-Si alloy with rheo-squeeze casting

The influence of high pressure and manganese addition on Fe-rich phases(FRPs)and mechanical properties of Al-14Si-2Fe alloy with rheo-squeeze casting(RSC)was investigated.The semi-solid alloy melt was treated by ultrasonic vibration(UV)firstly,and then formed by squeeze casting(SC).Results show that the FRPs in as-cast SC alloys are composed of coarseβ-Al5(Fe,Mn)Si,δ-Al4(Fe,Mn)Si2 and bone-shapedα-Al15(Fe,Mn)3Si2 phases when the pressure is 0 MPa.With RSC process,the FRPs are first refined by UV,and then the solidification under pressure further causes the grains to become smaller.The peritectic transformation occurs during the formation ofαphase.For the alloy with the same composition,the ultimate tensile strength(UTS)of RSC sample is higher than that of the SC sample.With the same forming process,the UTS of Al-14Si-2Fe-0.8Mn alloy is higher than that of Al-14Si-2Fe-0.4Mn alloy.

Research on fractal characteristics of primary phase morphology in semi-solid A356 alloy

Semi-solid slurry of A356 alloy was prepared by low superheat pouring and slightly electromagnetic stirring, and the fractal characteristics of morphology in semi-solid primary phase was researched. The fractal dimensions of primary phase morphology in the semi-solid A356 alloy were calculated by the program written to calculate the fractal dimensions of box-counting in the image of solid phase morphology in semi-solid metal slurry. The results indicated that the morphology of primary phase in semi-solid A356 prepared by low superheat pouring and slightly electromagnetic stirring is characterized by fractal dimension, and the primary phase morphology obtained by the different processing parameters has different fractal dimensions. The morphology of primary phase at the different position of ingot has different fractal dimensions, which reflected the effect of solidified conditions at different positions in the same ingot on the morphology of semi-solid primary phase. Solidification of semi-solid alloy is a course of change in fractal dimension.

Characterization on morphology evolution of primary phase in semisolid A356 under slightly electromagnetic stirring

The effects of slight electromagnetic stirring on morphology of primary phase in semisolid A356 prepared by low superheat pouring and slight electromagnetic stirring were researched,and some characteristic parameters characterized the morphology and grain size of the primary phase were calculated.The results indicate that the stirring power has an important effect on the morphology and the grain size.The characteristics of the morphology could be characterized by the fractal dimensions and the shape factors.The fractal dimension and the shape factor change when the morphology changes with processing conditions.Both increase with the increase of the stirring power,but the fractal dimension is still affected by the grain size.The increase of stirring power could obviously improve the grain size,fractal dimension and shape factor of the primary phase.

Effects of high-pressure rheo-squeeze casting on the Fe-rich phases and mechanical properties of Al-17Si-(1,1.5)Fe alloys

The effects of high pressure rheo-squeeze casting(HPRC) on the Fe-rich phases(FRPs) and mechanical properties of Al-17 Si-(1,1.5)Fe alloys were investigated. The alloy melts were first treated by ultrasonic vibration(UV) and then formed by high-pressure squeeze casting(HPSC). The FRPs in the as-cast HPSC Al-17 Si-1 Fe alloys only contained a long, needle-shaped β-Al5 Fe Si phase at 0 MPa. In addition to the β-Al5 Fe Si phase, the HPSC Al-17 Si-1.5 Fe alloy also contained the plate-shaped δ-Al4 Fe Si2 phase. A fine, block-shaped δ-Al4 Fe Si2 phase was formed in the Al-17 Si-1 Fe alloy treated by UV. The size of FRPs decreased with increasing pressure. After UV treatment, solidification under pressure led to further refinement of the FRPs. Considering alloy samples of the same composition, the ultimate tensile strength(UTS) of the HPRC samples was higher than that of the HPSC samples, and the UTS increased with increasing pressure. The UTS of the Al-17 Si-1 Fe alloy formed by HPSC exceeded that of the Al-17 Si-1.5 Fe alloy formed in the same manner under the same pressure. Conversely, the UTS of the Al-17 Si-1 Fe alloy formed by HPRC decreased to a value lower than that of the Al-17 Si-1.5 Fe alloy formed in the same manner.

