快速凝固耐热铝合金的现状与进展

耐热铝合金由于具有低密度、低价格、良好的耐热和耐腐蚀性能,在航空、航天等工业领域得到了广泛应用.回顾了耐热铝合金的发展历程,重点阐述了耐热铝合金的组分选择原则、制备方法及强化机制.分析了其目前存在的问题,并对今后的发展动向进行了展望.     

50th Anniversary Article: The Origin and Management of Residual Stress in Heat‐treatable Aluminium Alloys

The presence of macroscopic residual stresses in heat‐treatable aluminium alloys can give rise to machining distortion, dimensional instability and increased susceptibility to in‐service fatigue and stress corrosion cracking. This paper presents and reviews details about the residual stress magnitudes and distributions introduced into wrought aluminium alloys by the thermal operations associated with heat treatment. Experimental measurement data and the results of finite element analysis are presented and discussed. The available technologies by which residual stresses in aluminium alloys can be relieved are reviewed. The limitations of these techniques are described, and recommendations are made as to selecting the most appropriate technique to manage residual stresses. Opportunities for the future optimisation of these techniques are also presented.     

快速凝固铝硅合金材料及其在汽车中的应用

本文介绍了快速凝固技术的特点及在高硅铝合金中的应用潜力,综述了快速凝固高硅铝合金的制取方法及研究现状,扼要总结了快速凝固高硅铝合金在汽车工业中的应用,最后提出这一研究领域中存在的问题及发展前景。     

Lasererwärmung zur Verbesserung des Umformergebnisses beim Kragenziehen von Aluminium‐ und Magnesiumknetlegierungen

Laser heating for improvement of forming results in hole flanging of magnesium and aluminium wrought alloys Warm sheet metal forming has proven itself for the production of parts made of magnesium and aluminium wrought alloys. In many cases, e.g. in deep drawing, the heating of large surfaces makes sense. If only small areas of a larger part have to be formed, as with hole flanging, a local heating by means of laser irradiation is more advantageous. So the heat quantity can be brought in well metered temporally and locally. The expanding ratio could be increased, depending on material, with a local temperature of about 200 °C by more than double in comparison to cold conditions. It was shown that a narrow process window is to be kept, since material failure arises not only from too low, but also from to high forming temperatures.     

热管技术研究进展及其在制冷空调行业中的应用

综述了国内外热管技术理论研究和应用研究的发展与现状，指出热管技术研究的重心已经从理论研究转移到应用研究，热管的应用已经由航天转向地面，由工业转向民用。在制冷空调行业，热管主要用做换热器，它可以进房间空调器、空调热回收、地热、太阳能、废热利用等技术的应用与发展，将减轻对环境的热污染。     

Metallurgical problems associated with the production of aluminium-tin alloys

Of all the plain bearing alloys available, aluminium alloys have a better combination of ideal bearing characteristics than any other single material. Conventional Babbit alloys, especially the lead bronzes are increasingly being replaced by aluminium alloys, particularly in the automobile industry. It has been known, that the addition of elements, like tin or lead, improves the antiscoring and antifrictional properties of aluminium. Aluminium tin alloys have a wide miscibility gap in the molten state and are virtually insoluble in each other during solidification. Further difficulties arise from the large freezing range of the alloys, which together with the wide density difference between the two components greatly increase the tin segregation during alloy preparation. It has, therefore, been difficult to introduce and uniformly disperse tin in aluminium to the desired extent by conventional melting and casting techniques. The present authors have developed a simple foundry technique which has been used successfully to disperse and retain tin at contents up to 20 wt% in aluminium ingots, which is the subject of the present paper.     

Comparison of experimental, calculated and observed values for electrical and thermal conductivity of aluminium alloys

A model has been developed for calculating the electrical resistivity of commercial aluminium alloys from composition and heat treatments using the Matthiessen rule. The model is based on the approximation that the solubility of the alloying elements in heat treated alloys is equivalent to the equilibrium solubility at a higher temperature. These temperatures were determined from heat treatment data. The resistivity of a wide range of commercial alloys was calculated using the model, showing an agreement with most observed resistivity values of within 3 nΩm, except for alloys with special composition characteristics. According to the model, magnesium and manganese are important contributors to the resistivity for all main groups of alloys. In heat treated alloys the contribution of precipitates is 6–17% of the total resistivity. Thermal conductivity was calculated for alloys given in the literature using the Wiedeman–Franz law and the calculated resistivity. The calculated thermal conductivity agreed with the experimental values for the AlMg-alloys, but it was lower than the experimental values for pure aluminium and the AlCu-alloys in the annealed condition. This revised version was published online in November 2006 with corrections to the Cover Date.     

