高纯铝定向凝固过程中固液界面特性研究

利用自制的高纯铝定向凝固装置,研究了高纯铝定向凝固过程中固液界面的结构特性。结果表明:晶粒的形态决定了晶间的溶质浓度和偏析出的杂质元素向固液界面的排出速度,其径向分布与固-液界面相对应。由杂质元素分布图可以看出,使用电解铝液做提纯原料,在试验的工艺条件下,Ke值与K0值还有较大的差距,提纯效果的进一步提升需要精确设定温度梯度和冷却速率的工艺条件并有效稳定控制凝固过程的参数匹配。     

金相坑蚀法铝单晶定向研究

采用自制的定向凝固提纯炉制备大直径高纯铝圆锭,锯切获得高纯铝单晶切片。超声探伤确定样片为铝单晶无可见晶界。通过XRD与金相坑蚀实验对比分析获得清晰可见的(111)面三角形位错坑形貌、(220)面矩形铝单晶位错坑形貌及任意晶面的多种位错坑形貌。     

金属连续定向凝固技术

针对日趋活跃的金属定向凝固技术,阐述定向凝固技术的基本原理,以及其特点.简要说明了金属定向凝固技术的应用.介绍了目前金属定向凝固技术在国内外的发展状况,存在的问题及未来的前景.     

基于欧陆温控仪2604和工控机的温度监控系统的通信问题

用定向凝固法提纯铝的关键是精确灵活控制熔体温度场,本文就高纯铝提纯系统的温度监控子系统进行了介绍,重点讨论了子系统中工控机与欧陆温控仪2604间的通信问题.     

超磁致伸缩材料的制备技术研究进展

指出超磁致伸缩材料的制备工艺、性能优化,磁 机耦合过程的理论分析与实验研究,是超磁致伸缩材料研究的两大主题.定向凝固技术是目前国内外广泛采用的超磁致伸缩材料的制备方法.较全面地评述了各种传统的定向凝固技术和新型定向凝固技术的原理和工艺技术特点及存在的问题,提出了一种新的改进型定向凝固技术.     

高纯铝定向凝固短流程提纯设备以及提纯方法

正中国专利CN104561591B本发明介绍了一种高纯铝定向凝固短流程提纯设备以及提纯方法,该提纯设备包括各自独立的提纯装置和加热装置,共同设置在一个大熔炼炉壳内部。本发明具有能耗低、处理量大、提纯效率高、产品纯度高等优点。     

Al2O3/ZrO2(Y2O3)共晶复合陶瓷晶体生长机理

基于国外定向凝固氧化物/氧化物共晶复合陶瓷的晶体生长动力学行为的研究成果,阐述其动力学机制,分析动力学因素对微观结构形态的影响,探讨晶体生长热力学、动力学行为与微观结构形态之间的关系,同时结合以燃烧合成、快速凝固技术制备的新型高强韧Al2O3/ZrO2(Y2O3)共晶复合陶瓷,探讨共晶复合陶瓷在快速凝固条件下的晶体生长动力学行为.结合定向凝固与快速凝固两种晶体生长机制,得知过冷度、凝固界面前沿的温度梯度是影响晶体生长方式的重要因素,且受二者决定的凝固速率(即晶体生长速率)则决定材料的最终微观结构与形态.     

高纯铝的研究进展

超高纯铝比原铝具有更好的导电性、延展性、反射性和抗腐蚀性,在电子工业及航空航天等领域有着广泛用途,目前国内只有极少数厂家能够生产纯度达 99.999%(质量分数）的高纯铝。主要介绍了国内外生产高纯铝的企业、主要生产工艺及生产设备,对国内外高纯及超高纯铝的研究现状及进展情况进行了分析总结。     

金属电磁加工工艺特点及应用

回顾了电磁加工工艺的发展过程,通过分析圆形、椭圆形等不同横截面形状的金属成型制品的电磁成形过程,从感应器结构、屏蔽罩插入深度、材料性状及抽拉速率等方面出发,详细论述了电磁加工定向凝固过程的技术特点,并阐述了电磁成形定向凝固技术的优缺点,指明了今后的发展方向。     

世界高纯铝的生产、市场与应用

本文较为详细地介绍了全世界(含中国)高纯铝的市场概况及应用场合。2003年底全世界高纯铝的生产能力约129kt/a,需求量约74kt。可生产高纯铝的国家:中国、日本、俄罗斯、美国、挪威、德国、法国等。2004年中国高纯铝的生产能力可达38kt/a。高纯铝的75%以上用于轧制电解电容器铝箔。5N级超纯铝的95%用于半导体器件,用作超导体的占5%。4N高纯铝的价格比99.7%重熔锭的高10000元/t),5N高纯铝的价格约比99.7%重熔锭的高62000元/t。     

Progress in Research on Solidification in a Strong Static Magnetic Field

Strong magnetic fields available from superconducting magnets are opening a way to new phenomena that could lead to new methods in materials processing including solidification. The principal research involving solidification in strong static magnetic fields is emphasizing four aspects: control of crystal orientation, convection damping, thermoelectric magnetohydrodynamics (TEMHD) and change in thermodynamics. Under high magnetic intensity, aligned structural textures are induced in both magnetic and non‐magnetic materials. Since in strong magnetic field the melt flow is suppressed by convection damping, the microstructure being formed during solidification is affected heavily; this phenomenon applies to eutectic, monotectic and peritectic alloys as well as to dendritic morphologies typical of directional solidification. If strength and orientation of a magnetic field are controlled appropriately, this strong damping effect will generate more homogeneous crystals as a result of achieving diffusion‐controlled solute transport conditions. TEMHD more easily occurs in strong magnetic fields, resulting in equiaxed crystals even under directional solidification. It is evidenced experimentally and theoretically that the thermodynamics of phase transformation and nucleation are changed by strong magnetic fields.     