Effect of Cr content and cooling rate on the primary phase of Al-2.5Mn alloy

The effect of Cr content and cooling rate on the microstructure of Al-Mn alloy was studied using well resistance furnace melting,and the alloy was analyzed using scanning electron microscopy(SEM)and X-ray diffraction(XRD).The experimental results showed that adding Cr could significantly improve the morphology of the primary phase in the Al-2.5Mn alloy.Without Cr,the primary phase in the alloy was thick,needle-like,and strip-like structure.After adding 0.2wt%-0.5wt%Cr,the primary phase in the upper part of the alloy was gradually fined and reached the best effect at 0.35wt%Cr.When the content of Cr was 0.5wt%,the microstructure of the primary phase in the upper part began to coarsen.The bottom of the alloy was a large bulk phase,but still much finer than that without adding Cr.XRD and SEM analysis showed that the precipitation phase at the bottom was mainly Al85Mn7Cr8,while the fine microstructure at the top was Al6Mn and Al3Mn.The results of the cooling rate experiments showed that the primary phase of Al-2.5Mn-0.35Cr was further refined,and the eutectic microstructure was partly achieved,under air-cooling condition.And when the cooling method was iron die-cooling,the microstructure of the Al-2.5Mn-0.35Cr alloy was changed into a eutectic microstructure.

Electromagnetic separation of primary iron-rich phases from aluminum-silicon melt

The difference of conductivity between primary iron-rich phases and aluminum melt has been used to separate them by electromagnetic force (EMF) which is induced by imposing a direct electric current and a steady magnetic field in molten Al-Si alloy. Theoretical analysis and experiments on self-designed electromagnetic separation indicates that primary needle-like β phases are difficult to separate; while primary α iron-rich phases can be separated by electromagnetic separation. Primary iron-rich phases have been removed from the melt successfully when the molten metal flows horizontally through separation channel. The iron content is reduced from 1.13% to 0.41%.

ON THE PRIMARY η-PHASE IN A HIGH-Ti Ni-Fe-Cr BASED SUPERALLOY

The precipitation and dissolution together with their control of the primary η-phase in a high-Ti Ni-Fe-Cr base superalloy have been investigated.The precipitation of primary η-phase was found to be closely related to Ti or Al content and solidification rate of the alloy. The aggregation of blocky η-phase may remarkably reduce the tensile strength,ductility and rupture life of the alloy.The temperature-time relation of dissolution of the primary η-phase obeys T=1370-86.1 lgt for as-cast superalloy.The formation of primary η-phase may be prevented by the reasonable control of Ti or Al content and smelting process.The adoption of treatment under large hot deformation and homogenization may be the remedy for unfavorable influence of η-phase.

Computer simulation on primary α-phase of Al-7%Si solidification structure

Finite difference method was used to calculate the macroscopic transportation phenomena(including temperature and concentration fields) of Al 7%Si(mass fraction) alloy. On the basis of the results,coupled with local area magnification, the nucleation and growth of primary α phase of Al 7%Si were simulated. Relating the growth process of α phase of Al 7%Si alloy in space with structures of a sample section, the morphology and precipitating process of primary α phase of Al 7%Si alloy was simulated. The results are in good agreement with those obtained experimentally.

Chemical composition and structural identification of primary carbides in as-cast H13 steel

The aim of this study was to characterize the primary carbides formed in as-cast H13 steel. The composition, morphology, type, and size of primary carbides in as-cast H13 steel were investigated by optical microscope (OM), field emission scanning electron microscopy (FE-SEM), electron back-scattered diffraction (EBSD), and X-ray diffraction (XRD) analysis. The number of primary carbides was investigated by ASPEX automated inclusion analysis system. The results indicated that primary carbides in as-cast H13 steel are mainly composed of Cr, Mo, V, and Ti, and there exist four kinds of primary carbides in the interdendritic zones of H13 steel, which are stripy Mo–Cr-rich M2C, eutectic Mo–Cr-rich M2C, V-rich MC, and V-rich MC with Ti and N. Thermodynamic calculation indicated that M2C precipitates in liquid phase at solid fractions larger than 0.99, while MC precipitates in liquid phase at solid fractions larger than 0.96. Statistical results indicated that the number of M2C is much greater than the number of other kinds of primary carbides. Most primary carbides are blocky, with lengths of no more than 10 μm and a length/width ratio of no more than 3. The large primary carbides in as-cast H13 steel are mainly M2C.

