Structure uniformity and limits of grain refinement of high purity aluminum during multi-directional forging process at room temperature

The effect of forging passes on the refinement of high purity aluminum during multi-forging was investigated. The attention was focused on the structure uniformity due to deformation uniformity and the grain refinement limitation with very high strains. The results show that the fine grain zone in the center of sample expands gradually with the increase of forging passes. When the forging passes reach 6, an X-shape fine grain zone is initially formed. With a further increase of the passes, this X-shape zone tends to spread the whole sample. Limitation in the structural refinement is observed with increasing strains during multi-forging process at the room temperature. The grains size in the center is refined to a certain size （110 μm as forging passes reach 12, and there is no further grain refinement in the center with increasing the forging passes to 24. However, the size of the coarse grains near the surface is continuously decreased with increasing the forging passes to 24.

Effect of nano TiN/Ti refiner on as-cast and hot-working microstructure of commercial purity aluminum

A novel type nano TiN/Ti composite grain refiner （TiN/Ti refiner） was prepared by high energy ball milling, and its effect on as-cast and hot-working microstructure of commercial purity aluminum （pure Al） was investigated. The results show that TiN/Ti refiner exhibits excellent grain refining performances on pure Al. With an addition of 0.2% TiN/Ti refiner, the average grain size of pure Al decreases to 82 μm, which is smaller than that of pure Ti and Al 5Ti 1B master alloy as refiners. The microstructure of weld joint of pure Al with 0.1% TiN/Ti refiner is fine equiaxed grains and the hardness of weld joint is higher than that of the base metal. For pure Al with 40% cold deformation and recrystallization at 250 °C for 1.0 h, the grains of the sample added 0.1% Ti powder have an obvious grain growth behavior. In contrast, oriented grains caused by deformation have been eliminated, and there is no obvious grain growth in pure Al refined with 0.1% TiN/Ti refiner, indicating that nano TiN in the refiner inhibits the growth of grain during recrystallization.

Modification Behavior of Trace Rare Earth on Impurity Phases in Commercial Purity Aluminum

Modifying effect and mechanism of trace rare earth on Fe(Si) rich impurity phases in commercial purity aluminum were studied with the aids of SEM, EDAX, TEM, etc. It is found that Ce rich mixed rare earth (RE) is an effective modifying agent, which makes the coarse Fe rich impurity phases transform into complex compounds of tiny, sphere/short stick form, thus improving mechanical properties of this material; its modifying mechanism is in that RE gathering in front of solid/liquid interface enters into the impurity phases, forming complex (AlFeSiRE) compounds; or is adsorbed in the impurity phases surface, impeding the growth of impurity phases; however, excessive RE will result in the increasing of RE compounds (secondary phases), and plasticity reduction of this material. Therefore, its addition amount should be less than 0 07% (mass fraction).

Performance comparison of AlTiC and AlTiB master alloys in grain refinement of commercial and high purity aluminum

For further knowledge about the refining performance of AlTiC master alloys, Al5.5Ti0.25C and Al6.5Ti0.5C master alloys containing high Ti and C content were prepared and used in grain refining experiments of 99.8% commercial pure aluminum(CPAl). Their performance was compared with two types of Al5Ti1B refiners whose performance was nowadays considered to be the best. These two types of master alloys show similar refining efficiency at the addition level of 0.2%. However, at the addition level of 0.5%, there still exists great performance difference between AlTiC and Al5TiB alloys in grain refinement of 99.98% and 99.995% high purity aluminum(HPAl). The growth of columnar grains is fully suppressed due to the refinement of AlTiC at the addition level of 0.5%. Also, at the same addition level, the grain refining experiments of Al3Ti0.15C and Al5Ti0.2C master alloys which have found initial commercial applications are conducted in the above-mentioned three types of pure aluminum. According to the experimental results, these two refiners of different compositions are both nonideal. The second phase particles extracted from each refiner were observed through TEM, while the nuclei of grains after grain refinement were observed through SEM. The results were analyzed through computation and comparison of the constitutional-supercooling parameter and the growth-restriction parameter whose values were determined by solute element in aluminum melt with different purity. Apparently, AlTiC master alloys with high content of Ti and C element have great refining potential.

