Microstructure,Corrosion and Mechanical Properties of Medium-Thick 6061-T6 Alloy/T2 Pure Cu Dissimilar Joints Produced by Double Side Friction Stir Z Shape Lap-Butt Welding

A novel double side friction stir Z shape lap-butt welding(DS-FSZW)process was proposed to achieve excellent mechanical properties of Al/Cu medium-thick dissimilar joints.The influence of welding parameters on weld microstructure and properties of DS-FSZW joint were systematically investigated.It indicated that defect-free medium-thick Al/Cu DS-FSZW joint could be achieved under an optimal welding parameter.DS-FSZW joint was prone to form void defects in the bottom of the second-pass weld.The recrystallization mechanisms at the top and middle of the weld nugget zone(WNZ)were continuous dynamic recrystallization(CDRX)and geometric dynamic recrystallization(GDRX).While the major recrystallization mechanism at the bottom of the WNZ was GDRX.DS-FSZW joint of the optimal welding condition with 850 r/min-400 mm/min was produced with a continuous thin and crack-free IMCs layer at the Al/Cu interface,and the maximum tensile strength of this joint is 160.57 MPa,which is equivalent to 65.54%of pure Cu base material.Moreover,the corrosion resistance of Al/Cu DS-FSZW joints also achieved its maximum value at the optimal welding parameter of 850 r/min-400 mm/min.It demonstrates that the DS-FSZW process can simultaneously produce medium-thick Al/Cu joints with excellent mechanical performance and corrosion resistance.

Improvement of ionic conductivity of solid polymer electrolyte based on Cu-Al bimetallic metal-organic framework fabricated through molecular grafting

A composite solid electrolyte comprising a Cu-Al bimetallic metal-organic framework(CAB),lithium salt(LiTFSI)and polyethylene oxide(PEO)was fabricated through molecular grafting to enhance the ionic conductivity of the PEO-based electrolytes.Experimental and molecular dynamics simulation results indicated that the electrolyte with 10 wt.%CAB(PL-CAB-10%)exhibits high ionic conductivity(8.42×10~(-4)S/cm at 60℃),high Li+transference number(0.46),wide electrochemical window(4.91 V),good thermal stability,and outstanding mechanical properties.Furthermore,PL-CAB-10%exhibits excellent cycle stability in both Li-Li symmetric battery and Li/PL-CAB-10%/LiFePO4 asymmetric battery setups.These enhanced performances are primarily attributable to the introduction of the versatile CAB.The abundant metal sites in CAB can react with TFSI~-and PEO through Lewis acid-base interactions,promoting LiTFSI dissociation and improving ionic conductivity.Additionally,regular pores in CAB provide uniformly distributed sites for cation plating during cycling.

Ni镀层对Cu/Al钎焊接头界面组织与力学性能的影响

为探究Ni-P镀层对Cu/Al异种金属钎焊界面反应的影响,采用化学镀方法对T2紫铜进行化学镀镍处理,使用BAl88Si药芯钎料通过感应钎焊方法钎焊Cu/Al接头。采用扫描电子显微镜和电子背散射衍射技术对接头进行微观组织观察与物相分析,并对接头进行力学性能测试,分析镀层对Cu/Al接头微观组织结构及力学性能的影响,探讨钎焊过程中不同钎焊接头的界面形成机理。结果表明:无镀层接头在界面处形成了Cu_(9)Al_(4)和CuAl_(2)两层金属间化合物,有镀层接头界面处形成了Al_(2)Ni和Al_(3)Ni金属间化合物。无镀层接头的抗拉强度可达56.4 MPa,优于有镀层接头。接头均发生脆性断裂,断裂位置从无镀层接头的CuAl2和α-Al固溶体的界面处转变为有镀层接头的Al3Ni金属间化合物处。

Ni元素对Zn-22Al药芯钎料用于Cu/Al钎焊接头组织和力学性能的影响

目的:研究Ni元素对Zn-Al药芯焊丝熔化特性、铺展性能的影响。方法:在钎剂中添加一定比例的Ni粉,在钎焊过程中形成Cu/Al接头的Ni合金化,分析不同含量Ni元素添加对Zn-22Al钎料以及Cu/Al异种合金钎焊接头的性能及显微组织的影响。结果:Ni粉添加可使Zn-22Al钎料在Al板上的铺展性能得到提升,当添加量质量分数为5%时钎料铺展性能提升26.75%;当添加量质量分数为7%时,用于Cu/Al钎焊的接头抗拉强度相较于未添加Ni粉焊接接头强度提升61.79%。结论:Ni粉添加可有效改善Zn-22Al焊缝的显微组织,体现为主晶相的细化,富Zn边界相的减少,促进主晶团之间形成层片状共析组织,以及减小了Cu侧生成的铜铝金属间化合物脆性相的厚度。

