Electrochemical Deposition and Nucleation of Aluminum on Tungsten in Aluminum Chloride-Sodium Chloride Melts

Electrochemical deposition and nucleation of aluminum on tungsten electrode from AlCl3-NaCl melts were studied by cyclic voltammetry, chronopotentiometry and chronoamperometry. Cyclic voltammetry and chronopotentiometry analyses showed that Al （Ⅲ） was reduced at 200℃ in two consecutive steps in an electrolyte of molten AlCl3-NaCl system with a composition 52：48 molar ratio. The current-time characteristics of nucleation aluminum on tungsten showed a strong dependence on overpotentials. Chronoamperometry showed that the deposition process of aluminum on tungsten was controlled by an instantaneous nucleation with a hemispherical diffusion-controlled growth mechanism. The results could lead to a better understanding of the AlCl3-NaCl melt system that has technological importance in electrodeposition of metals as well as in rechargeable batteries.

Mechanical Characterization of Close Cell Aluminum Foams Reinforced by High Voltages Electro-deposition

The parameters for the electro-deposition of Cu were optimized in order to increase the compressive properties of close cell aluminum. Different values of deposition voltages and times were considered to vary the amount of deposited Cu. The surface morphology of the coating was observed by SEM and the compressive properties were evaluated by MTS. The results show that the coating is more homogeneous and compact with increasing voltage in a certain range, and beyond which, the coating quality decreases apparently. The reason is dedicated to the discharge rate of Cu2+ and nucleus formed in unit time. The compression results show three experienced stages: elastic deformation stage, collapse deformation stage and densification stage. After the electro-deposition of Cu, the elasticity modulus is increased obviously and the platform stress is also increased. Under the same strain, the stress of the aluminum foam with coating is reinforced comparing with the aluminum foam without coating. Furthermore, the platform area is widened apparently. In addition, Cu-SiC nanocomposite coatings are electrodeposited in alumium foams for further improving the mechanical characterization.

Characteristics and properties of metal aluminum thin films prepared by electron cyclotron resonance plasma-assisted atomic layer deposition technology

Metal aluminum （A1） thin films are prepared by 2450 MHz electron cyclotron resonance plasma-assisted atomic layer deposition on glass and p-Si substrates using trimethylaluminum as the precursor and hydrogen as the reductive gas. We focus our attention on the plasma source for the thin-film preparation and annealing of the as-deposited films relative to the surface square resistivity. The square resistivity of as-deposited A1 films is greatly reduced after annealing and almost reaches the value of bulk metal. Through chemical and structural analysis, we conclude that the square resistivity is determined by neither the contaminant concentration nor the surface morphology, but by both the crystallinity and crystal size in this process.

Preparation of heat-resistant aluminum alloy pipe blanks by multi-layer spray deposition

A heat resistant aluminum alloy pipe blank with dimensions of d 700/300 mm×1 200 mm was prepared by the multi layer spray deposition technology. Optical microscopy, X ray diffractometry and transmission electron microscopy were used to analyze its morphologies and microstructures. The results show that the microstructures of the pipe blank are homogeneous and the precipitates are uniformly distributed d 25～70 nm spherical or sphere like Al 12 (Fe,V) 3Si particles, its mechanical properties at room temperature and 350 ℃ after densification by extrusion are σ b=412 MPa, δ =7.6% and σ b=187 MPa, δ =7.6%, respectively. The analyses indicate that the proper match of the motion rates of atomizer and substrate can produce deposited blanks with uniform thickness and relatively high cooling rate.

