Sol-gel synthesis of nanostructured materials based on aluminum oxide with preset texture properties

Different mesoporous nanoarchitectures of aluminum oxide are obtained by heat treatment of the products of a sol-gel process involving an ultrasonic treatment and using polyethylene amine, dodecyl sulfate, and dodecylamine as templates. The structure of the materials has been studied by the methods of low-temperature adsorption of nitrogen and diffraction of X-rays at small and large Bragg angles. Depending on the synthesis conditions, the structure of the pores in nanostructured aluminum oxide can change, with the formation of bottle-like, ordered cylindrical, wormhole-like cylindrical or slit pores. In this case, globular γ-Al₂O₃ particles serve as the primary structural units of the synthesized materials.     

矩形断面铜包铝复合材料的水平连铸直接复合成形

制备断面尺寸为50 mm×30 mm、铜包覆层厚度为3 mm的矩形断面铜包铝复合材料,研究结晶器长度、拉坯速度、芯管长度和一次冷却水流量对矩形断面铜包铝复合材料水平连铸直接复合成形过程的影响。结果表明:当连铸结晶器长度为150 mm、芯管长度为125 mm时,较为合理的拉坯速度范围为75~90 mm/min;当拉坯速度过慢时,铝液的填充不连续,导致芯部铝的收缩或冷隔等缺陷;当拉坯速度过快时,铜铝界面反应严重;当拉坯速度为75 mm/min时,合理的一次冷却水流量为700 L/h,一次冷却水流量大于1 000 L/h导致铝液填充不连续,一次冷却水流量小于400 L/h则导致铜铝界面反应加剧。通过检测芯管出口位置处的石墨内衬温度变化可有效监控铝液的填充行为以及连铸过程的稳定性。     

Electroless Ni-P-CNT composite coating on aluminum powder

Ni-P-CNT composite coatings were deposited on micro-sized aluminum particles using electroless plating technique and the effect of different process parameters on the microstructural characteristics of the produced composite coatings were investigated. The results showed that a uniform Ni-P-CNT composite coating could be successfully deposited on the aluminum particles provided the electroless processing parameters were adjusted carefully. The most favorable coating quality was achieved at bath temperature of 80 °C, bath pH of 5.5 and CNT concentration of 1.25 g/lit. While a higher CNT concentration resulted in increased CNT agglomeration and poor CNT distribution in the Ni-P matrix, a lower CNT concentration resulted in fewer incorporated CNTs. Higher bath temperatures intensified the hydrogen gas evolution during the process and resulted in poor uniformity and presence of porosity in the coating. Low bath pH resulted in poor CNT incorporation and distribution in the Ni-P matrix and clustering of a large part of CNTs out of the coating.     

基于多材质复合铸型的A356铝合金性能调控机制研究

建立变壁厚回字形结构多材质复合铸型,首先,通过对A356铝合金在多材质复合铸型的充型、凝固过程模拟仿真,获得多材质复合铸型铸件充型时间和温度场结果,锆英砂与石英砂、铬铁矿砂与石英砂过渡处凝固时间呈阶梯状递减;且锆英砂与石英砂过渡处及铬铁矿砂与石英砂过渡处铸件凝固时间更短,金属液凝固速度更快。其次,采用电子背散射衍射（EBSD）分析、电子显微探针（EPMA）分析对石英砂、铬铁矿砂、锆英砂复合铸型在重力铸造下A356铝合金铸件断口进行分析并进行抗拉强度测试。结果表明：在相同壁厚时,铬铁矿砂、锆英砂型铸件的晶粒尺寸细小,Al、Mg、Si等元素分布均匀、力学性能提高,断口呈现韧性断裂的特征;同时随着壁厚减小,同种材质砂型铸件晶粒细化、元素分布均匀、力学性能提高,断口呈韧性断裂特征。     

Ceramic composite materials

Conclusion The concept of developing new materials with prescribed properties based on ideas about "building" structures may be realized in creating ceramic composite materials. Creation of heterogeneous composite structures is the main path for achieving high crack resistance (a parameter which mainly governs the operating reliability of structural articles). These structures make it possible to realize energy-consuming processes of the dissipation of work for failure from external forces. The level of properties achieved (crack resistance above 300 N/mm^3/2, strength above 500 N/mm²), and the high permissible operating temperatures make ceramic composite materials irreplaceable for a number of fields of technology. However, the main problems connected with the development of ceramic composites remain unresolved. These are problems for achieving the optimum structure and composition of the interface for components, thermal stability of reinforcing elements, the production cost of both fibers and composite materials, and obtaining highly compact matrices in composite materials reinforced with continuous fibers.Scientific Production Association of the Institute of Aviation Materials. Interbranch Scientific Research Center of Technical Ceramics. Translated from Metallovedenie i Termicheskaya Obrabotka Metallov, No. 2, pp. 36–40, February, 1992.     