LNG工程用大截面高压板翅式换热器的技术发展与现状

随着国内外LNG工业的高速发展,对铝制板翅式换热器提出了新的要求,以往小截面、多只并/串连的板翅式换热器组合方案已不能满足大、中型液化天然气工业发展的需要。大截面高压板翅式换热器的换热单元个数少,承压能力高,能够尽量减少气流分配的不均性。大截面高压板翅式换热器的应用,也使得LNG冷箱内管道布置简单,安全性、可靠性大大提高,冷箱体积减小,满足了液化天然气工业发展的需要,也降低了用户投资成本。简介板翅式换热器的技术发展与现状,阐述大截面高压板翅式换热器的热力设计与结构优化。     

Moderne Entwicklungen von Legierungen für den Leichtbau

Modern development of alloys for light weight components Magnesium alloys fulfil the requirements of low density, good formability and machinability and high recycling potential. Nevertheless applications are still well behind those of competing aluminium materials, particularly in the field of composites. The reasons for this are the higher cost of the primary material (exacerbated by the non-existence of a secondary supply), the limited choice of tailor made alloys and composites and partly the insufficient or lost know how in machining and working. There are also knowledge gaps in the user-industries, which prevent a substitution of conventional materials by magnesium alloys. In order to ensure a greater market for magnesium materials in the future by increasing the quality of existing alloys and processes as well as developing new alloys and processes it is necessary to conduct both long term research and development. This paper describes the existing technologies for the production of aluminium and magnesium components and shows some ongoing development of new production techniques.     

新型铝锂合金的微观组织及其在局部腐蚀中的作用

新型铝锂合金由于其低密度、高比强度、高比刚度、高弹性模量、高损伤容限等优良性能日益广泛地应用于航空航天领域。然而,由于特殊的微观组织以及锂元素极高的化学活性,新型铝锂合金容易发生局部腐蚀,严重影响合金构件的使用寿命和安全可靠性。对新型铝锂合金的微观组织及其在合金腐蚀过程中的作用研究进展进行了综述,以期为新型铝锂合金的研究与应用提供一定参考。     

Thermische Nachbehandlung der laserstrahlgeschweißten Al‐Legierungen AlSi1MgMn und AlCu4Mg1

Post heat treatment of the laser beam welded aluminium alloys AlSi1MgMn and AlCu4Mg1 Laser beam welded age hardenable aluminium alloys often exhibit a loss in strength in the fusion and the heat affected zones, compared to the uninfluenced base material. A material‐compatible combination among a base material, a welding filler material, as well as welding parameters and a suitable post heat treatment of the welded joint allows to improve the weld seam properties. The base material AlSi1MgMn (6082) was welded in the aging condition T4 using AlSi12 and AlSi7Mg ‐ filler materials and the welded joint was completely aged at different temperatures and times, in order to adjust an almost constant hardness profile over the base material, heat affected zone and fusion zone. The base material AlCu4Mg1 (2024) was welded in the aging condition T351 using a AlCu6Mn ‐ filler material and the welded joint was naturally aged. The aging behaviour, the residual stress, the static and dynamic properties of welded joints were examined. The properties can be clearly improved by the post heat treatment.     

热交换器用高耐蚀铜合金的研究进展

综述了国内外热交换器用高耐蚀铜合金的研究进展,并对各种耐蚀铜合金的耐蚀性能和适用水质进行了比较,指出了热交换器管材的发展趋势.     

Spray‐Deposited Al‐Si (Osprey CE) Alloys and their Properties

Osprey Metals Ltd. has developed a new family of lightweight, low expansion aluminium‐silicon alloys to suit electronic applications, containing between 30 and 70 wt.% aluminium. They are produced using the Osprey spray deposition process, which achieves homogeneous and isotropic properties. Their advantageous physical characteristics, combining low thermal expansion, high thermal conductivity and low density are particularly suited for packaging electronic circuitry. These CE (controlled expansion) alloys are easy to machine to tight tolerances using standard machine tools and they can be electroplated with gold, silver or nickel finishes without difficulty. This paper focuses on the measurement of mechanical (flexural strength) and thermo‐mechanical properties (CTE, thermal diffusivity and specific heat) of these alloys, carried out in collaboration with AMTT. The property measurements were consistent with those measured previously elsewhere, apart from the CTE values, which deviated significantly and were at variance with values predicted from a rule of mixtures. This discrepancy was resolved in a short follow‐up series of measurements carried out under conditions corresponding more closely to temperature equilibrium.     

LY12铝合金的预形变热处理

轧制方式的预形变热处理,是指对铝合金高温轧制之后,固溶时效处理。它主要是由于热处理之后大量保留了稳定的亚组织,提高了材料的强度、塑性指标,而不降低材料的冲击韧性。本文讨论了铝合金预形热变处理的强韧化机制。     

Umformbare Al-Werkstoffe – für jede Anwendung

Highly Formable Multi-Purpose Al Alloys Microstructural control through appropriate alloy design and definition of processing schedule, as well as a critical view on the interaction of alloy and forming process, has enabled successful application of aluminium alloy sheet in areas where a good formability is a requirement together with an elevated strength level. Further developments along these lines will promote the introduction of aluminium alloys in new markets where, despite its advantages in terms of weight and corrosion resistance, their penetration has been hindered by only moderate formability.     