Thixoforming of 6066 aluminum alloy by multi-layer spray deposition

Two thixoforming technologies of 6066 aluminum alloy (Al 1.37Si 1.37Mg 0.77Cu 0.07Mn ) produced by multi layer spray deposition process were studied. The spray formed materials are of equiaxed and very fine grain (10～20 μm). And the grain size coarsens slower than that of conventional casting materials at temperature below the liquidus, which may relate to high temperature particles distributed along the grain boundaries. Extrusion and hot pressing were used as the thixoforming processes respectively. After extrusion the materials show a microstructure of mean grain size below 20 μm without obvious recrystallization. The mechanical properties achieved via extrusion and pressing in semi solid state attain that of common wrought materials with shorter peak aging time of 4～5 h, about half of that in conventional condition. [

Preparation of spray deposited aluminum alloy sheets via novel rolling technique

A novel ceramic rolling technique was developed to improve the formability of spray deposited porous aluminum alloy sheets,in which the sheet preform was canned and ceramic particulates were adopted as the medium for transferring pressure to make a homogenous hydrostatic stress field. The fractional thickness deformation,fractional longitudinal elongation,and fractional lateral spreading were calculated from the dimensions of samples before and after ceramic rolling. The results show that the flowing of metals in the longitudinal and transverse directions can be restrained during rolling. So ceramic rolling can effectively improve the density of the spray deposited performs. When the thickness reduction ratio is up to about 60%,the full density preforms can be obtained. The effect of the kinds of ceramic particulates,including Al2O3,SiO2 and graphite on the densification behavior of the preforms during rolling was investigated. The results imply that the Al2O3 particles with the size of about 74 μm are most effective.

Preparation and Characterization of Amorphous Layer on Aluminum Alloy Formed by Plasma Electrolytic Deposition(PED)

In this investigation, protective layers were formed on aluminum substrate by Plasma Electrolytic Deposition (PED) using sodium silicate solution. The relation between the thickness of the layer and process time were studied. XRD, SEM, EDS were used to study the layer’s structure, composition and micrograph. The results show that the deposited layers are amorphous and contain mainly oxygen, silicon, and aluminum. The possible formation mechanism of amorphous [Al-Si-O] layer was proposed: During discharge periods, A12O3 phase of the passive film and SiO32"near the substrate surface are sintered into xSiO2(l - x)Al2O, and then transformed into amorphous [Al-Si-O] phase.

Electro-Deposition of Cu on Open Cell Aluminum Foams

This manuscript deals with the electro-deposition of Cu on aluminum foams. Metallic foams are highly porous materials which present complex structure of three-dimensional open cells. This aspect causes strong limitations in mass transport due to electro-deposition technology. Experimental tests were performed to study the influence of the operational parameters on the overall performance of the coated aluminum foams. The experimental findings revealed that the manufactured metal foams were characterized by a high thermal conductivity and low process costs, making these materials very promising in many technological fields. On the basis of the experimental results, analytical models are proposed to predict the quantity and the quality characteristics of the coating.

(Al_(63)Cu_(25)Fe_(12))_p/A356 aluminum alloy composites prepared by spray co-deposition

A novel Al-based composite material (Al63Cu25Fe12)p/A356 was prepared by spray co-deposition. It is revealed that the reinforcement of Al63Cu25Fe12 quasicrystalline particles disperses uniformly in the composite with small crystalline grain structure of about 10μm. The reaction between the Al63Cu25Fe12 quasicrystalline particle and the matrix metal is constrained or depressed because of the high cooling velocity in the process of spray co-deposition. Compared with the composite reinforced by non-continuous ceramics particle, the aging harden behavior of the composites of (Al63Cu25Fe12)p/A356 has outstanding characteristics with less time on aging peak happening and with higher hardening rate. The mechanical properties of the composites evidently enhance except plastic strain.

Characteristic of laser-MIG hybrid welding with filling additional cold wire for aluminum alloy

The weld appearance, deposition rate, welding efficiency, stability of arc, laser keyhole characteristic, and weld property were studied by using a novel laser-MIG hybrid welding process with filling wire of aluminum alloy. The results were also compared with those by conventional laser-MIG hybrid welding process. It was found that with the suitable process parameters this novel welding process for aluminum alloy was stable and final weld bead had fine appearance. Compared to conventional laser-MIG hybrid welding process, during this novel welding process the stability of arc, the laser keyhole characteristic and the weld property were similar, while the keyhole cycle frequency and keyhole opening area had differences of 1.23% and 15.34%, respectively, and the welding efficiency increased by about 31% without increasing heat input.

