铝铁合金的研究进展与应用状况

综述了Al-Fe合金的国内外研究现状，阐述了共晶、过共晶铝铁合金及其在快速凝固条件下的凝固特点，概述了添加Ca、Mg、Mn、RE等微量元素及采用热速处理、电流处理、交变磁场、超声振动等工艺条件对Al-Fe合金微观组织的影响规律，叙述了目前Al-Fe合金的应用状况，并对铝铁合金的研究及应用前景进行了展望。     

稀土Er对共晶铝铁合金的变质作用

采用热分析方法研究了稀土Er对共晶铝铁合金的变质作用。通过OM、XRD、SEM、EDS以及合金在凝固过程中的特征参数综合分析了稀土Er对共晶铝铁合金的作用机理。结果表明:冷却速率为33℃/s时,共晶铝铁合金的凝固过程为:先发生L→α-Al初转变,然后发生L→Al+Al3Fe和L→Al+Al6Fe共晶转变,添加了稀土Er后,在凝固末期发生L→Al+Al3Er转变而生成铝稀土共晶相。初生的Al3Er可以作为初晶α-Al的非均质形核质点,增加了初晶α-Al的形核率,提高了铝铁合金中初晶α-Al开始形核温度,缩短了共晶转变时间。当Er添加量为0.3wt%时,初晶α-Al平均晶粒尺寸达到了最小值21.7μm。当Er添加量为0.5wt%时,初晶α-Al晶粒尺寸增大,且出现了离异共晶组织。     

FORMATION OF (γ+γ') EUTECTIC AND CONTROL OF σ-PHASE IN A HIGH Al-Ti CAST Ni-BASE SUPERALLOY

高铝钛铸造镍基高温合金的凝固与偏析是极复杂的过程,本文测定了凝固过程中各种相的形成顺序、成分变化及合金元素的分配系数等,着重讨论了(γ+γ′)共晶的形成过程和控制该合金析出σ相的办法。     

一种铸造镍基高温合金中(γ γ′)共晶的形成及σ相的控制

高铝钛铸造镍基高温合金的凝固与偏析是极复杂的过程,本文测定了凝固过程中各种相的形成顺序、成分变化及合金元素的分配系数等,着重讨论了(γ γ′)共晶的形成过程和控制该合金析出σ相的办法。     

高速凝固粉末冶金铝合金(2)

本篇是全文的第二部分,评述国内外工业高速凝固粉末冶金铝合金的发展状况,其中包括:各种高速凝固粉末冶金铝-锂合金的成分和性能,以及它们的制备工艺,重点评述了高模量、高强度铝-锂-铍合金的特点及其应用;各种高速凝固粉末冶金铝-铁耐热合金的成分和性能,重点评述了铝-铁-铈合金和铝-铁-钒-硅合金的特性。     

金属与合金加压凝固研究进展

基于国内外对金属合金加压凝固过程的研究,阐述了加压凝固的原理和实施方法,总结了加压凝固对铁合金、轻合金和铜合金等金属铸件微观组织和力学性能的影响规律。结果表明:加压凝固能够改变金属及其合金的物理参数和结晶过程,改变疏松孔洞的分布和尺寸,提高铸件的致密度,改善铸件的拉伸性能和硬度等;另外,当所施加的压力足够高时,还可以抑制铸铁石墨化过程:改变硅在铝中的固溶度,从而改变Al-Si相平衡。这些结果足以证明加压凝固可以被推广和加深研究,以发挥各向气体压力在凝固科学和金属及其合金成型的重要价值。     

快速凝固过共晶铝硅合金材料的研究进展

快速凝固技术是改善过共晶铝合金组织和提高其性能的有效手段,快速凝固过共晶铝硅合金是具有巨大应用潜力的活塞材料。对快速凝固过共晶铝硅合金材料的成分、组织结构特点,制备理论及工艺,性能及其强化机理进行了综合评述。     

铸态铌铁中的相

用电子探针、X射线衍射仪等设备研究了商用铌铁铸锭中的相。研究结果表明,合金中存在 Fe2Nb、FeNb以及Fe2Nb3 相。在不同牌号的铌铁合金中,各相的成分都不同程度地偏离了其原子配比。铸锭中亚稳Fe2Nb3 相的存在是由于凝固过程溶质元素以及杂质原子在凝固前沿富集的必然结果,也与其晶体结构有关。     