Magnesium – der Zukunftswerkstoff für die Automobilindustrie?

Magnesium – future material for automotive industry? Magnesium alloys show a very high potential in automotive applications as constructive metal, whereas the main focus lies on die cast parts. Electronic industry is the major commercial consumer for die castings besides the automobile industry. Room temperature applications like steering wheels and frame components in cars as well as mobile phone‐ or notebook housings are well established. These castings are produced with AZ‐ or AM‐magnesium alloys, which show good room temperature properties and a good castability. The great alloy development challenge in extending the use of magnesium cast alloys are application for higher temperatures. The application in powertrain components is considered to be the benchmark here. Besides alloy development there are also further research activities in development of casting processes. Semi‐solid processes like New‐Rheocasting (NRC), Thoxomolding ? or Thixocasting (TC) are adapted to the requirements of newly developed alloys. Not only cast alloys but also magnesium wrought alloys have moved to the centre of interest in the last decade. Alloy development for improving the formability on the one hand as well as process development in extrusion or rolling has to be done in order to find optimum parameters for deforming magnesium alloys properly.     

The influence of post‐heat treatments on the tensile strength and surface hardness of selectively laser‐melted AlSi10Mg

To improve the mechanical properties of cast aluminium alloys several post‐heat treatments are known. However, these treatments cannot directly be transposed to additively via selective laser melting manufactured aluminium alloys, e. g., aluminium‐silicon‐magnesium (AlSi10Mg). Therefore, this study aims to determine suitable post‐heat treatments to optimise the mechanical properties of SLM‐built AlSi10Mg specimen. The influence of various post‐heat treatment conditions on the material characteristics was examined through hardness and tensile tests. The findings indicate that the Vickers hardness and ultimate tensile strength could not be improved via secondary precipitation hardening, whereas the fracture elongation shows a value which is distinctly higher than the values of a comparable cast alloy. Solution annealing at 525 °C reduces the hardness and the ultimate tensile strength by about 40 % and increases the fracture elongation three times. A subsequent precipitation hardening allows recovery of 80 % of the as‐built hardness, and 90 % of the previous ultimate tensile strength combined with maintaining an improved fracture elongation of about 35 % compared to the respective as‐fabricated condition.     

A minichannel aluminium tube heat exchanger – Part III: Condenser performance with propane

This paper reports heat transfer results obtained during condensation of refrigerant propane inside a minichannel aluminium heat exchanger vertically mounted in an experimental setup simulating a water-to-water heat pump. The condenser was constructed of multiport minichannel aluminium tubes assembled as a shell-and-tube heat exchanger. Propane vapour entered the condenser tubes via the top end and exited sub-cooled from the bottom. Coolant water flowed upward on the shell-side. The heat transfer areas of the tube-side and the shell-side of the condenser were 0.941 m² and 0.985 m², respectively. The heat transfer rate between the two fluids was controlled by varying the evaporation temperature while the condensation temperature was fixed. The applied heat transfer rate was within 3900–9500 W for all tests. Experiments were performed at constant condensing temperatures of 30 °C, 40 °C and 50 °C, respectively. The cooling water flow rate was maintained at 11.90 l min⁻¹ for all tests. De-superheating length, two-phase length, sub-cooling length, local heat transfer coefficients and average heat transfer coefficients of the condenser were calculated. The experimental heat transfer coefficients were compared with predictions from correlations found in the literature. The experimental heat transfer coefficients in the different regions were higher than those predicted by the available correlations.     

Determining of laser surface treatment parameters used for light metal alloying with ceramic powders

There are presented in this paper the investigation results of microstructure as well hardness investigation of the surface layer of cast aluminium alloys in as‐cast state and after laser surface treatment using a high power diode laser (HPDL) with Al₂O₃ ceramic powder. The purpose of this work was to determine the proper laser treatment conditions for surface treatment of the investigated alloys and to describe the structural changes occurred in the surface layer after laser treatment. For investigation of the obtained structure there was used light as well scanning and transmission electron microscopy. The morphology and size of the ceramic powder particles as well the structure of the remelted aluminium surface layer was possible to determine. After the laser surface treatment carried out on the aluminium cast alloys there are visible structural changes concerning the microstructure as well as distribution and morphology of the fed particles occurred in the sample surface. Concerning the laser treatment conditions for surface hardening also the laser power and ceramic powder feed rate was studied. The structure of the surface laser tray changes in a way, that there are zones detected like the remelting zone and the heat influence zone. This investigation with appliance of a high power diode laser for Al alloys makes it possible to obtain or develop an interesting technology very attractive for different industry branches.     

Haftfestigkeitsuntersuchungen an galvanischen Niederschlägen

Investigations on the Strength of Galvanic Deposits Pure nickel, nickel alloys, austenitic steel, copper and aluminium alloys were coated with adhesive and heat resisting layers of nickel or copper by electroplating. Production and examination of these metal connections was performed by specially developed methods. The investigations demonstrated, that high quality metal connections can be produced by electroplating. These connections will be of great interest for construction and fabrication.