High temperature deformation behavior and mechanism of spray deposited Al-Fe-V-Si alloy

Al-8.5Fe-1.3V-1.7Si alloy was prepared by spray deposition and hot extrusion. The high temperature plastic deformation behavior of the spray deposited Al-8.5Fe-1.3V-1.7Si alloy was investigated in the strain rate range of 2.77×10-4-2.77×10-2 s-1 and temperature range of 350-550 ℃ by Gleebe-1500 thermomechanical simulator. The mechanism of the high temperature plastic deformation of the alloys was studied by TEM associated with the analysis of Rosler-Artz physical constitutive relationship based on the model of dislocation detaching from dispersion particles. The results show that Al-Fe-V-Si alloy has low strain hardening coefficient, and even exhibits work softening. Stress exponent n and activation energy Q were calculated based on Zener-Hollomon relation and Rosler-Artz physical model respectively. The Rosler-Artz physical model can give a good prediction for the abnormal behavior of high temperature deformation of spray deposited Al-Fe-V-Si alloy, that is, n larger than 8 and Q higher than 142 kJ/mol. However, because of the highly refined microstructure, the high temperature deformation behavior of spray deposited Al-Fe-V-Si alloy deviates more or less from the law predicted by using Rosler-Artz physical model.

Effect of heat-treatment on microstructure and properties of SiC particulate-reinforced aluminum matrix composite

The effects of solid solution and aging processing on the microstructures and mechanical properties of the multi-layer spray co-deposited 7090Al/SiCp composite were investigated. The experimented results show that fine grains and homogeneous microstructures can be obtained,the average grain size of the as-solid solution treated and as-aged composites after extrusion is under 3.0 μm. A large amount of the Cu-rich phase particles form in the as-extruded samples,and solve into the matrix after solid solution treatment. After aging,the size of the precipitate phases,mainly MgZn2 and CuAl2 is less than 1.0 μm,which homogeneously distribute inside the grains and at the grain boundaries. The ultimate tensile strength of the composite treated at T6 state,i.e. solid solution treated at 475 ℃ for 1 h then aged at 120 ℃ for 24 h,is up to 765 MPa.

Aluminum doping and dielectric properties of silicon carbide by CVD

Cubic β-SiC coating was grown onto the graphite substrate by the normal pressure chemical vapor deposition using CH3SiCl3(MTS) as a source precursor at 1 150 ℃. But the hexagonal Al4SiC4 phase was generated in the doped process with trimethylaluminium(TMA) as the dopant. Microstructure of the deposit coating as-prepared was characterized by scanning electron microscope(SEM),which consists of spherical particles with a very dense facet structure. The real component of permittivity ε′ and dielectric loss tanδ of the coatings undoped and doped by TMA were carried out by a vector network analyzer in the microwave frequency ranges from 8.2 GHz to 12.4 GHz. The results show that both of them have low values,and doped coating has lower ε′ and tan δ than undoped one due to the existence of Al4SiC4 impurity phase,which indicates that the desired Al/SiC solid solution at 1 150 ℃ in a normal argon atmosphere is not produced.

Densification of Thin Aluminum Oxide Films by Thermal Treatments

Thin AlOx films were grown on 4H-SiC by plasma-assisted atomic layer deposition (ALD) and plasma assisted electron-beam evaporation at 300°C. After deposition, the films were annealed in nitrogen at temperatures between 500°C and 1050°C. The films were analyzed by X-ray reflectivity (XRR) and atomic force microscopy (AFM) in order to determine film thickness, surface roughness and density of the AlOx layer. No differences were found in the behavior of AlOx films upon annealing for the two different employed deposition techniques. Annealing results in film densification, which is most prominent above the crystallization temperature (800°C). In addition to the increasing density, a mass loss of ~5% was determined and attributed to the presence of aluminum oxyhydroxide in as deposited films. All changes in film properties after high temperature annealing appear to be independent of the deposition technique.