汽车用挤压铝材概览

随着低碳经济与低碳交通运输业的发展,汽车轻量化要求日益迫切,多用铝材代替钢与铸铁制造可以实现的零部件是当前最可取的,因为在可替代的轻量化材料中铝的性价比是最高的.对挤压铝材在汽车中的应用作了全面的介绍,而对德国奥拓富申公司(Otto Fuchs KG)研发的系列汽车挤压铝材合金则作了比较详细的阐述,海德鲁铝业公司、日本和韩国在开发、生产与应用汽车热交换挤压铝管方面居世界领先水平.     

铝材在国产大飞机上的应用

激光清洗2024铝合金飞机蒙皮表面漆层过程中,粗糙表面的形成与演化会对漆层与激光的热交互作用及漆层去除机理产生较大的影响.1064 nm脉冲激光逐层除漆过程中,分析了漆层表面形貌与粗糙程度的变化,研究了粗糙表面的产生机理及其演化规律,并通过建立漆层粗糙表面等效分析模型计算分析了漆层粗糙表面对激光吸收率的影响规律. 结果表明,激光除漆过程中不同的去除机理作用后漆层均会出现粗糙表面,且粗糙表面的演化存在一定的规律;逐层除漆时,漆层粗糙表面对激光吸收率有明显增加作用,在激光作用7次后漆层粗糙表面对激光的吸收率增加了32.8%,如果采用固定的初始激光清洗工艺,会因吸收率增大导致铝合金基材产生损伤行为.

     

Advanced hermetic electronic packaging based on lightweight silicon/aluminum composite produced by powder metallurgy technique

Silicon/aluminum(Si/Al) composite is a kind of lightweight electronic packaging material that received a lot of attention in the past 20 years.In this paper,a series of Si/Al composites with lowered coefficient of thermal expansion(CTE) and high thermal conductivity were produced by powder metallurgy(PM).The Si/Al composites are fully dense and have fine Si particles uniquely distributed within pure Al matrix.Three 50%Si/Al composites were designed to have strength in the range of 185-290 MPa to...     

基于神经网络铝基复合材料焊接接头力学性能分析

基于神经网络理论,结合真空扩散焊接过程中的持续时间、温度和压力等焊接参数的影响,建立了可用于铝基复合材料焊接接头力学性能分析的数学模型。该数学模型的预测结果与实测数据间的最大相对误差、平均相对误差和均方误差指标均满足预测要求,且模型有较高的精度和较强的容错能力。利用所建立的真空扩散焊接模型进行仿真,可以分析不同的焊接参数对于焊接接头力学性能的影响,为铝基复合材料的力学性能分析提供了有价值的参考。     

Prediction of density,porosity and hardness in aluminum–copper-based composite materials using artificial neural network

The potential of using feed forward backpropagation neural network in prediction of some physical properties and hardness of aluminium–copper/silicon carbide composites synthesized by compocasting method has been studied in the present work. Two input vectors were used in the construction of proposed network; namely weight percentage of the copper and volume fraction of the reinforced particles. Density, porosity and hardness were the three outputs developed from the proposed network. Effects of addition of copper as alloying element and silicon carbide as reinforcement particles to Al–4 wt.% Mg metal matrix have been investigated by using artificial neural networks. The maximum absolute relative error for predicted values does not exceed 5.99%. Therefore, by using ANN outputs, satisfactory results can be estimated rather than measured and hence reduce testing time and cost.     

铸造钢铁基表面复合材料的研究及其进展

阐述了铸造钢铁基表面复合材料的制备工艺和研究现状,并列举了典型制备工艺的优缺点及应用现状,评述了铸造钢铁基表面复合材料的基体材料和增强材料的选择原则,指出了铸造钢铁基表面复合材料今后研究的方向,并展望了其应用前景.