预浸料工艺制备氧化铝纤维增强氧化铝陶瓷基复合材料

氧化物/氧化物陶瓷基复合材料的增强体和基体均由氧化物构成,不存在氧化问题,是长寿命高可靠性构件的理想选材,可在1000~1300℃的高温环镜中可长期使用。本文借鉴树脂基复合材料单向纤维湿法预浸料制备工艺,通过配置氧化铝粉体料浆在缠绕式湿法预浸机上制备了单向氧化铝纤维预浸料,然后预浸料经铺层模压和高温热处理获得了氧化铝纤维增强氧化铝陶瓷基复合材料,同时对复合材料性能进行了表征。结果表明,氧化铝粉体料浆的固含量在50vol%,料浆溶剂中水和丙三醇的比例为3:1,纤维的走丝速度为6m/min,滚筒平行进度为0.5mm时可获得无缝隙,无纤维重叠、表面平整光滑的预浸料。通过预浸料铺层热压成型制备的复合材料拉伸强度高达208.2MPa,弯曲强度为386.7MPa。和料浆涂刷二维纤维布工艺相比,力学性能大幅度提高,且预浸料工艺具有易存储、操作简单、适于工业化生产等优势。     

Metastable alumina formation during oxidation of FeCrAl and its suppression by surface treatments

The influence of various surface treatments of industrial FeCrAl grades was investigated in order to reduce the formation of transition aluminas during thermal oxidation in the 800–950°C temperature range. High temperature gas phase annealing in H₂‐H₂O mixtures promoted the initial formation of an alpha thin film and no transition alumina formed during subsequent oxidation at lower temperatures, showing very low weight gains compared to non‐treated grades. Such a treatment was shown to be efficient for isothermal oxidation in oxygen of laboratory foil specimens but also for cyclic air exposure of fiber mats in near‐real operating conditions. Surface modification by application of a slurry TiO₂ coating before oxidation was also shown to greatly reduce the amount of transition alumina, observed by X‐Ray Diffraction and Laser Induced Optical Spectroscopy. For both treatments, the optimal conditions were determined and the influence on oxidation rate was assessed.     

An analysis of the powdered metal compaction process in solid cylind cal parts

In this study, the friction effect on the powdered metal compaction process has been analyzed by applying finite element methods. A plasticity theory applicable to powdered metal compaction is summarized and a variational form for finite element analysis is described. The compaction processes of the axisymmetric solid cylinder are simulated for different compact geometries in single-action pressing. Efforts are focused on the pressure transmitted between the upper and lower punches through the compact and density distributions within the compacts. The numerical results show that: (1) the friction condition between the metal powder and the dies can be determined simply from the force data transmitted by a single such action compaction test and the simulation results; (2) the density variations within the compacts rely on such compact geometry as the height to diameter ratio and the frictional conditions between powder and dies; the (3) additional useful information obtained includes the Min/Max density ratio within the compacts.     

离心铸造下微尺度充型流动的相似物理模拟(英文)

利用获得的相似准则,采用相似物理模拟方法,研究离心铸造过程中液态金属在微尺度空间内的充型流动规律。结果表明:在微尺度条件下,模拟流体优先充填横截面积最大的流道,当转速提高到964 r/min时,才会同时充填0.1 mm的微流道;在充型流动过程中,流体总能量保持不变,流体的自由液面是以转轴为圆心的规则圆弧面;充型速度随时间的增加而增大,迅速达到一个极值,然后随着时间的增加,变化逐渐趋于平缓,同时随着转速的增加充型速度达到峰值的时间也会极剧缩短。     

碱法高纯氧化铝微粉的制备

以氧化铝生产过程的中间物料铝酸钠溶液为原料，依据钡盐高度净化铝酸钠溶液的原理，经过脱硅、除铁净化、种分分解、焙烧后酸洗除钠等过程，最终得到纯度达99.99％，粒度90％小于2μm高纯氧化铝微粉。     