铝与Cu-P合金熔体互溶过程中过渡层熔体凝固组织的研究

将纯铝熔体倒入Cu-P合金熔体,保温30 s后用水激冷。采用Axiovert200MAT金相显微镜和MLA 250(FEI Quanta)扫描电镜(附带能谱仪)观察金相组织,并进行能谱分析。研究了铝与Cu-P合金熔体互溶过程中过渡层熔体的凝固组织,并分析了铝、铜和磷原子的扩散过程。结果表明:铝与Cu-P合金熔体接触后形成的过渡层由L_((Cu-Al-P))+L_((Cu-Al))+AlP组成,凝固后靠近Cu-P合金一侧的凝固组织为Cu_3P_(初生)+(αCu+Cu_3P)_(共晶)+少量的AlP;由于Cu-P合金为过共晶成分,凝固后靠近Cu-P合金一侧P/Cu比变大,使Cu-P合金的过共晶程度增大,凝固组织中初生Cu_3P相数量增多。     

铝与Cu-P合金熔体互溶过程中过渡层熔体凝固组织的研究

将纯铝熔体倒入Cu-P合金熔体,保温30 s后用水激冷。采用Axiovert200MAT金相显微镜和MLA 250(FEI Quanta)扫描电镜(附带能谱仪)观察金相组织,并进行能谱分析。研究了铝与Cu-P合金熔体互溶过程中过渡层熔体的凝固组织,并分析了铝、铜和磷原子的扩散过程。结果表明:铝与Cu-P合金熔体接触后形成的过渡层由L_((Cu-Al-P))+L_((Cu-Al))+Al P组成,凝固后靠近Cu-P合金一侧的凝固组织为Cu_3P_(初生)+(α_(Cu)+Cu_3P)_(共晶)+少量的Al P;由于Cu-P合金为过共晶成分,凝固后靠近Cu-P合金一侧P/Cu比变大,使Cu-P合金的过共晶程度增大,凝固组织中初生Cu_3P相数量增多。     

Improving design for recycling – Application to composites

The use of composite material increases. End of life regulations, material consumption reductions or restrictions, ask engineers about their potential use. Innovative recycling solutions arise that recover efficiently carbon fibres. This paper explores the design for composites recycling issue. Recycler becomes a new knowledge expert for the designer. It is necessary to analyze their information shares and exchanges. The recycler is an end of life facilitator. He is also the second life material user and can ask for material evolutions. The collaboration must be improved using knowledge performance indicators. These discussions will be enlightened by examples from carbon recycling experiments.     

Composite materials parts manufacturing

Composite materials parts manufacturing is based on the interactions of simultaneous as well as consecutive process steps. These influence the composite part properties and economical production. A wide range of possible composite materials and processing technologies necessitate a holistic view of the product life cycle to ensure the best possible economic and ecological outcome. Current studies on new manufacturing and machining processes aim for higher productivity and machinability, whereas new quality control approaches are enhancing the desired product quality. Furthermore, recent research addressing joining concepts and recycling methods has a huge impact on competitiveness and sustainability. Focusing on latest academic research approaches and current industrial application fields, this paper gives an overview of various process steps in the overall product life cycle of composite materials parts manufacturing.     

Anomalous reheating behavior of SiCp/Al composite with high volume fraction reinforcement

The reheating behavior of 50 vol.% SiCp/Al squeeze casting composite was investigated at temperatures ranging from 600°C to 900°C using XRD and SEM techniques from the microstructural point of view. It was found that SiCp/Al composite could hold its original shape while being reheated at temperatures elevated even far above the melting temperature of pure Al. The high volume fraction of SiC reinforcement, which would restrict the fluidity of molten Al matrix and the reconfiguration of SiC particles during the reheating of SiCp/Al composite, was thought to be responsible for the “remelting resistance” of the SiCp/Al composite. The extent of the reaction between the SiC particles and molten Al was found to increase with increased reheating temperature. From the viewpoint of controlling the formation of aluminum carbide, reheating temperature either for recycling or for remelting processing of the SiCp/Al composite, a temperature lower than 750°C would be better. Despite its being unfavorable to remelting or recycling processing, the remelting resistance of the SiCp/Al composite with high volume fraction reinforcement is attractive for thermal function and high temperature applications.     

Kinetics of the reactions of carbon containing zinc oxide composites under microwave irradiation

As a fundamental study for the recycling of EAF dust using microwave heating, the reduction rate of a zinc oxide composite by solid carbon under microwave irradiation was investigated. It was found that the reduction of zinc oxide by solid carbon under microwave irradiation was much faster than the conventional method, and the activation energy for the reaction under microwave irradiation was estimated to be 335 kJ/mol.     

