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，最后提出了这一研究领域中存在的问题及发展前景。     

快速凝固/粉末冶金(RS/PM)高硅铝合金材料的研究

采用冷压 +热挤压工艺制备快速凝固高硅铝合金材料 ,并探讨了挤压温度、保温时间、挤压比等工艺参数对材料组织及性能的影响 .研究结果表明 ,与高硅铝合金铸造材料相比 ,本研究所制的材料硅相尺寸得到了显著细化 ,且分布更为均匀 ,材料的抗拉强度和延伸率有明显的提高 .采用光学金相显微镜、SEM、XRD等手段对快速凝固高硅铝合金粉末及大块材料的微观结构及相组织进行了深入研究 .     

快速凝固耐磨高硅铝合金研究现状

采用快速凝固／粉末冶金技术可制备出高硅含量的铝合金，这种合金具有高耐磨性和低热膨胀性，经合金化后还具有较高的常温和高温力学性能及热稳定性，现已发展成为一系列合金。简述了国内外快速凝固高硅铝合金的研究进展。     

高硅铝合金几种常见制备方法及其细化机理

高硅铝合金根据制备方法的不同,其细化方法及原理也有所不同.主要综述了熔炼铸造、快速凝固粉末冶金和喷射沉积工艺制备高硅铝合金的方法及其细化机理.     

快速凝固耐热铝合金焊接技术的研究现状

阐述了快速凝固耐热铝合金焊接研究现状,分析了快速凝固耐热铝合金的焊接性,讨论了钨极氩弧焊、电容放电焊、电子束焊、激光焊、摩擦焊以及钎焊在快速凝固耐热铝合金材料连接中的应用和存在的问题,指出具有高能量密度、低能量输入的电子束焊、激光焊以及摩擦焊适于快速凝固耐热铝合金的焊接.     

高硅铝合金轻质电子封装材料研究现状及进展

综合比较了现有电子封装材料的性能及其在航空航天领域中的应用现状,较详细地阐述了高硅铝合金电子封装材料的性能特点、制备方法及研究现状,指出了高硅铝合金轻质电子封装材料的发展方向.     

超音速气体雾化高硅铝合金粉末冷却速度计算

通过快速凝固技术制备合金材料,可以大幅度细化合金组织,其技术的冷却速度.本文通过对流换热原理对超音速气体雾化高硅铝合金粉末的冷却速度进行了理论计算,结果表明其冷却速度大约在104～107K/s之间,说明利用超音速气体雾化制备高硅铝合金粉末可以达到很高的冷却速度;另外,通过测定合金粉末内部凝固枝晶间距,并利用冷却速度和枝晶间距之间的经验关系,确定合金冷却速度,其结果与理论计算基本相符.     

高硅铝合金中初晶硅形态控制研究进展

初晶硅形态对高硅铝合金性能具有重要影响,其形核长大机制、形态演化机制是高硅铝合金的主要研究内容之一;尽管已有诸如变质剂处理、半固态搅拌、快速凝固、电脉冲处理等可改善初晶硅形貌的方法,但目前要完全实现控制初晶硅形态并使之球化,使用现有工艺较为困难.综述了目前主要的控制初晶硅形态的方法、研究现状及其控制机制,并对其未来的研究方向提出了一些建议.     

快速凝固过共晶铝硅合金的显微组织及摩擦学行为研究现状

过共晶铝硅合金由于具有高耐磨性、低热膨胀系数和高比强度而广泛应用于汽车和飞机制造业.该类合金在常规铸造下易产生粗大的脆硬初生硅相,降低合金力学性能及耐磨性.而利用快速凝固技术能够有效细化硅相,制备出高耐磨的过共晶铝硅合金.过共晶铝硅合金的性能可以通过改变共晶硅和初晶硅的形态及其分布、二次枝晶胞的尺寸或臂间距等方式加以改善.目前过共晶铝硅合金的研究大多是关于控制共晶和初晶硅的形态和分布,而针对常规铸造的细化晶粒工艺只对25％(质量分数)硅含量以下的过共晶铝硅合金有明显效果,因此研究人员聚焦于能对高硅含量的过共晶铝硅合金实现晶粒细化的快速凝固技术.快速凝固技术区别于常规铸造的特点是高冷却速度,研究发现冷却速度对过共晶铝硅合金的相平衡和微观结构有着显著的影响.随着冷却速度的增加,过共晶铝硅合金的微观结构细化、化学均匀性提高、固溶度增加,形成非晶及亚稳相,极大地改善了过共晶铝硅合金的性能.根据不同快速凝固技术制备的过共晶铝硅合金,其细化的显微组织及对应的摩擦学行为也有所不同.这些差异对于完善快速凝固过程中硅晶粒形核长大机制、形态演化机制及其对过共晶铝硅合金性能影响的理论体系能够起到有效的补充作用.本文综述了快速凝固过共晶铝硅合金四种主要制备方法:衬底急冷技术、快速凝固-粉末冶金技术、喷射沉积技术和选择性激光熔化技术,分析了相关快速凝固工艺的研究现状,对比了不同工艺制备的过共晶铝硅合金的显微组织及耐磨性能,并从理论体系、性能预测和技术工艺三方面对其未来的研究方向提出了一些可行建议.     

