Hydrogen-enhanced stress-corrosion cracking of aluminum alloys

We present the results of the investigation of Al-Zn-Mg and Al-Zn-Cu-Mg alloys in NaCl solutions at low strain rates. The contribution of hydrogen to the process of stress-corrosion cracking is analyzed by taking into account the influence of the admixtures of arsenic trioxide and residual hydrogen (remaining after the processes of release and cathodic polarization) on the susceptibility of metals to this kind of cracking. A mechanism of hydrogen-assisted stress-corrosion cracking taking into account the time dependence of the microstructure of grain boundaries, concentration of hydrogen, and its distribution is suggested on the basis of the concept of critical concentration of hydrogen. Technical University of Gdansk, Poland. Published in Fizyko-Khimichna Mekhanika Materialiv, Vol. 34, No. 4, pp. 20–26, July–August, 1998.     

快速测定铝及铝合金中含铁量的分析法

采用铁的次灵敏线,分析精密度准确度都较好,操作又十分简捷。建立了快速测定铝及铝合金中含铁量的分析方法。     

Structure of rapidly solidified aluminum alloys

This paper is a summary of an extensive research program carried out by the authors on the structure of rapidly solidified aluminum alloys; and a comparison with the work of others also involved in this field. The paper discusses the changes in the dendritic and non-dendritic structure of the matrix at cooling rates from 10^–3 to 10¹⁰ K/s and discusses the hetergeneity of the structure caused by interdendritic-segretion during solidification.     

Degassing of aluminum alloys during re-melting

The evolution of porosity during re-melting of near-eutectic casting Al alloys has been investigated in-situ using X-ray micro-focus radiography. During re-melting process, gas bubbles float out of the melt quickly when the liquid melt interface passes through them. Based on the degassing phenomenon from the real-time observation, several re-melting experiments were carried out with pure aluminum and a hypoeutectic Al-7%Si-0.4%Mg (A356) in addition to the near-eutectic Al-13%Si alloys. The results clearly show that the area fraction of porosity in the final Al castings decreases dramatically after re-melting one or two times, of which the mechanism is discussed in this paper.     

Stress-corrosion crack growth in aluminum alloys

A macroscopic study of the growth of a stress corrosion crack in an aluminum alloy was undertaken by using the optical method of caustics. The dependence of the crack-tip stress intensity factors K_I on the applied stress, as well as on the molarity of a NaCl aqueous solution was studied in detail. The calculation of these quantities was made by taking into account the thickness variation of the specimen due to the corrosive environment. A criterion of the crack growth in terms of the caustics obtained by illuminating the cracked specimen by a light beam was formulated and the corresponding values of the threshold stress intensity factor K_ISCC were accurately determined. Finally, the creation and the evolution of the pits developed at the vicinity of the crack tip was studied and their significance on the mechanisms of fracture of the specimens was examined.     

Wettability of TiC by commercial aluminum alloys

The effect of alloying elements on the wettability of TiC by commercial aluminum alloys (1010, 2024, 6061 and 7075) was investigated at 900°C using a sessile drop technique. Wetting increased in the order 6061 < 7075 < 2024 < 1010 for both, static argon or vacuum atmospheres. Alloys 1010 and 2024 wet TiC under both atmospheres, leading to contact angles in the order of 60° and less, while 7075 only wets under vacuum, with the poorest wettability being exhibited by 6061. Evaporation of Zn and Mg under vacuum conditions contributed to the rupture of the oxide film covering the aluminum drop and thereby improving wetting and spreading. Continuous and isolate Al₄C₃ was detected in all the cases. CuAl₂ precipitation at the interface slightly decreased Al₄C₃ formation and increased the adhesion of 2024 to TiC.     

Highly resistant icephobic coatings on aluminum alloys

Aluminum alloys are widely used for outdoor structures such as ground wires and phase conductors of overhead power lines, as well as aircrafts wings and fuselage. To protect these surfaces against excessive ice accumulation, icephobic coatings must be highly reliable and durable. New coatings with icephobic characteristics and excellent mechanical properties have been developed. The method consisted in depositing an extremely adherent poly(tetrafluoroethylene) (PTFE) coating on an Al₂O₃ underlayer produced by anodizing in a phosphoric acid electrolyte followed by an oxide etching step to enhance surface roughness. PTFE impregnation was carried out at low temperature (320 °C) and coating adhesion was assessed using tape and bend tests. Some of these coatings showed superhydrophobic properties; ice adhesion was around four times lower than bare aluminum. As well, they remained effective after ten ice-shedding events using an aggressive centrifugal technique. Moreover, no sign of PTFE degradation after 14 ice removals was noted and the coatings remained extremely adherent and very hydrophobic. This technique therefore shows very good potential and could be applied to new high-voltage overhead aluminum cables as protection against excessive ice or snow accumulation.     