The recycling and reclamation of metal-matrix composites

The development of viable techniques for the recycling and reclamation of metal-matrix composites (MMCs) is critical to the commercialization of these advanced materials. The recycling of both MMC wrought alloy (6061) scrap and foundry alloy (high-silicon) returns has been studied. The MMC extrusion alloy scrap has been recycled back into direct-chill cast logs and the resulting billet has been tested to determine whether the composite properties are degraded by repeated recycling. Similarly, fluxing and degassing techniques have been developed so that MMC foundry alloy gates and risers produced in shape-casting may be recycled back into useful castings. These fluxing and degassing processes have been tested commercially. Ultimately, when either type of MMC scrap can no longer be recycled, the alumina particles in the wrought alloys or the silicon carbide particles in the foundry alloys may be removed by common salt or other fluxing techniques. Rotary salt furnace technology has been shown to be effective for this approach, and the results of large-scale trials are reported here.     

An additive manufacturing-based approach for carbon fiber reinforced polymer recycling

The vast Carbon Fiber Reinforced Polymer (CFRP) waste accumulated is pressing for its recycling. A novel recycling approach, which integrated carbon fiber reclamation and composite additive manufacturing, is proposed to process the CFRP waste into three Dimensional (3D) parts. In the experiments, the CFRP waste was recycled by supercritical n-butanol to yield reclaimed Carbon Fibers (rCFs). The rCFs were ground by a ball mill, mixed with Poly-Ether-Ether-Ketone (PEEK) powder and then extruded to the composite filament. The filament was fed to the Fused Deposition Modeling (FDM) printer to fabricate 3D parts. Mechanical and electrical properties of the parts were investigated and compared with that of pure PEEK. The results illustrate that the additive manufacturing-based approach offers a potential strategy to reuse the CFRP waste and rapidly fabricate the rCF reinforced plastics with complex geometry and function.     

The effect of reprocessing on the mechanical properties of the waste fabric reinforced composites

In this study, waste cotton fabric reinforced polymer matrix composite plate has been processed by a-custom-made recycling extruder. Two different (12.5% and 25% fibers by weight) waste fabric reinforced composite plates were produced and reprocessed six times to assess repetition effect of processing on the mechanical and rheological properties on plates. Effects of reprocessing were evaluated by the tensile testing and impact testing besides SEM, DSC, XRD and MFI rheological and characterization analysis. Test results of composite plates were compared with the pure low density polyethylene (LDPE) plate. Test results show that the tensile strength was increased till the 4th reprocessing step while reducing impact properties. In further reprocessing, tensile properties have been decreased as a consequence of the fabric/fiber damage. Thermal effect of reprocessing was limited according to the comprehensive characterization and rheological analysis.     

化学退镀的溶解曲线及其应用

防染盐-S对镍有良好的溶解性能而对铁不产生腐蚀作用,是退除铁基体上镍或镍铜复合镀层的理想试剂。探讨防染盐-S退镀液中各成分的作用,给出较优含量,推荐配方及其使用规范。并对废液回收、再生及处理提出建议。     

The development of recycle-friendly automotive aluminum alloys

The continuing growth of aluminum alloy usage in transportation applications, notably passenger automobiles and minivans, and the demonstrated economic benefits of recycling aluminum-rich vehicles increase the need to seriously consider the desirability of designing recycling-friendly alloys. This article focuses on that aspect of the recycling process for passenger vehicles. The goals are to illustrate the opportunities afforded by identifying and taking full advantage of potential metal streams in guiding the development of new alloys that use those streams. In speculating on several possible aluminum recovery practices and systems that might be used in recycling passenger vehicles, likely compositions are identified and preliminary assessments of their usefulness for direct recycling are made. Specific compositions for possible new recycle-friendly alloys are suggested. In addition, recommendations on how the aluminum enterprise, including industry, academia, and government, can work together to achieve the aggressive but important goals described here are discussed.     

Recycling of automotive aluminum

With the global warming of concern, the secondary aluminum stream is becoming an even more important component of aluminum production and is attractive because of its economic and environmental benefits. In this work, recycling of automotive aluminum is reviewed to highlight environmental benefits of aluminum recycling, use of aluminum alloys in automotive applications, automotive recycling process, and new technologies in aluminum scrap process. Literature survey shows that newly developed techniques such as laser induced breakdown spectroscopy (LIBS) and solid state recycling provide promising alternatives in aluminum scrap process. Compared with conventional remelting and subsequent refinement, solid state recycling utilizing compression and extrusion at room or moderate temperature can result in significant energy savings and higher metal yield.