Microstructures and properties of low-melting-point AI-Cu-Si filler metals prepared by different technologies

The Al25 Cu6. 5 SiO. 09RE （RE = La and Ce ） and Al25 Cu10. 5 Si2Ni filler metals were prepared by common metal mold casting, copper plate chilling and rapid solidification, respectively. The microstructures and properties of these filler metals were studied. The results show that the as-casting and the corresponding rapid solidification filler metals have the same phases but their microstructures are different. The microstructure of rapid solidification filler metals consists of an α-A1 solid solution, the θ （ Al2 Cu ） intermetaUic compound and an Al-Cu-Si eutectic phase. Compared with the ns-casting filler metal, the melting temperature ranges （△T） of the corresponding copper plate chilling and rapid solidification filler metals decrease and their wettabilities are improved because of the grain refinement and the improvement of composition uniformity. The wetting area of Al25Cu6. 5Si0. 09RE rapid solidification filler metal doubles that of the corresponding as-casting filler metal. It is hopeful that the properties of Al-Cu-Si filler metals will be improved by changing preparation technology.

Effects of element additions on the microstructure and mechanical properties of Al-Si-Cu filler metals

For the development of a Iow-melting-point filler metal for brazing aluminum alloys, a series of Al-Si-Cu-（ Ni, Sn, Zn ） filler metals have been studied. Through differential thermal analysis （DTA）, the melting temperatures of such Al-Si-Cu- （ Ni, Sn, Zn） filler metals were determined. The results show that the addition of 3 wt. % - 5 wt. % Sn into the Al-6Si-15Cu filler metal causes its solidus temperature to decrease by about 12℃. The filler metal with the composition Al-6Si-15Cu-2Ni is proposed, which possesses a melting temperature range of 512℃ to 520℃ and a microstrueture that includes an Al-Cu eutectic phases, Al-Si-Cu eutectic phases, silicon particles and Cu2Al, AlNi3 , Al7 Cu4Ni and Al3Ni2 intermetallic compounds. An addition of 5 wt. % -7 wt. % Zn into such A1-Si-Cu filler metals cause their solidus temperatures to drop further to a value lower than 498℃. Metallographic observations indicate that the addition of Zn into the Al-Si-Cu filler metal inhibits the formation of the Al-Si, Al-Cu and Al-Si-Cu eutectic phases. The remaining phases are a A12 Cu intermetallic compound, an α- Al solid solution and silicon particles.

热场辅助电磁脉冲焊接Al/Cu异种金属接头组织性能研究

采用热场辅助电磁脉冲焊接技术对Al/Cu异种金属进行焊接,对比分析了热场温度分别为室温、100℃和200℃条件下焊接接头的宏观形貌、界面组织及力学性能。结果表明:热场辅助电磁脉冲焊接技术能够实现Al/Cu异种金属的优质焊接;随着热场温度的增加,焊接接头有效结合区的尺寸增大。而波状界面形貌随着热场温度不同呈现不同的形态,室温下界面呈现正弦波和剪切波的混合波形,100℃下呈不规则的嵌入式波形形貌,200℃下的形貌与室温类似,但是界面反应层的厚度最大;三种温度下的界面反应区都检测到了Al-Cu化合物的存在。力学性能测试结果表明,随着热场温度的升高,焊接接头的力学性能逐渐提高。当加热温度为200℃时,焊接接头的抗拉剪力达到了4076 N;所有试样都在界面处发生断裂,断裂区域存在断口形貌呈现“河流状”和韧窝结构混合形式,推断焊接接头的失效模式为韧脆混合断裂。在外场温度作用下,焊接接头的有效结合区增大,界面波形结构发生改变,进而有效地提升了接头的力学性能。