Effect of Process Parameter Variation on Purity during Rotary Fractional Crystallization of Aluminum

High pure and ultrapure Aluminum is increasingly used in highly corrosion resistant applications or to replace copper in conductive parts such as high voltage cable and transformers due to their higher electrical conductivity properties. Ultrapure Aluminum is also used in semiconductors industry. Hence, the market demands innovative refining technologies, which consume less energy, take less time and lead to higher resource efficiencies. The most common methodology to produce ultrapure Aluminum is zone refining, based on the principle of fractional crystallization. Zone refining is however a very time-consuming process. In order to achieve a purity of 6N, several passes along the crucible with each full day treatment must be carried out. Also this method cannot be conducted continuously. This paper presents first time a new and eco-efficient method, which offers high potential to meet the mentioned multi-dimensional demands. Firstly, distribution coefficients of main impurities in Aluminum—a deciding factor to forecast and assess the removal behavior of impurities-were studied theoretically as a function of temperature using thermo-chemical calculation in FactSageTM. Secondly, the innovative method using a rotating and gas cooled crystallizer (“cooled finger”) was developed to validate the principle. The influencing process parameters such as temperature gradient, cooling gas flow rate, etc. were experimentally investigated and the theoretical results could be verified.

Nucleation and growth of high purity aluminum grains in directional solidification bulk sample without electromagnetic stirring

A self-made directional solidification device was used to fabricate d 80 mm high purity aluminum ingots. SEM and AFM were used to detect the shape of grain boundaries. The orientation of the grain was studied by X-ray diffractometry. The results show that the nucleation points locate at the intersections of three adjacent grains. The lattice orientation of grains does not alter in the horizontal direction, but gradually approaches the optimum growth direction in the vertical direction during the growth process. All the grains suffer the competition and only the one whose orientation is closest to the preferred direction can occupy the final growth space.

Effects of electric field on recrystallization texture evolution in cold-rolled high-purity aluminum sheet during annealing

The effects of an external DC(direct current)electric field on recrystallization texture evolution in the cold-rolled aluminum sheets with 99.99%purity were investigated by means of X-ray diffraction techniques.The cold-rolled high-purity aluminum sheets were annealed for 60 min at 200,300 and 400℃,respectively with and without an external DC electric field of 800 V/mm.The results show that with DC electric field,the recrystallization cube texture is strengthened at the stage of grain growth. Possible reason for the strengthening of the recrystallization cube texture with the applied electric field may be attributed to both selected nucleation and selected growth of cube oriented crystal nuclei.

Mechanism of strengthening of cube texture for high purity aluminum foils by additional-annealing

The mechanism of strengthening of cube texture ({001}<100>) by additional annealing of high purity aluminum foils was investigated by using orientation distribution functions (ODFs) and electron back scattered diffraction (EBSD). The results of ODFs and fiber show that the orientation densities of the S {123}<634> and Cu {112}<111> components increase in both the additional annealed samples and the 0.11 mm final cold rolled foils. And the EBSD results demonstrate that cube nuclei can be identified in the deformed matrix of those additional annealed samples. It is suggested that the strengthening of cube texture can be brought out by the increasing of components of S and Cu and the formation of cube nuclei caused by additional annealing. Moreover, it is found that the cube texture increases first and then decreases with increasing additional annealing temperature, and it is the strongest at 180 ℃.The strengthening of cube texture by additional annealing is proposed as the result of oriented growth of cube subgrains.

Effect of Ce on castability,mechanical properties and electric conductivity of commercial purity aluminum

Effects of Ce addition on microstructure, castability （fluidity and hot tearing sensitivity）, mechanical properties and electric conductivity of commercial purity aluminum （CP-AI） were investigated through microstructure observation and performance tests. Results show that adding Ce in a CP-AI can considerably refine the grains, and has an important influence on the amount, crystallographic forms, and distribution of secondary phases. Addition of Ce also has a large impact on the fluidity and hot tearing sensitivity （HTS） of the CP-AI. With the addition of Ce from 0.1wt.% to 0.5wt.%, the fluidity of CP-AI is first increased remarkably and then decreased, and the HTS has an opposite response. The best castability of the studied alloys appears to be at 0.2wt.%-0.3wt.% Ce addition. The remarkable improvement in castability is attributed to the considerable refinement of grain structure. Ce addition can also lead to a significant rise in electric conductivity. The maximum conductivity of the as-cast CP-Al is 59.7% IACS with an addition of 0.2wt.%Ce. The T7 heat treatment can further improves the conductivity to 60.7% IACS. The Ce-induced evolution of the secondary phases is believed to be the mechanism for it.

Recrystallization behavior of high purity aluminum at 300℃

The recrystallization behavior of 98.5% cold rolled high purity aluminum foils annealed at 300 ℃ was investigated,and the evolution of the microstructures was followed by electron back scattered diffraction(EBSD).The results show that the recrystallization process of the high purity aluminum foils at 300 ℃ is a mixture of discontinuous-and continuous-recrystallization.The orientations of the recrystallization nuclei include not only the cube orientation,but also other orientations such as some near deformation texture components which are the results of strong recovery process.However,such continuously recrystallized grains are usually associated with relatively high free energy,so they would be consumed by the discontinuously-recrystallized grains(cube-oriented grains)in subsequent annealing.On the other hand,the pattern quality index of recrystallized grains shows dependence on the crystal orientation which might introduce some errors into evaluating volume fraction of recrystallization by integrating pattern quality index of EBSD.