基于ANSYS的组合结构金刚石圆锯片基体离心力效应的分析

提出一种切割幅面宽度达到其直径2/3的组合结构金刚石圆锯片基体.利用有限元软件ANSYS对φ1800mm的组合结构金刚石圆锯片进行了变形和应力分析,分析总结出了组合结构金刚石圆锯片在仅受离心力、锯切力、离心力和锯切力共同作用下的变形和应力分布的特点、规律和相互影响关系.通过正交表设置不同的加工工艺参数,经过多次有限元分析计算得出组合结构金刚石圆锯片二种最优参数组合:进给速度200 cm/min、线速度30 m/s时,切割深度2～2.5 cm为好;线速度30 m/s、切削深度1 cm时,进给速度500 cm/min为好.     

真空氯化亚铝歧化法从氧化铝中提取铝

研究了以氧化铝和石墨为原料真空氯化亚铝歧化法提取铝的条件,包括反应温度、预反应和冷凝器的结构。结果表明：在1643~1843 K的温度范围内,氧化铝与碳的反应程度随着反应温度的升高而提高,但铝的提取率首先随着反应温度的升高而提高,在1743 K时达到最高,继续升高反应温度,铝的提取率反而降低;氧化铝与碳进行预反应可以提高金属铝的提取率;金属铝与CO的接触面积越小、冷凝温度越低,C、Al4C3和Al2O3杂质的含量越低,这取决于冷凝器的结构。     

应用选矿-拜耳法工艺处理一水硬铝石型中低品位铝土矿生产氧化铝的工业实践

论述选矿拜耳法生产氧化铝的工艺过程,对技术指标进行分析,总结生产实践得失,为选矿拜耳法新技术的普遍应用,优化过程指标,提高经济效苴提供借鉴。着重讨论了铝土矿选矿过程、选精矿溶出过程、赤泥沉降过程以及浮选药剂对生产的影响和改进。本文指出,应用选矿拜耳法可以经济地处理一水硬铝石型铝土矿,其生产流程简单．技术先进可靠,对低品位一水硬铝石型铝土矿资源经济有效地利用有开创性贡献。值得推广。     

湿法冶金结合喷雾干燥-热解工艺纯化和控制钨颗粒

钨因其独特的物理化学性能而被广泛的应用于半导体和高温材料。本文依次采用离子交换、溶剂萃取、重结晶、喷雾干燥和煅烧还原的方法对钨酸铵进行处理,成功制备出高纯、分散性好的微米级球形钨粉。其中,利用湿法冶金去除原料中的杂质金属,喷雾干燥和煅烧还原过程控制最终钨粉形貌结构和粒径分布。本文研究了喷雾干燥过程中溶液浓度对雾化粉末形貌的影响规律,并揭示了雾化粉末分解还原过程中的机理。该方法制备出的钨粉纯度高于99.995wt%,平均尺寸约为1.5um。本研究中的湿法冶金和粉末技术可用于合成其他具有高性能要求的金属粉末。     

Heat treatment process of bimetallic clad chromium cast iron by pipe made of carbon steel Q235/high centrifugal casting

采用离心浇铸制备外层为碳钢Q235,内层为高铬铸铁的双金属复合管。在不同温度（950、980℃）及不同冷却方式（空冷、水冷、风冷）下对复合管进行热处理试验。结果表明,试验温度下,空冷、水冷、风冷方式都可消除Q235钢铸态组织中的魏氏组织;水冷可提高复合管的硬度,但复合管出现严重畸变甚至开裂。合理的热处理工艺为950℃×1 h,空冷＋450℃×3.5 h回火＋350℃×3.5 h回火,可使复合管达到较高的硬度（60～63 HRC）,满足标准DL/T 680—1999《耐磨管道技术条件》的要求。     

拜耳法生产氧化铝流程的物流对能耗的影响

以氧化铝生产流程的基准物流图概念为基础，构筑了拜耳法生产氧化铝流程的基准物流图，为定量分析拜耳法流程中物流对能耗的影响提供了一个比较的基准，并以某拜耳法氧化铝厂生产数据为依据，绘制了该厂的实际物流图，构筑了与其相对应的基准物流图。用基准物流图法定量地分析了各个工序的工序能耗变化和折合比变化对氧化铝综合能耗的影响，以及生产流程中物流对能耗的影响，为指导该厂今后的节能降耗工作提供了定量的依据。     