Al-Cu-Li合金电子束填丝焊接头显微组织与力学性能

采用ER4043焊丝作为填充材料,对厚度为2 mm的Al-Cu-Li合金进行电子束填丝焊,分析测试接头的显微组织与力学性能。在电子束焊过程中,Al-Si焊丝的添加可明显改善焊缝成形和接头质量。微观分析显示,接头焊缝区沿熔合线分布细小的等轴晶,熔合区主要由α(Al)基体相及T_(1)(Al_(2)CuLi),θ′(Al_(2)Cu),T(AlLiSi),β′(Al_(3)Zr),δ′(Al_(3)Li)等强化相组成。焊接时添加电子束扫描可细化焊缝晶粒,有利于提高接头的力学性能。力学性能测试表明,与母材相比,接头熔合区的显微硬度有所降低;焊接时添加方形波电子束扫描,获得接头的抗拉强度为374.7 MPa,达到母材抗拉强度的74.7%。接头拉伸断口表面分布有许多尺寸较大的等轴韧窝,呈韧-脆混合型断裂特征。

Preparation of bimetallic nano-composite by dissimilar friction stir welding of copper to aluminum alloy

Butt friction stir welding between pure copper and AA5754 alloy was carried out.Reinforcing SiC nanoparticles were utilized in friction stir welded(FSW)joints to decline the harmful effects of intermetallic compounds.Tensile tests,micro-hardness experiments,scanning electron microscopy and X-ray diffraction analysis were applied to studying the properties of welded joints.The joints with a travel speed of 50 mm/min and a rotation speed of 1000 r/min showed the best results.The presence of nano-sized SiC particles reduced the grain size of aluminum and copper in the stir zone(SZ)from 38.3 and 12.4μm to 12.9 and 5.1μm,respectively.The tensile strength of the joint in the presence of reinforcing SiC nano-particles was~240 MPa,which is~90%of that for the aluminum base.Furthermore,the highest microhardness of the weld zone was significantly increased from HV 160 to HV 320 upon the addition of SiC nano-particles.The results also showed that raising the heat generation in FSW joints increased the amount of Al_(4)Cu_(9) and Al_(2)Cu intermetallic compounds.

Isochronal and isothermal crystallization in Zr_(55)Cu_(30)Ni_5Al_(10) bulk metallic glass

Non-isothermal crystallization transformation kinetics and isothermal crystallization kinetics in super-cooled liquid region（SLR） in Zr55Cu30Ni5Al10 bulk metallic glasses were studied by differential scanning calorimetry（DSC） and X-ray diffraction（XRD）.In isochronal mode,the average values of activation energy in Zr55Cu30Ni5Al10 bulk metallic glass determined by different models（Kissinger method,Flynn-Wall-Ozawa method and Augis-Bennett method） are in good agreement with each other.In addition,the isothermal transformation kinetics in Zr55Cu30Ni5Al10 bulk metallic glasses was described by the Johnson-Mehl-Avrami（JMA） model.For Zr55Cu30Ni5Al10 bulk metallic glass,the Avrami exponent n ranges from 2.2 to 2.9,indicating that crystallization mechanism in the bulk metallic glass was mainly diffusion-controlled;crystal growth is controlled by long range ordering diffusion in three-dimensional growth during isothermal crystallization process.The average value of activation energy in Zr55Cu30Ni5Al10 bulk metallic glass is 469 kJ/mol in isothermal transformation process.

Structure Evolution of Bulk Metallic Glass Zr_(52.5)Ni_(14.6)Al_10Cu_(17.9)Ti_5 during Annealing

Bulk metallic glass Zr_52.5Ni_14.6Al_10Cu_17.9Ti_5 was prepared by melt injection casting method. Its glass transition and crystallization temperatures were determined by differential scanning calorimetry (DSC) to be 631 K and 710 K respectively. By analysis of X-ray diffractometry (XRD) and transmission electron microscopy (TEM ), the predominant crystallized phase of Zr_2Ni0.67O0.33 distributed on glass state matrix was detected after annealing at 673 K for 600 s. The transformation to Zr_2Ni_0.67O_0.33 and a small amount of ZrAl and Zr_2Cu took place after annealing for 600 s at temperature from 703 K to 723 K. With increasing annealing temperature from 753 K to 823 K, the amounts of ZrAl and Zr_2Cu increased, but the size of the crystals did not significantly change. The transformation to Zr_2Ni_0.67O_0.33 is interface-controlled, but is diffusion-controlled to Zr_2Cu and ZrAl. With increasing annealing temperature up to 200 K above T_x, the nanometer grains became very fine because of the increase of nucleation rate for Zr_2Cu and ZrAl.