超细夹杂物析出研究

非金属夹杂物往往是钢材表面和内部缺陷的成因.但是,当夹杂物的分布适当和颗粒小到一定尺寸时,就能对钢的性能有利.本文研究了氧化物在凝固过程中的析出,采用定向凝固工艺,精确控制了凝固速率,研究了钛、锰、硅及硅-锰复合元素的加入以及冷却速率对夹杂物析出的影响规律.     

高纯铝与铜爆炸焊接性能分析

使用爆炸焊接对高纯铝与铜坯料进行连接,将超声C-scan应用于爆炸焊接复合板坯的无损探伤,并从坯料微观组织和力学性能等方面分析了焊接性能。结果表明,C-scan能够在不破坏板坯的情况下,全面快速检测爆炸焊合率;焊接完成后,铝板坯晶粒间有条状应力带,热处理后应力带消失且晶粒未异常长大。爆炸焊接能实现高纯铝与铜的高强度焊接,焊接强度约43MPa。     

Effects of a High Magnetic Field on the Microstructure of Ni-Based Single-Crystal Superalloys During Directional Solidification

High magnetic fields are widely used to improve the microstructure and properties of materials during the solidification process. During the preparation of single-crystal turbine blades, the microstructure of the superalloy is the main factor that determines its mechanical properties. In this work, the effects of a high magnetic field on the microstructure of Ni-based single-crystal superalloys PWA1483 and CMSX-4 during directional solidification were investigated experimentally. The results showed that the magnetic field modified the primary dendrite arm spacing, γ′ phase size, and microsegregation of the superalloys. In addition, the size and volume fractions of γ/γ′ eutectic and the microporosity were decreased in a high magnetic field. Analysis of variance (ANOVA) results showed that the effect of a high magnetic field on the microstructure during directional solidification was significant (p < 0.05). Based on both experimental results and theoretical analysis, the modification of microstructure was attributed to thermoelectric magnetic convection occurring in the interdendritic regions under a high magnetic field. The present work provides a new method to optimize the microstructure of Ni-based single-crystal superalloy blades by applying a high magnetic field.     

多晶硅锭的制备及其形貌组织的研究

研究了采用定向凝固法制备多晶硅锭的凝固速率与表面形貌、晶粒尺寸以及显微组织缺陷的关系。找出了晶锭不出现细晶的临界生长速度 ,并对固液界面形状进行了探讨。多晶硅锭的制备工艺主要包括定向凝固法及浇铸法。采用定向凝固法制备多晶硅锭 ,通过改变降埚速率控制晶体生长速度 ,进而找出晶粒大小与降埚速率的关系 ;同时通过改变石英坩埚、石墨托厚度 ,冷源半径等几何参数来达到控制固 液界面形状的目的。     

铝合金铸件定向凝固过程的数值模拟

为了研究铝合金定向凝固组织的变化规律,采用有限元软件ProCAST对Al Si Cu合金定向凝固过程进行模拟,分析了不同浇注温度和抽拉速率对铸件定向凝固过程中的温度梯度、固液界面前沿、糊状区宽度、枝晶生长速率和二次枝晶臂间距的影响。结果表明,当浇注温度越高时,温度梯度越大,而固液界面前沿下凹越小,糊状区宽度也越窄,从而越有利于顺序凝固的发生;随着抽拉速率的增大,枝晶生长速率先增大后减小,当抽拉速率为200 μm/s时,最大生长速度达到0.093 mm/s,铸件凝固组织最佳;当抽拉速率大于300或小于200 μm/s时,都会导致枝晶生长速率缓慢,枝晶生长不平稳,二次枝晶臂粗大。对模拟得到较优的工艺参数进行试验验证,可以制备出具有较好力学性能的铸件。     

Yield point behavior in extruded aluminum rod

The microstructure of aluminum, extruded under industrial conditions at 250°C has been investigated in relation to the purity of the billet. Electron microscopy was used to observe the substructure and Kikuchi diffraction techniques were used to measure boundary angles and thus distinguish between recrystallization and repolygonization for samples of two different purities (99.7 pct Al and 99.99 pct Al) extruded under identical conditions. High tensile flow stresses of about 8000 to 9000 psi (55 to 62 MN/m²) were observed in specimens taken from the first sections of the high purity extrusion. These high strength levels were attributed to the presence of fine microstructure. When small recrystallized grains (0.5 to 2.0 μm diam) were present a yield drop was observed. This phenomenon is associated with the condition where nearly all the dislocations are likely to be immobile. The absence of a yield point in the 99.7 pct purity aluminum extruded under the same conditions as the 99.99 pct purity aluminum is due to the existence of fine subgrains instead of the fine recrystallized structure. A small yield point in 99.7 pct aluminum was induced by subsequent heat treatment resulting in the formation of small recrystallized grains of similar character to those in the higher purity extrusion.     

高纯钨研究现状及制备工艺方法综述

高纯钨具有很高的附加价值,其市场前景与集成电路发展密切相关,高纯钨的净化是目前高纯钨生产中的重要研究课题。简要介绍了国内外高纯钨的生产现状、制备工艺及其纯度表征,在此基础上进行了展望。