快速凝固7000系超高强铝合金的研究现状

在对传统7000系高强铝合金分析的基础上,着重阐述了快速凝固超高强铝合金的发展过程、存在问题和研究现状.快速凝固技术可有效细化组织、提高合金元素的极限固溶度、抑制宏观和微观偏析,并提高超高强铝合金的综合性能,最后提出了快凝超高强铝合金的应用和发展前景.     

Influence of silicon and magnesium on grain refinement in aluminium alloys

Abstract

Grain refinement in Al–Si alloys with silicon contents in the range of 0·2–30 wt-% has been studied in detail with conventional as well as higher level additions of a Al–5Ti–1B master alloy. A poisoning effect was observed with Al–Si alloys containing ≥7 wt-%Si and the extent of poisoning increased with an increase in the silicon content. Silicon improves the grain refining behaviour of aluminium when added in small quantities (0·2%). Magnesium can counteract the poisoning effect of silicon. The optimum level of magnesium required to overcome the poisoning effect depends on the silicon content of the alloy. Higher level additions of a grain refiner could overcome the poisoning effect of silicon and the level required to achieve good grain refinement is a function of the silicon and magnesium contents of the alloy. The present paper also reports the influence of degasser and melt temperature on the grain refining response of Al–Si alloys.     

Crystallographic orientation relationships between primary silicon and aluminium crystals

Crystallographic orientation relationships between the primary silicon crystal and the aluminium crystal heterogeneously nucleated on the silicon surface in hypereutectic Al-Si alloys, were studied by the micro-focus X-ray diffraction analysis. The apparently random orientation relationships obtained by X-ray analysis have been classified into simple relationships by taking the twinning in the primary silicon crystals into consideration. The epitaxial relationships between silicon and aluminium crystals in untreated alloys, and that in sodium-treated alloys, are found to be distinctly different.     

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。     

Ageing and toughness of silicon carbide particulate reinforced Al-Cu and Al-Cu-Mg based metal-matrix composites

Metal-matrix composites (MMC) comprising powder aluminium alloys reinforced by particulate ceramic are being developed for widespread aerospace structural applications ranging from fuselage and missile components to undercarriage parts. Most interest is centred on MMCs with an Al-Cu-Mg (2124) matrix alloy. These MMCs possess high levels of specific stiffness with high specific strengths but can exhibit lower ductility and toughness than conventional unreinforced aluminium alloys.To overcome these problems the effects of alloy composition on the ageing behaviour and notched tensile properties of Al-Cu-Mg and Al-Cu based alloys reinforced with 20 wt% silicon carbide particulate have been investigated.Al-Cu-Mg MMCs gave higher strengths and moduli than unreinforced sheet. Lowering the copper and magnesium content resulted in reduced strength but did not affect the rate of age hardening. The Al-Cu-MMCs gave the lowest strengths but the absence of natural ageing may prove advantageous, enabling sheet to be formed and subsequently heat-treted to the peak strength condition.     

Das Verhalten von Aluminium-Werkstoffen in der Hausinstallation

The corrosion behaviour of aluminium alloys . The corrosion behaviour of the aluminium alloys AlMgMn, AlMgSi 0,8 and AlZn 1 was investigated at two temperatures in two natural waters with different contents with and without oxygen. These measurements were performed as well separated as in contact with copper, brass, iron and zinc; the electrode potentials and the galvanic currents were measured and registrated. The results of the metallographic investigations concerning pitting corrosion of the aluminium samples and of the measurements under potentiostatic conditions were summarized in especial corrosion diagrams. Out of these the corrosion risks of the aluminium materials can be seen. The investigated aluminium alloys – except AlZn 1 – showed unpolarized a good corrosion resistance. The best of them was AlMgMn. In contact with iron and copper containing alloys aluminium were polarized in anodic direction depending of the different metals and of oxygen content of the water. The limit of the pitting corrosion has been exceeded at times. In the cold waters zinc polarized the aluminium alloys cathodic. References were given for applications of aluminium building parts in the home installation and it was informed about experiences which corresponds with these results.     

