Effect of ultrasonic vibration on thermal and material flow behavior,microstructure and mechanical properties of friction stir welded Al/Cu joints

Al/Cu dissimilar joint has been widely produced by using friction stir welding (FSW), but the weld quality remains limited. A recently developed ultrasonic     

铝/铜拉拔复合工艺的研究

为了提高Al/Cu复合材料的性能及使用价值,研究了在不同的拉拔工艺参数条件下Al/Cu的复合成形,获得了有利于这2种金属成形的工艺参数.通过对拉拔复合后的Al/Cu双金属棒的扩散退火试验,探讨了热处理规范对双金属复合界面的影响规律.结果表明,拉拔的变形程度对Al/Cu界面复合效果起重要作用,随着变形程度的增加Al/Cu界面复合的效果得到明显改善.拉拔变形程度大于28%的Al/Cu棒复合较好;对于Al/Cu拉拔复合棒可以采用的热处理规范为:温度400 ℃,保温时间2 h.     

超高真空下电流对铜/铝

在销-盘式粘着试验装置上,研究了超高真空下电流对铜/铝接触副静态粘着的影响.结果表明两金属间的粘着随着电流的增大及接触时间延长而增加.考虑因焦耳热引起的接触微峰的熔化作用,对结果进行了探讨.     

Effect of Al2O3 Particle Size on Electrical Wear Performance of Al2O3/Cu Composites

Al₂O₃/Cu composites (1.0 vol%) reinforced with different size of α-Al₂O₃ particles were fabricated by a powder metallurgy method and electrical sliding wear tests were performed on a self-made pin-on-disk electrical wear tester. The effect of Al₂O₃ particle size on electrical wear performance of the Al₂O₃/Cu composite was studied, and the wear mechanism of the Al₂O₃/Cu composite was also discussed based on worn surface observations. The results show that the tribological properties of A1₂O₃/Cu composite are closely related to the mechanical properties. With an increase in Al₂O₃ particle size, the wear rates of A1₂O₃/Cu composites have a reverse variation with hardness of A1₂O₃/Cu composites. In the range of 50–100 nm, Al₂O₃/Cu composites have the highest wear resistance and mechanical properties. Microstructural observation revealed that the wear mechanisms of Al₂O₃/Cu composites were mainly adhesive wear and plastic deformation accompanied by a small amount of arc damage. In addition, the plastic deformation area on the pin sample of the frictional end depends on the electrical wear resistance of A1₂O₃/Cu composites.     

电流对黄铜/Al2O3弥散强化铜合金摩擦副摩擦磨损性能的影响

根据列车受电弓系统的实际工况条件,在自制的销-盘式载流摩擦磨损试验机上研究了Al2O3弥散强化铜合金销试样和黄铜（H62）盘试样摩擦副在载流条件下的滑动摩擦磨损性能,试验条件为速度20m/s、载荷0.63MPa、电流25-75A。试验结果表明,电流对黄铜/Al2O3弥散强化铜合金摩擦副的滑动干摩擦行为具有显著影响。随电流的增加,销试样的磨损率增加,摩擦因数增大,试样表层发生了磨粒磨损和粘着磨损。     

Bimetal cup hydroforming of Al/St and Cu/St composites: Adaptive finite element analysis and experimental study

Journal of Mechanical Science and Technology - An adaptive Finite element analysis (FEA) was proposed in this paper for the industrial design of bimetal conical-cylindrical cup hydroforming....     

超高真空下电流对铜／铝接触副静态粘着的影响

在销-般式粘着试验装置上,研究了超高真空下电流对铜/铝接触副静态粘着的影响。结果表明两金属间的粘着随着电流的增大及接触时间延长而增加,考虑因焦耳热引起的接触微峰的熔化作用。对结果进行了探讨。     

Zr对Zn-Al合金阻尼性能影响的研究

研究了微量Zr对Zn-Al合金阻尼性能的影响，用电阻炉石墨坩埚熔炼了Zn-Al合金和Zn-Al-Zr合金，对合金的显微组织进行了金相观察，用X射线衍射法进行了相结构分析，测量了铸态和淬火态在不同温度及频率的内耗。结果表明：添加微量Zr可以细化合金的铸态组织，但并不改变合金的相结构，无论是铸态还是淬火态下的阻尼性能均得到提高。     

Solid state reaction in sandwich-type Al/Cu thin films

Al/Cu/Al and Cu/Al/Cu triple layers with approximately 10 nm single layer thickness deposited on tungsten substrates were analyzed in the early stages of reactive interdiffusion by means of atom probe tomography. The first reaction product is found after 5 min thermal treatment at 110 degrees C and identified by direct chemical analysis to be Al2Cu. Surprisingly, we found a significant asymmetry in the reaction rate of the new phase with the stacking sequence: the thickness of the product grown at the interfaces, at which Cu is deposited on top of the Al layer, is approximately 1.5-2 times thicker than the other one at the interfaces at which Al is deposited onto a Cu layer. On the other hand, at both interfaces the thickness of the product layer depends parabolically on time. No precursory interdiffusion and no distinct nucleation process of the product are observed.     

Al2O3/Cu复合材料的微动摩擦学特性

以纳米Al2O3为增强相,用粉末冶金法制备了铜基复合材料,研究了Al2O3的比例、载荷等对复合材料摩擦因数和磨损量的影响,并和纯铜的性能作了比较.结果表明,Al2O3的质量分数不宜超过4%,以2%为最佳;纯铜的摩擦因数随着载荷的增加而轻微上升,但Cu/Al2O3复合材料的摩擦因数随着载荷的增加变化幅度较大,呈先上升后下降的趋势,且在极小和较大的载荷下,复合材料的摩擦因数均比纯铜低,但复合材料的磨损量始终比纯铜的低,相对耐磨性最高可达1.55,呈现出良好的耐磨性.     