Effect of Heat Treatment of Al Substrate on GaN Film Electrodeposited in Aqueous Solution

Most reports on the fabrication of high-quality Gallium nitride (GaN) are typically based on physical techniques that require very expensive equipment. Therefore, the electrodeposition was adopted and examined to develop a simple and economical method for GaN synthesis. GaN films are synthesized on aluminum substrates that are heat-treated at various temperatures using a low-cost and low-temperature electrochemical deposition technique. The electrochemical behavior of source ions in aqueous solutions is examined by cyclic voltammetry (CV).?In the solution at pH 1.5 containing 0.1M Ga(NO3)3, 2.5 M NH4NO3 and 0.6 M H3BO3, reduction of gallium and nitrate ions are observed in CV. The presence of hexagonal GaN and gallium oxide (Ga2O3) phases is detected for the films deposited on Al substrates at -3.5 mA•cm-2 for 3 h. The energy dispersive X-ray and mapping results reveal that Ga, O, and N coexist in these films. Raman analysis shows hexagonal GaN formation on Al substrates. The changes in the morphology and preferred orientation of GaN were found, which was caused by the reactivity of aluminum surface and the aluminum oxide layer formed by the heat treatment.

6061铝合金非连续搅拌摩擦增材制造与性能研究

目的利用非连续搅拌摩擦沉积增材制造技术制备了6061铝合金并研究了z方向非连续搅拌对合金性能的影响。方法使用超景深电子显微镜分析了预热时间对沉积增材成形工艺的影响,并探究了该工艺条件下沉积层的宏/微观缺陷、材料流动及拉伸力学性能关联规律。结果采用z方向非连续搅拌摩擦沉积增材成形工艺,在预热时间为35 s的条件下,除无横向约束的前进侧和后退侧出现了孔洞、弧形飞边及弱结合等微观缺陷外,沉积层中原料棒与凸起搅拌作用区的组织表现为高致密无孔洞的良好形态,原料棒及刀具凸起的强搅拌作用造成z方向材料流动存在差异,进而获得力学性能沿z方向具有梯度分布的完整沉积层,提高了搅拌摩擦沉积增材制造6061铝合金的成形效率。结论在相应的主轴转速(420 r/min)、平移速度(72 mm/min)、进料速度(72 mm/min)、刀具凸起高度(1.5 mm)与预热时间(35 s)工艺参数下,获得了稳定的增材沉积层,有效抑制了沉积层原料棒及凸起搅拌作用区的宏观缺陷,并使材料性能沿z方向呈梯度分布;沉积层抗拉强度达到了原料棒的57.15%;同时伸长率提升了185.8%,为高效率沉积增材及制备梯度性能构件提供了工艺借鉴。

激光定向能量沉积Al-Mg-Sc-Zr修复5083-H112铝合金的组织和性能

激光定向能量沉积增材修复技术具有时间短、效率高、成本低、力学性能好等优点,具有很大的发展潜力。采用Al-7.5Mg-0.3Sc-0.28Zr作为修复材料对轨道交通用5083-H112铝合金进行激光修复实验,得到了致密、无缺陷的修复试样,并对其组织和性能进行研究,探讨了激光修复铝合金的可行性。结果表明,熔合线附近过渡区可划分为修复区、部分熔化区、热影响区和母材。修复区为完全等轴晶,由平均晶粒尺寸为4.95μm的细晶带和18.34μm的粗晶区组成。从修复区到部分熔化区再到热影响区的过渡区域,Al元素含量逐渐升高,Mg元素含量逐渐下降,硬度逐渐下降,修复后母材未被软化。由于激光增材制造技术的快速凝固,在熔合线附近的细晶带有较大的应力集中,由于较小的热输入在部分熔化区、热影响区的残余应力较小。修复试样的屈服强度为(152±2)MPa,为母材的89.4%;抗拉强度为(305±5)MPa,为母材抗拉强度的100%;伸长率为(15.5±0.5)%,为母材的85.2%;断裂发生在强度较弱的母材。高性能的激光修复铝合金是可实现的,具有广泛的应用前景。