Development of cube texture in multistage annealing of high purity aluminum foils

The development of cube texture ({001}〈100〉) in high purity (99.99%) aluminum foils in multistage annealing was investigated by ODF and EBSD. It is found that a multistage annealing process can strengthen cube texture markedly, and that each stage of the multistage annealing plays an important eigen role in nucleation and growth of the cube orientation grains. The cube orientation grain nucleates preferably at 180 ℃ because of its low activation energy of nucleation, the cube nuclei grow favorably at 400 ℃ because of the anisotropy of 40°〈111〉 growth. and the cube texture is further strengthened at 550 ℃ and becomes prodominent because of favorable bigger grain sizes.

Competitive growth of high purity aluminum grains in directional solidification

A self-made directional solidification setup was used to prepare high purity aluminum ingots of 100mm in diameter. The morphology of the growth interface was detected by SEM and AFM, and the grain lattice orientation was detected by XRD. The results indicate that the grains suffer competitive growth under any conditions in experiments. The lattice orientation of the preferred grains is determined by the flow field above the solid-liquid interface. The horizontal lattice position does not change during the growth process. However, the lattice orientation in the growth direction varies with the growth velocity and approaches to [100] gradually during the growth process.

集成电路用超高纯铝铸造生产实践研究

超高纯铝铸锭是溅射靶材的上游关键材料,本课题根据生产实践中的对比试验,探究不同原料配比对超高纯铝铸锭的不纯物、颗粒物、内部质量的影响,旨在为生产高品质集成电路用超高纯铝铸锭提供参考。生产实践结果表明,重熔料表面进行清理是必要步骤,随着重熔料在原料中占比升高,铝中颗粒物夹杂数量和尺寸有升高和长大的趋势,在生产实践中重熔料在原料中的占比应该控制在30%以下。

Effect of pre-recovery on microstructure and properties of rolled Al-12.18Zn-3.31Mg-1.43Cu-0.20Zr-0.04Sr aluminum alloy

The independently designed and manufactured ultra-high-strength aluminum alloy Al-12.18 Zn-3.31 Mg-1.43 Cu-0.20 Zr-0.04 Sr was investigated via scanning electron microscopy observations, X-ray diffraction analysis, hardness tests, electrical conductivity tests, tensile tests, intergranular corrosion tests, and exfoliation corrosion tests. The effect of pre-recovery on the microstructure and mechanical properties of this aluminum alloy was also studied. The results show that the pre-recovery heat treatment releases deformation energy, inhibits recrystallization, and decreases the dislocation density. Although the pre-recovery heat treatment has little effect on the hardness, electrical conductivity, and elongation of this aluminum alloy, it can dramatically improve the alloy's tensile strength(the maximum tensile strength increased from 785.0 MPa to 809.2 MPa). Moreover, the tensile properties of this aluminum alloy have a certain degree of isotropy, and the pre-recovery heat treatment does not affect this property. In addition, the rolled aluminum alloy exhibits good corrosion resistance, but the effect of the pre-recovery heat treatment on the alloy's resistance to intergranular and exfoliation corrosion is negligible.

Influence of Purity Degree on the Evolution the Mechanical Properties of Aluminium Commercial

The influence of the purity degree of the commercial aluminium on the mechanical properties： elastic stress, tensile strength, Brinell hardness, resilience and elongation at break was investigated. It was found that the first three resistance characteristics decrease with the growth of the purity of the material chosen to the detriment of two ductility characteristics that rise to the three states considered： crude of casting noted： F, Annealed noted： O, hardened noted ： H1/4. Furthermore, it is important to note that the hardened and the annealed lead respectively to a considerable hardening and a considerable softening. This hardening and this softening of the material in question can be respectively associated with the increase in dislocation density and immigration impurity elements of dislocations.

中子辐照和冷轧(预应变)对高纯铝压缩特性的影响

金属材料的中子辐照脆化一直都是核能安全领域十分关注的问题,辐照硬化效应往往能够定性表征材料的辐照脆化性能.大量冷轧金属被应用于反应堆结构材料,为进一步认识冷轧(预应变)对中子辐照金属材料硬化特性的影响规律及其微观机理,文章研究了退火态和预压缩10%应变高纯铝的准静态压缩性能,以及位错密度,辐照孔洞的尺寸和数密度随辐照剂量的变化规律.结果表明,辐照剂量越高,高纯铝内部孔洞的尺寸和数密度越高,辐照缺陷引起的强化效果越强;预应变引入的高密度位错会抑制辐照孔洞的形核和长大,最终降低孔洞的尺寸和数密度;预应变高纯铝表现出显著的辐照退火效应,随着辐照剂量的增加,辐照退火引起的软化效应明显强于辐照缺陷引起的硬化效应,导致预应变高纯铝的屈服强度随辐照剂量先增加后降低;这一结果暗示退火效应很可能导致辐照冷轧材料的屈服强度低于其未辐照时的初始屈服强度,从而降低反应堆内冷轧态金属结构的安全可靠性.最后,基于Johnson-Cook本构关系的B-Y(Byun-Ye)辐照脆化模型能够适用于辐照金属材料的压缩本构关系预测,且模型预测结果与实验结果吻合较好.