Galvanic corrosion of Al/Cu meshes with carbon fibers and graphene and ITO-based nanocomposite coatings as alternative approaches for lightning strikes

Earlier airplane fuselages were made primarily of aluminum alloy sheets, which have very good electrical conductivity. If lightning strikes an aluminum alloy surface, the current generated by the lightning can easily flow without interruption or diversion to the interior of the aircraft. Today, fiber-reinforced polymer composites have been widely utilized in aircraft. In order to protect fiber-reinforced composites against lightning strikes, copper (Cu) and aluminum (Al) meshes or metal sheets are used in the uppermost layer. As it is known, carbon fibers are nobler than both Cu and Al meshes, resulting in galvanic corrosion when these dissimilar materials interact with each other under certain environmental conditions. Consequently, corroded metal mesh areas will lose conductivity on the composite surface. For this reason, lightning strike protection is vitally important for the new generation of composite aircraft. In the present study, we systematically studied the galvanic corrosion effects of carbon fibers and metal (Al and Cu) meshes in acidic and salty conditions. We found that environmental conditions had a big impact on the galvanic corrosion between carbon fibers and metal meshes used for fiber-reinforced composites. This paper discusses current lightning strike protection techniques and provides some experimental evidence of graphene and indium-doped tin oxide (ITO)-based nanocomposite coatings on carbon fiber-reinforced composites. This approach may overcome the problem of lightning strikes on composite aircraft and may be useful for redesigning the new generation of composite aircraft.     

Al/Cu异种接头钎焊和扩散焊的研究进展

概述了近年来国内外铜铝异种金属钎焊,特别是真空钎焊和扩散焊焊接技术的研究现状,分析了当前Al/Cu连接存在的主要问题。同时指出,控制Al/Cu接头区域中金属间化合物的生成,将会成为今后Al/Cu焊接研究的重点。     

铝合金点焊过程的铜铝合金化研究

观测了LF2铝合金电阻点焊初期至达到电极寿命时焊点表面及Cr—Zr—Cu电极端面宏观形貌的连续变化过程。采用扫描电子显微镜(SEM)，对机加工状态及抛光处理的电极在点焊铝合金后进行了电极端面背散射分析，对机加工状态的电极在点焊铝合金后又进行了电极端面横向及纵向线扫描分析。采用X射线衍射仪，对沿电极轴向的3个不同电极端面进行了X射线衍射物相分析。结果表明，点焊初期，焊点表面即出现局部熔化及电极端面出现明显凹凸不平，电极端面的形貌及其尺寸发生变化，焊点表面成形质量恶化，电极端面加工状态对电极端面铜铝合金化影响不大，点焊过程电极端面存在较多铝，发生了铜铝合金化反应，合金化产物主要是铜铝金属间化合物(CuAl2)。     

Cu／Al双金属固相结合的实验研究

在大多数情况下，两种金属组合在一起，通过实施成形工艺（例如轧制、拉拔、挤压），两种金属的共同塑性变形便可以使二者形成结合。本文研究了在不同冷挤压工艺参数条件下Ｃｕ和Ａｌ的结合成形，获得了有利于这两种金属成形的工艺参数。通过对挤压成形后的Ｃｕ／Ａｌ双金属进行扩散热处理实验，探讨了热处理规范对双金属界面结合强度的影响规律     

On the effect of asperity-pair elastic joints on friction resistance

One of the exact approaches to the problem of two bodies in contact is the analysis of their composite structure whose stiffness consists of the stiffnesses of the two bulk material bases as well as the interface weak stiffness caused by asperity geometry and junction conditions. In this paper, the material bases are assumed to be rigid compared with a simple elastic joint of surface asperities. The analysis emphasizes the contribution of asperity stiffness to some surface-related phenomena; mainly the significance of shear resistance, interface compliances under combined loading and stickslip motion. If a system of interlocked asperities is sheared by a tangential force, four consecutive phases can be distinguished: stick loading (S1), stick lifting (S2), micro slip lifting (S3) and finally gross sliding (S4). Governing equations of these phases are derived to correlate main parameters of interest with asperity stiffness and geometry. The dependences illustrated here provide more details about motion initiation and sliding resistance.     

Effect of TiB2 particles on sliding wear behaviour of Al–4Cu alloy

Dry sliding wear of Al–4Cu–xTiB₂ (x = 0, 2.5, 5, 7.5 and 10 wt.%) in situ composites have been studied in the peak-aged condition using a pin-on-disc wear testing machine at different loads. The composites were prepared by the reaction of a mixture of K₂TiF₆ and KBF₄ salts with molten alloy. The results indicate that TiB₂ particles markedly improve the wear performance of the Al–4Cu alloy. The wear resistance increases with increase in the amount of TiB₂. The load bearing capacity of the alloy during wear increases in presence of TiB₂ particles. Study of the wear surfaces and debris of both alloy and composites using the scanning electron microscope suggests that the improvement in wear resistance is mainly due to the formation of finer debris.     

Recent development in finite element analysis of clinched joints

Clinching is a high-speed mechanical fastening technique for point joining of sheet materials. Published work relating to finite element analysis of clinched joints is reviewed in this paper, in terms of process, strength, and vibration characteristics of the clinched joints. It is concluded that the finite element analysis of clinched joints will help future applications of clinching by allowing system parameters to be selected to give as large a process window as possible for successful joint manufacture. This will allow many tests to be simulated that would currently take too long to perform or be prohibitively expensive in practice.