酸沉降强度对马尾松土壤活性铝的影响

为探究长期自然环境中酸沉降强度对马尾松林下土壤活性铝的影响,以酸沉降强度依次增大的重庆四面山、缙云山、铁山坪为研究区,选取母质相同的马尾松土壤为研究对象,分析不同酸沉降强度下土壤pH值、营养元素含量、交换性阳离子含量、酶活性与土壤活性铝的相互作用关系。结果表明:随着酸沉降强度的增大,土壤pH值及全碳(TC)、全氮(TN)、交换性铝(Ex-Al)、单聚体羟基铝(Hy-Al)、酸溶无机铝(Ac-Al)含量显著下降(P<0.05),而交换性Mn^(2+)含量不断上升。研究区活性铝以Ac-Al和腐殖质酸铝(Hu-Al)为主,共占比77.1%~84.9%。酸沉降条件下,土壤各形态活性铝含量与TC含量、TN含量、全硫(TS)含量、铵态氮(NH_(4)^(+)-N)含量、脲酶(UE)活性显著相关(P<0.05),活性铝总量的主要影响因子为NH_(4)^(+)-N含量。酸沉降强度改变影响土壤活性铝的主导因子。在四面山,TC、TN、TS含量与各形态活性铝含量显著正相关(P<0.05);在缙云山,Mg^(2+)含量与Ac-Al含量显著正相关(P<0.05),与Ex-Al、Hy-Al、Hu-Al含量显著负相关(P<0.05);在铁山坪,硝态氮(NO_(3)^(-)-N)含量与Ex-Al含量极显著负相关(P<0.01),与Hy-Al、Ac-Al、Hu-Al含量极显著正相关(P<0.01)。随着酸沉降强度的增大,马尾松土壤碳氮元素流失,活性铝淋溶,交换性Mn^(2+)含量升高。经冗余分析可知,随酸沉降强度增大,影响土壤各形态活性含量的主要因子由TC、TN、TS含量转变为交换性Mg^(2+)含量,后为NO_(3)^(-)-N含量。

沉积策略对电弧增材制造5356铝合金显微组织、缺陷和力学性能的影响

基于电弧增材制造技术(WAAM)研究往复扫描(RS)、振荡扫描(OS)和垂直扫描(VS)3种沉积策略对5356铝合金(AA5356)构件的影响,探讨5356铝合金构件的显微组织、缺陷和力学性能。结果表明:相比于RS和OS策略,VS策略使得构件的热量分布均匀。VS策略的显微组织主要由等轴晶组成,使得显微硬度最高值达到HV 77.25。VS策略使得构件的气孔率和微孔尺寸分别下降了45.52%和19.81%,从而改善了拉伸性能。因此,VS策略为获得显微组织均匀、力学性能优异的AA5356构件提供了一种新的解决方案。

金属熔融沉积成型制备7075铝合金的显微组织和力学性能

以优化后的微晶蜡基喂料为原料,通过金属熔融沉积成型制备3D 7075 Al合金。通过热压实验评估蜡基黏合剂和粉末之间的亲和力,研究烧结铝合金的物相、形态演变、拉伸强度和摩擦性能。打印喂料表现出剪切变稀行为,可使熔融挤出过程变流畅,并获得较好表面质量且含少量层间堆积孔隙的3D坯件。在氮气中烧结铝合金的形态演变可分为4个阶段,包括500℃下Mg_(2)Si和Si的沉淀,560℃以上Mg_(2)Si的出现,合金粉末上氧化物层的氮化,以及620℃以上通过扩散过程增强的晶粒生长。3D 7075 Al合金的相对密度达95%,拉伸强度为120~141MPa,拉伸应变为1.0%~2.5%。