A review on selective laser sintering/melting (SLS/SLM) of aluminium alloy powders: Processing,microstructure, and properties

Manufacturing businesses aiming to deliver their new customised products more quickly and gain more consumer markets for their products will increasingly employ selective laser sintering/melting (SLS/SLM) for fabricating high quality, low cost, repeatable, and reliable aluminium alloy powdered parts for automotive, aerospace, and aircraft applications. However, aluminium powder is known to be uniquely bedevilled with the tenacious surface oxide film which is difficult to avoid during SLS/SLM processing. The tenacity of the surface oxide film inhibits metallurgical bonding across the layers during SLS/SLM processing and this consequently leads to initiation of spheroidisation by Marangoni convection. Due to the paucity of publications on SLS/SLM processing of aluminium alloy powders, we review the current state of research and progress from different perspectives of the SLS/SLM, powder metallurgy (P/M) sintering, and pulsed electric current sintering (PECS) of ferrous, non-ferrous alloys, and composite powders as well as laser welding of aluminium alloys in order to provide a basis for follow-on-research that leads to the development of high productivity, SLS/SLM processing of aluminium alloy powders. Moreover, both P/M sintering and PECS of aluminium alloys are evaluated and related to the SLS process with a view to gaining useful insights especially in the aspects of liquid phase sintering (LPS) of aluminium alloys; application of LPS to SLS process; alloying effect in disrupting the surface oxide film of aluminium alloys; and designing of aluminium alloy suitable for the SLS/SLM process. Thereafter, SLS/SLM parameters, powder properties, and different types of lasers with their effects on the processing and densification of aluminium alloys are considered. The microstructure and metallurgical defects associated with SLS/SLM processed parts are also elucidated by highlighting the mechanism of their formation, the main influencing factors, and the remedial measures. Mechanical properties such as hardness, tensile, and fatigue strength of SLS/SLM processed parts are reported. The final part of this paper summarises findings from this review and outlines the trend for future research in the SLS/SLM processing of aluminium alloy powders.     

含钪超高强铝合金的研究现状及发展趋势

钪是优化铝合金性能最有效的微量元素,概述了钪对超高强铝合金组织性能的作用机理:细化铸态组织,阻碍再结晶,提高合金力学性能、焊接性能及抗应力腐蚀性能.结合国内外含钪铝合金的研究,指出了今后含钪超高强铝合金的发展趋势.     

快速凝固高强高导铜合金的研究现状及展望

本文综述了快速凝固高强度高导电率铜合金的研究现状 ,并对将来的发展趋势作了展望。指出 ,快速凝固铜合金的凝固过程对合金的最终显微组织结构起重要作用 ,因而 ,对其进行深入细致的研究具有重要意义。     

Influence of high aluminium content on the mechanical properties of directionally solidified multicrystalline silicon

The purpose of this research is the mechanical characterisation of multicrystalline silicon crystallised from silicon feedstock with a high content of aluminium for photovoltaic applications. The mechanical strength, fracture toughness and elastic modulus were measured at different positions within the multicrystalline silicon block to quantify the impact of the segregation of impurities on these mechanical properties. Aluminium segregated to the top of the block and caused extensive micro-cracking of the silicon matrix due to the thermal mismatch between silicon and the aluminium inclusions. Silicon nitride inclusions reduced the fracture toughness and caused failure by radial cracking in its surroundings due to its thermal mismatch with silicon. However, silicon carbide increased the fracture toughness and elastic modulus of silicon.     

New filler metals and process for fluxless brazing of aluminium engineering alloys

Abstract

Many high strength aluminium engineering alloys cannot be joined by brazing because they either degrade or melt at the temperature at which commercially available aluminium brazes are used. A brazing process suitable for joining aluminium engineering alloys has been developed employing two novel low melting point brazes. The brazes are available as ductile foil preforms. The process is fluxless and no post-joining cleaning treatments are necessary. The aluminium components and the brazing foil require a simple chemical treatment before use. The brazing process is tolerant and can be satisfactorily implemented by heating to a temperature of 510–550°C, maintained for a period of 5–45 min, in either vacuum or a furnace chamber that is purged continuously with nitrogen gas. The joints exhibit high strength and adequate resistance to corrosion for most applications. Some promising new applications for aluminium brazing technology based on this new process are described.

MST/3183