Seaweeds as Biomonitoring System for Heavy Metal (HM) Accumulation and Contamination of Our Oceans

This research manuscript reports the heavy metal accumulation in four marine seaweeds sp. 1)?Caulerpa sertlatioides (Cuba);2) Caulerpa cf. brachypus;(Bali, Indonesia);3) Undaria pinnatifida (West-Donegal, Ireland);4) Ulva lactuca (Easters-Scheldt, the Netherlands). Mechanical pressure at 10 bar of fresh seaweed fronds casu quo biomass in the laboratory delivered seaweed moisture which was analyzed by Inductively Coupled Plasma Spectroscopy (ICP)-techniques for heavy-metals = [HM], (Al, As, Cd, Co, Cr, Cu, Fe, Mo, Ni, Pb & Zn). Three important observations were made: 1) The [HM] in the seaweed moisture is higher than in the surrounding seawater which directs to mechanism(s) of bio-accumulation;2) The accumulation factor [AF] is varying per metallic-cation with an overall trend for our four seaweeds and sampling locations for [HM] are: As & Co & Cu: 5000 - 10,000 μg/l;Ni & Zn: 3000 - 5000 μg/l;Cd: 2000 - 3000 μg/l;Cr: 1000 - 2000 μg/l;Al: 200 - 1000 μg/l;Mo & Pb & Fe: 0 - 200 μg/l range. 3) Seaweed moisture detected that [HM]: Pb & Zn & Fe—which all three could not be detected in the seawater—supports the view that seaweeds have a preference in their bio-accumulation mechanism for these three HM. Major conclusion is in general that “overall” for the macro-elements Ca, Fe, K, Mg, Mn, Na, P & S in the moisture of the four seaweed species the concentration is lower in the seaweed species, or equals the concentration, in comparison to the surrounding sea water. For the HM (Al, As, Cd, Co, Cr, Cu, Mo, Ni, Pb & Zn) the opposite is the case species and is the concentration “overall” higher in the seaweed species in comparison to the surrounding sea water. Further topics addressed include strategies of irrigation of the Sahara desert with the moisture out of seaweeds under conditions of low anthropogenic influences.

Phases in the crystallization process of Zr_(65)Al_(7.5)Ni_(10)Cu_(17.5)metallic glass

The crystallization process of metallic glass Zr_(65)Al_(7.5)Ni_(10)Gu_(17.5)(atom fraction in percent) were studied by transmission electron microscopy and X-ray diffraction.Two stages of crystallization process, which are indicated by the two exothermic peaks in thedifferential scanning calorimetry diagram, were studied separately. It is found that the phases inthe various stage of the crystallization are different. In the first stage, it consists mainly oftI-CuZr_2 and tP-Al_2Zr_3 phases, between which a definite orientation relationship is found. Whilein the second stage, in addition to the above phases, phase hP^2-Al_2NiZr_6 and phase hP^3-alpha-Zrappear, between which another orientation relationship is also found. At the same time, a comparisonis made based on the study of the phases exist in the arc-melted master ingot. The latticeparameters of the identified phases were determined and some interesting similarities were found.According to these similarities, all the phases were classified into two groups. The first is: oB,tI-CuZr_2 and hP^3-alpha-Zr; the other is: hP^2, tP-Al_2NiZr_3 and hP^1-Al_2NiZr_6. Therelationships between phases in these two groups were investigated and the probable reasons that mayresult in these relationships were discussed.

Electrical Resistance Measurement of Glass Transition and Crystallization Characteristics of Zr-Al-Cu-Ni Metallic Glasses

In this paper, glass transition and thermal stability of the Zr-AI-Cu-Ni metallic glasses were investigated by using electrical resistance measurement (ERM), DSC and X-ray diffraction techniques. The experimental results show that the ERM is capable of detecting the glass transition of the amorphous alloys and can help to distinguish the crystallization products of the Zr-AI-Cu-Ni metallic glasses owing to the difference of the electrical resistivity between the precipitation phases.