复杂形状整流罩冲压成形过程优化研究

以某转包整流罩零件为研究对象,对其进行结构分析、拉深成形分析,探讨了成形工艺中的毛坯尺寸的确定、拉深系数的计算、压边力的判断以及拉深力的校核.通过成形过程中的应力特点,并结合拉深冲压理论,摸索类似零件的成形加工经验.研究结果已在生产实践中得到应用,并取得了良好的使用效果,为冲压模具的调整以及成形参数的选取提供了理论与实践依据,从而使成形质量和生产效率大大提高,对实际生产具有很好的指导意义.     

过氧化氢比色法测定棕刚玉中二氧化钛含量的不确定度评定

本文对过氧化氢比色法测量棕刚玉中二氧化钛含量的不确定度进行了评定,分析了测量过程中不确定度的主要来源,如测量重复性、溶液浓度、溶液体积、试样溶液定容体积、分取溶液体积等,并对各不确定度分量进行了量化计算。结果表明:过氧化氢光度法测定棕刚玉中二氧化钛含量不确定度的最主要来源是测量溶液浓度所引入的不确定度,其次是测量方法重复性的不确定度。     

Effects of temperature on fracture behavior of Al-based in-situ composites reinforced with Mg2Si and Si particles fabricated by centrifugal casting

An aluminum-based in-situ composites reinforced with Mg₂Si and Si particles were produced by centrifugal casting Al–20Si–5Mg alloy. The microstructure of the composites was examined, and the effects of temperature on fracture behavior of the composite were investigated. The results show that the average fraction of primary Si and Mg₂Si particles in the composites is as high as 38%, and ultimate tensile strengths (UTS) of the composites first increase then decrease with the increase of test temperature. Microstructures of broken specimens show that both the particle fracture and the interface debonding affect the fracture behavior of the composites, and the interface debonding becomes the dominant fracture mechanism with increasing test temperature. Comparative results indicate that rich particles in the composites and excellent interface strength play great roles in enhancing tensile property by preventing the movement of dislocations.     

粉床型电子束增材制造W-3.5Nb合金孔洞缺陷及其形成机制

采用粉床型电子束增材制造(SEBM)技术制备了W-3.5Nb合金,研究了电子束线能量密度对W-3.5Nb合金孔洞缺陷形成的影响规律,分析了不同类型孔洞缺陷的形成原因.结果 表明:随着电子束线能量密度的升高,缺陷含量降低,当线能量密度升高到1.44 J/mm时,缺陷的体积含量最低为0.01％,继续增大线能量密度,缺陷的体...     

选矿拜耳法氧化铝生产过程中有机物影响的分析与对策

在选矿拜耳法氧化铝生产过程中,采用了浮选方法处理我国中低品位一水硬铝石型铝土矿生产出A/S=10以上的选精矿,选矿使后续拜耳法生产流程的有机物量大大高于常规拜耳法,本文分析了有机物对后续拜耳法生产系统的影响,并提出了具体可行的解决对策。     

Cup-drawing formation of steel sheet with nickel coating by finite element method

The finite element method （FEM） simulation of deep-drawing of steel sheet with nickel coating based on the solid element and dynamic explicit method was reported. Penalty function method was used to treat the contact algorithm. The friction between the punch and coating sheet was based on a Coulomb formulation. The combination of coating and substrate was defined as tied with failure contact. The results of the simulation illustrate that the steel sheet and the nickel coating do not delaminate at the interface. The stress field of the nickel coating is more complicated thala that of the steel substrate. Furthermore, it is found that the punch-nose radius is the most unsubstantial part for the intensity of the entire deep-drawing part and the thinnest part, it is a dangerous zone for the break. At this zone, the thickness thinning of the steel sheet and the nickel coating are up to 4.8% and 6.7%, respectively. Meanwhile, it is found that the curve of the variable blankholder force （VBHF） designed can improve the formability of sheet.