Discussion of RE Inclusions as Heterogeneous Nuclei of Primary Austenite in Hardfacing Metals of Medium-High Carbon Steels

As the substrate for nucleation of primary austenite in hardfacing metals, the effectiveness of RE inclusions and the most common inclusions such as Al2O3, SiO2 and MnO in hardfacing metals of medium-high carbon steels was analyzed and calculated in detail. The calculation based on the theory of planar lattice misfit shows that Ce2O3, La2O3 and Ce2O2S, instead of SiO2, Al2O3, MnO and CeS, are effective as the heterogeneous nuclei of primary austenite in medium-high carbon steels.

Phase Morphology Evolution in AISI301 Austenite Stainless Steel under Different Cooling Rates

Quenching experiments were performed at different cooling rates under non-directional solidification by differential thermal analysis, and the morphologic variation of primary phase, phase transition temperature and hardness change at the same quenching temperature were investigated. The experimental results show that, with the gradual decrease of the cooling rate from 25 K/min, the morphology of ferrite starts to transform experiencing the dendrite, radial pattern, Widmanstatten-like and wire-net. Sample starts to present the Widmanstatten-like microstructure at 10 K/min which does not exist at higher or lower cooling rates, and this microstructure is detrimental to the mechanical property. Except 10 K/min, the hardness decreases with decreasing cooling rate.

Simulation Studying Effects of Multiple Primary Aberrations on Donut-shaped Gaussian Beam

In this paper, we demonstrate the variation of donut-shaped depletion pattern which influenced by multiple primary aberrations. The simulation is base on a common stimulation emission of depletion (STED) system composed by Gaussian laser and vortex phase plate. The simulation results are helpful guidelines for analyzing the aberration of depletion patterns in real situations.

Cu含量和热处理工艺对Al-Si-Mg-Mn-xCu铸造铝合金显微组织和力学性能的影响

采用三维X射线显微镜、光学显微镜、扫描电子显微镜、透射电子显微镜及硬度测试系统研究Cu含量及热处理工艺对真空压铸Al-Si-Mg-Mn-xCu合金显微组织和力学性能的影响。研究发现,虽然Cu含量增加会提高铸锭中气孔的密度和尺寸,但是Cu添加将促进凝固过程中含Cu初生相(Q-Al_(5)Cu_(2)Mg_(8)Si_(6)和θ-Al_(2)Cu)的形成,从而提高合金性能。合金中形成5种不同结构的初生相,包括共晶Si、α-Al(Fe,Mn)Si、β-Mg_(2)Si、Q-Al_(5)Cu_(2)Mg_(8)Si_(6)和θ-Al_(2)Cu相。随着Cu含量增加,θ相的面积分数迅速增加,α-Al(Fe,Mn)Si相面积分数首先降低,随后缓慢增加,而Q相的变化趋势与α-Al(Fe,Mn)Si相相反。这些初生相在热处理过程中会出现不同的演变规律。在随后的时效处理过程中,Q'和θ'相的协同析出能显著提高合金的时效硬化潜力。

四川某铜矿选冶渣综合理化特性及环境污染特性评价

针对铜矿选冶渣组成复杂、环境特性不清和治理修复难度大等问题,采用矿物解离分析仪(MLA)、X射线光电子能谱仪(XPS)和同步热分析仪-傅里叶变换红外气相色谱质谱联用仪(STA-FTIR-GCMS)等分析测试仪器研究铜矿选冶渣的综合理化特性;运用毒性浸出程序(TCLP)、改进的三步提取(BCR)、风险评估编码(RAC)和次生相与原生相比值(RSP)等方法研究铜矿选冶渣的环境污染特性.结果表明,铜矿选冶渣多呈团聚状,体积平均粒径为54.18μm,主要含铁橄榄石(75.33%)、磁铁矿(12.15%)、黑云母等物相.硫酸硝酸法测得的铜矿选冶渣Cr、Cu、Zn和Pb浓度未超过《危险废物鉴别标准浸出毒性鉴别》规定的危废限值,该铜矿选冶渣为一类一般工业固体废物.RAC法和RSP法评价结果表明,Cu是铜矿选冶渣的主要防治对象,Fe、Zn、Pb是铜矿选冶渣的次要防治对象.研究结果为铜矿选冶渣的安全处理和处置提供了基础数据.