NaOH亚熔盐处理铝电解废阴极炭块

废阴极炭块是铝电解槽大修时产生的危险固体废弃物.以某铝电解企业废阴极炭块为原料,在明确其物相组成的基础上,分别研究了NaOH亚熔盐与各组分的反应机理.采用单因素方法分析了亚熔盐浸出铝电解废阴极炭块过程中NaOH质量分数、浸出温度、浸出时间、氧分压及搅拌速率对浸出渣中碳纯度(质量分数,下同)的影响.研究结果表明:亚熔盐中的O_(2)^(2-)可以破坏废阴极炭块原料中NaAlSiO_(4)和NaAl_(11)O_(17)的晶体结构,同时,高质量分数的NaOH可以与CaF_(2)反应生成Ca(OH)_(2);亚熔盐浸出铝电解废阴极炭块的最优工艺参数为NaOH质量分数50%、浸出温度215℃、浸出时间5 h、氧分压1 MPa、搅拌速率700 r/min,在此条件下浸出渣中碳纯度达到95.6%.

高纯铝电解槽母线配置对熔体区磁场影响的研究

高纯铝在电子工业中有重要应用,电解精炼法是生产高纯铝的主要方法之一。本文对某厂现运行高纯铝电解槽磁场分布进行了模拟计算,并将其与现场测试值进行对比分析。分析后可知,该厂现运行高纯铝电解槽现场测试值与模拟计算值变化趋势完全相同,测试重现性较好,在某些测试点上吻合度较高。这验证了磁场计算方法的可靠性,并用该磁场计算模型为该厂新建槽配置了新的母线系统。相比现有高纯铝电解槽,新建槽四个象限的最大磁场绝对值降幅比例达72%。从计算结果可知,新建槽四个象限的磁场分布更加均匀,远优于现有槽,更加有利于高纯铝生产的降低极距及节能降耗。

Separation and purification of Yb_(2)O_(3) by ion exchange chromatography and preparation of ultra-high purity Yb_(2)O_(3)

Ultra-high purity Yb_(2)O_(3) is the critical material of many high-tech materials such as laser glass and fiber,in which impurities seriously affect the laser color quality,intensity and power.In order to reduce the influence of impurities on the properties of laser materials,the purification process of Yb_(2)O_(3) was studied by comparing two kinds of resins(RT-1 and RS-1)using improved ion-exchange chromatography(IEC)method.In this study,through the synergistic improvement of resin structure and eluting system,the environmental pollution caused by ammonia water in the traditional IEC method was reduced,and the requirements of high temperature and pressure were cut.The ion exchange behavior and impurity removal mechanism in the resin column during the loading and eluting process were compared and analyzed.The experimental results show that RS-1 resin is all superior to RT-1resin in elements selectivity,ion exchange capacity and impurities removal rate.After separation and purification by IEC with RS-1 resin,the total removal rate of rare earth impurities was 77.59%and that of non-rare earth impurities was 95.86%when Yb recovery was more than 70%,both higher than that of RT-1 resin(73.26%and 83.18%).This indicates that the improved IEC method is very effective in separating and removing different metal impurities from Yb_(2)O_(3).The pilot test results of IEC method separating and purifying Yb_(2)O_(3) with RS-1 resin show that the purity of Yb_(2)O_(3) can be increased from 99.9929%to 99.9997%by IEC method.It has exhibited huge potential of preparing ultra-high purity Yb_(2)O_(3),especially the deep removal of non-rare earth impurities.

异丙醇铝水解制备高纯氧化铝

采取异丙醇铝水解制备高纯氧化铝,实验较环保,且异丙醇能重复利用,降低了生产成本。对合成后的异丙醇铝进行检测,硅的含量很高,添加氧化镧后,异丙醇铝的纯度提高,且不改变异丙醇铝的性质,易产物分离。研究表明,异丙醇铝水解实验表明最佳水解条件为55℃时水解3~5 h;产物粉体中的水分在1200℃保温4 h时已全部蒸发,且当粉体煅烧温度的升高时,粉体比表面积和平均粒度也减小;可以利用Ca、Na、Mg去除杂质,提高氧化铝的纯度。