锆微合金化增强铝合金的研究进展EI北大核心CSCD

锆(Zr)元素是铝合金中研究较为深入、实际应用较为广泛的微合金元素之一。由于Zr在铝中具有低的固态扩散速率且可形成低密度、高熔点、低界面错配度的Al_(3)Zr弥散相,因此合金展现出高温下服役的潜力。然而,Al_(3)Zr粒子的弥散强化效果主要受到粒子低数量密度或体积分数的制约;此外,多元合金体系凝固、变形、热处理过程中多组元间交互作用复杂,Al_(3)Zr弥散强化与各体系中本征相强化作用往往难以兼得,上述问题均对合金的力学强度造成了不利的影响。本文综合近年来的相关报道,对含Zr铝合金中Zr的存在形式、析出和粗化行为以及强化机制进行了概述;简要介绍了复合微合金化促进Al_(3)Zr析出机理与最新研究结果;对某些体系铝合金中Zr微合金化的应用进行了归纳与总结,结合当前新型耐热铝基合金发展的新趋势,指出铝合金内Zr的微量添加对调控微结构、提升室温和高温强度的重要意义。     

铝及铝合金表面处理研究进展

铝合金耐磨性差、特殊条件下耐蚀性差的缺点限制了它的进一步利用,对铝合金进行表面处理长期以来一直是扩大铝合金使用范围地行之有效的方法.文章综述了铝合金的各种表面处理方法,比较了它们的优缺点,指出表面氧化是铝合金表面处理的主流,复合处理、纳米化处理将是今后铝合金表面处理的主要研究方向.     

Corrosion protection of aluminum alloys by inhibiting pigments

We show that calcium monohydrophosphate can serve as an efficient inhibiting component of anticorrosive coatings applied on an aluminum-copper alloy. It has been established that the charge-transfer resistance of D16T alloy under the influence of CaHPO₄ solution approaches the value characteristic of a medium with strontium chromate. Calcium monohydrophosphate simulates the behavior of strontium chromate inhibitor, retarding the cathodic and anodic corrosion reactions on the surface of aluminum alloys. __________ Translated from Fizyko-Khimichna Mekhanika Materialiv, Vol. 42, No. 5, pp. 7–11, September–October, 2006.     

低温等离子体改性铝合金及其表面性质的研究

通过在铝合金表面制备等离子体聚合物薄膜以减少蛋白质吸附,提高铝合金生物相容性.采用四乙二醇二甲醚为有机试剂,在电子回旋共振低温微波等离子体条件下,在铝合金表面制备了一层涂层,用X-ray光电子能谱、衰减全反射红外光谱和血浆蛋白吸附试验对涂层进行分析表征.结果表明:铝合金表面沉积的涂层均匀、致密,其化学组成为类PEG结构,主要聚集大量碳氢和碳氧极性键;与改性前相比,等离子体沉积在铝合金表面的类PEG涂层能够有效抵抗蛋白质吸附.     

Electromigration evaluation of aluminum alloys in multilevel metallization

This paper focuses on Ti/Al−2.0%Si−0.5%Cu and Ti sandwiched Al−0.5%Cu metallurgies. The electrical reliability of the two Al alloys was determined by a standard electromigration technique (elevated d.c. current and temperature) utilizing single-level and two-level interconnect structures. Transmission electron microscopy and scanning electron microscopy have been used to characterize the film microstructure formed during processing and the types of failure modes observed electrically. For a linewidth approximating film thickness, the formation of a bamboo microstructure dominated the t₅₀ data. TACT films provided superior performance for a stripe linewidth of 2.7 μm and a maximum chain-link length of 100 μm. The common failure modes of the different metallurgies were described, with the TACT exhibiting extrusion.