Effects of small amount Ta on the characteristics of the Zr-Al-Ni-Cu-Ta bulk metallic glass

The effects of Ta on the characteristics of the Zr-base BMG (bulk metallic glass) were investigated. Zr55Al10Ni5Cu30-xTax (x=1, 2,4) bulk metallic glasses (BMGs) with 3.5 mm diameter and 70 mm length were successfully prepared by using combined jet and copper mold casting. A small amount of Ta addition does not change the glass transition temperature, crystallization temperature, and supercooled liquid region obviously, but Ta promotes composition separation and two-stage crystallization. The stable crystalline phases include Zr2Ni, CuZr2, Al2Zr3 intermetallic compounds and Ta-rich solid solution after annealing the Zr-Al-Ni-Cu-Ta alloys at 753 K. Zr55Al10Ni5Cu30-xTax (x=1,2,4) bulk glassy alloys exhibit a better compressive strength. The stress-strain curve shows a zigzag feature, and the fracture surface shows intersecting of shear bands. It may correlate with the inhomogeneous feature of amorphous structure.

Cu/Al异种金属连接的研究现状

异种金属接头由于具有优良的性能,因而在许多领域得到广泛的应用,也使得异种金属连接成为当今研究的热点,但铜铝焊接时脆性相的生成,使得铜铝接头的性能很难保证。概述了近年来国内外铜铝异种金属焊接技术的研究现状,针对钎焊和摩擦焊技术做了重点介绍,分析了当前铜铝连接存在的主要困难,对于推动Cu/Al异种金属接头的研究及应用具有重要意义。

Al/Cu管异种材料火焰钎焊连接

采用火焰钎焊技术 ,实现了Al/Cu管异种材料的中温钎焊连接。所采用的改进型的CsF -AlF3 钎剂Si粉含量在 1%时 ,钎焊接头的抗裂性能最好。本试验所采用的钎剂具有熔点低、免清洗、无腐蚀、钎剂活性佳和接头抗裂性能好等优点 。

基于Sn-Pb钎料的Cu/Al钎焊接头组织结构分析

采用金相显微镜、电子探针(EPMA)及X射线衍射仪(XRD)对低温Sn-Pb钎料钎焊Cu/Al异种金属接头的组织结构进行了试验研究,结果表明,钎缝区主要生成Sn-Pb共晶组织及分布于其中的β(Sn)初晶,而在铜侧过渡区生成Cu_3Sn和Cu_6Sn_5两种金属间化合物,在铝侧过渡区生成AlNi、NiSn、Ni_3P及Sn_4P_3等金属间化合物。

钎焊过程原位合成Al-Si-Cu合金及接头性能

Al-Si-Cu基钎料熔点低、强度高,非常适用于铝合金的钎焊。但位于三元共晶成分点附近的Al-Si-Cu合金由于含有大量的CuAl2脆性金属间化合物,无法采用常规塑性加工方法成形,因此限制了其使用范围。为克服上述不足,设计一种使用AlSi-CuAl复合焊丝在钎焊过程中原位合成Al-Si-Cu钎料的方法,并对其钎焊接头组织与性能进行研究。结果表明:采用的复合焊丝外层为AlSi合金,内层为CuAl合金粉,两者熔点接近。复合钎料的加工性能远优于同成分的Al-Si-Cu钎料。使用复合焊丝感应钎焊3A21铝合金,钎焊过程中两种合金几乎同时熔化,经瞬间保温后可充分熔合并形成Al-Si-Cu钎料,获得成分均匀、界面结合良好的钎缝,钎焊接头抗剪强度高于采用常规Al-Si-Cu钎料钎焊的接头抗剪强度。

原位TiC颗粒增强Al-Cu复合材料的组织及性能

以Ｔｉ，Ａｌ和Ｃ粉末为原料，采用接触反应法制备原位ＴｉＣ颗粒增强的铸造ＡｌＣｕ复合材料，研究了反应温度对反应产物的影响，探讨了ＴｉＣ颗粒的形成机制。结果表明，随着反应温度的升高，副产物ＴｉＡｌ３和Ａｌ４Ｃ３生成的可能性减小；当反应温度为９００℃时，反应副产物全部转变为ＴｉＣ，且原位反应生成０．５～１．５μｍ的ＴｉＣ颗粒均布于αＡｌ基体中；ＴｉＣ的加入能显著提高基体的强度，特别是高温强度，但使其延伸率有所下降。