基于幅相复平面的空管雷达测高方法研究

针对两坐标体制的空管一次雷达对目标高度测量需求,提出了一种基于幅相复平面的空管一次雷达测高方法.利用高低双波束幅相差构建复平面,在复平面-仰角形成的复空间内形成拟合曲线,通过待测样本的高低波束幅相差值在三维拟合曲线进行插值,从而得到目标仰角,进而结合目标距离获得目标高度.实录数据统计分析表明,相比传统的比相测角方法,该方法在对低仰角和低信噪比目标的仰角测量精度上具有明显优势.

变频相位干涉电场刺激对运动皮层兴奋性及运动学习表现的影响

目的:探究变频相位干涉电场刺激(temporal interference electrical fields stimulation,TI)对健康成年人运动皮层兴奋性及运动学习能力的影响,为TI刺激的应用提供依据。方法:采用随机交叉双盲设计,研究对象为健康成年人。试验1:20例受试者完成经颅磁刺激(transcranial magnetic stimulation,TMS)测试,评估刺激前后皮层兴奋性指标的改变,包括运动诱发电位(motor evoked potential,MEP)、静息运动阈值(resting motor threshold,RMT)、短时距皮层内抑制(short-interval intracortical inhibition,SICI)、皮质内促通(intracortical facilitation,ICF)。试验2:16例受试者完成随机反应时任务(random reaction time task,RRTT)和序列反应时任务(serial reaction time task,SRTT),测试指标包括平均反应时(reaction time,RT)、第一内隐学习(first implicit learning,FIL)、第二内隐学习(second implicit learning,SIL)。通过双因素重复测量方差分析评价TI刺激对受试者运动皮层兴奋性及运动学习能力的影响。结果:试验1:刺激条件和时间对MEP(F=28.787,P<0.001,ηP^(2)=0.602)和RMT(F=23.524,P<0.001,ηP^(2)=0.580)具有显著交互作用,而SICI和ICF无显著交互效应。试验2:与假刺激相比,TI刺激后SRTT中的FIL有显著提升(F=4.601,P=0.049,ηP^(2)=0.235),而RRTT任务则无显著交互效应。结论:变频TI刺激可以显著增加初级运动皮层的兴奋性,这种调控效应可能有助于促进健康成年人运动学习表现。

基于五运六气分析POAG患者的先天运气禀赋特点

目的 探析原发性开角型青光眼(POAG)患者的先天运气学禀赋特点。方法纳入2023年1月—2023年6月中国中医科学院眼科医院诊治的POAG患者226例,将其出生日期(年、月、日)转化为干支纪年后,录入Excel表,建立数据库,数据可视化采用GraphPad9.0绘制相关表格。结果 (1)天干、岁运分布:不同天干年份POAG患者,以壬年出生人数最多,共34例(15.04%),其次为乙年和己年,均为24例(10.62%);不同岁运的POAG患者,以木运年出生人数最多,共56例(24.78%),其次为土运年47例(20.80%),金运年45例(19.91%)。(2)主气、客气分布:不同主气的POAG患者,以阳明燥金时段最多,共47例(20.80%),其次为少阳相火45例(19.91%),太阳寒水42例(18.58%);不同客气的POAG患者,以厥阴风木时段最多,共54例(23.89%),其次为太阴湿土43例(19.03%),太阳寒水41例(18.14%)。(3)司天之气-在泉之气分布:以太阳寒水-太阴湿土为最多,共44例(19.47%),其次为太阴湿土-太阳寒水43例(19.03%),阳明燥金-少阴君火41例(18.14%)。(4)运气相合分布:以不和之年(含天刑年、小逆年及不和年)为最高,共95例(42.04%),其次为顺化年53例(23.45%),天符类年份(含天符年、同天符年、太医天符年)51例(22.57%)。结论 POAG患者的运气学禀赋以木为主要特点,在体合肝脏,临诊当以疏肝气,解郁滞,明目窍为要。