泡沫镍制备中脉冲电沉积镍研究

研究了泡沫镍制备过程中脉冲电沉积镍工艺参数(电流密度、脉冲频率、占空比)对沉积速率、镍沉积层的晶体结构和微观形貌的影响.最佳脉冲电沉积工艺参数为:电流密度2.0 A/dm2,脉冲频率1000 Hz,占空比1∶5.此时获得的镍沉积层结构平整,粒度分布均匀,晶体结构完整.     

脉冲电沉积块体纳米晶Co—Ni合金微观组织结构的研究

利用TEM、XRD、X射线能量散射谱（EDS）、位置敏感原子探针场离子显微镜(PoSAP)等方法研究了脉冲电沉积法制备的块体纳米晶Co-Ni合金的微观组织。结果表明：沉积层中Co含量随电解液中Co^2 离子浓度增加而显著增加;沉积层合金点阵参数随Co含量的增加按Vegard定律增加,同时晶粒尺寸减小;当晶粒尺寸减小到十几纳米时,出现附加的晶格膨胀效应;脉冲沉积与直流沉积相比,晶粒明显细化;PoSAP操作的在线观测和大量数据的计算机三维重构图表明,Co原子在沉积层中呈均匀分布;FIM观察分析表明纳米晶Co-Ni合金中存在三类晶间结构：正常晶界、非长程有序也非短有序的“类气态结构”和少量暗区。     

脉冲电沉积纳米镍镀层摩擦磨损性能的研究

采用脉冲电沉积的方法制备纳米镍镀层,研究了纳米镍镀层的微观组织结构,考察了脉冲电流密度和外加载荷对纳米镍镀层摩擦磨损性能的影响.结果表明,脉冲电沉积方法制备的纳米镍镀层的晶粒均匀致密;电流密度的增大使得纳米镍镀层晶粒尺寸减小,显微硬度和耐磨性提高;随着晶粒尺寸的减小,纳米镍镀层磨损机制从粘着磨损转变为磨料磨损.     

大面积EBSD方法对电解镍板的研究

本文利用大面积EBSD拼接技术,对电解镍板在生长方向上的晶粒形貌及尺寸、择优取向、晶界特征分布等随着沉积的变化进行了研究,并通过SEM观察镍板的微观形貌。结果表明:镍晶粒随着沉积的进行由细小的等轴晶粒转变为粗大的柱状晶,尺寸呈微纳米级;晶体取向在沉积初始没有强的择优取向,最终转变为<001>取向;沉积初期,在大角度晶界占比80%以上,随着沉积进行,大小晶界的比例在沉积层不同位置出现差异;镍沉积层中大量相邻晶粒间以∑3、∑9、∑27孪晶界为界,其中∑3晶界频率达到65%以上。在始极片不同表面形成的镍沉积层长大方式不同,细晶粒表面按照形核长大方式生长,在自由生长的表面镍原子直接并入晶格,没有经历形核过程。     

脉冲电沉积纳米晶镍的力学性能研究

为提高纳米晶镍的显微硬度和抗拉强度,采用脉冲电沉积法制备了不同晶粒尺寸的纳米晶块体镍。利用X射线衍射法分析不同沉积条件的纳米晶镍表面织构和晶粒尺寸。采用超显微微米压痕仪测量表面硬度,利用英斯特朗疲劳试验机进行拉伸试验。结果表明,平均晶粒尺寸为12 nm的纳米晶镍表面显微硬度为598 HV,最大拉伸强度达1360MPa,分别为晶粒尺寸是55 nm的纳米晶镍2.0和1.6倍。另外,晶粒尺寸较小的纳米晶镍伸长率较低。     

高能球磨法制备纳米晶Ni粉的研究

采用高能球磨法制备出了纳米晶镍粉,并利用X射线衍射仪（XRD）、扫描电镜（SEM）、透射电镜（TEM）等分析检测手段,研究了该纳米晶镍粉末的结构、形貌和相的变化。结果表明,镍粉末平均粒度和晶粒度随球磨时间增加不断减小,而应变随球磨时间增加不断增大;当高能球磨54h后,球磨产物为FCC结构的鳞片状多晶体,晶粒度为17nm左右,应变为0.48%,颗粒尺寸为150～200nm;球磨时间增加至98h,产物中出现非晶相,但仍以多晶为主,晶粒尺寸为7nm,应变为1.24%,粉末团聚严重。     

电沉积微纳米镍的组织结构与力学性能

在氨基磺酸镍体系的镀液中通过直流、脉冲电沉积分别制备了不同晶粒尺寸的块体镍.通过室温单向拉伸实验比较了这些镍的力学性能. 结果表明:拓宽电沉积纳米镍的晶粒尺寸分布可显著提高其塑性,同时,保留较高的强度.所制备的具有宽晶粒尺寸分布(5～120 nm)的平均晶粒尺寸为27.2 nm的纳米镍,抗拉强度为1162～1211 MPa,断裂伸长率为10.4%～11.4%.与平均晶粒尺寸为22.4nm的窄晶粒尺寸分布(5～60 nm)的纳米镍相比,抗拉强度降低约200 MPa,但断裂伸长率提高了3.4%.通过对纳米镍微观组织的TEM观察,揭示了宽晶粒尺寸分布纳米镍中塑性的显著提高源于塑性变形中大晶粒(100 nm以上)内存在类似传统粗晶材料中的晶内位错滑移.     

应变诱导Ni原子在纳米晶Fe中的扩散行为研究

利用高能喷丸法（HESP）在工业纯铁表面制备了一定厚度无污染、空位、杂质等缺陷的纳米晶层,其平均晶粒尺寸为50nm,厚度为100μm。在Gleebl 1500热模拟机上,采用脉冲加压扩散(PPD)和恒定加压扩散(CPD)对纳米晶铁在850℃下进行渗镍处理。结果表明,镍原子在纳米晶铁中的扩散系数比常规粗晶中高1个数量级;而采用脉冲加压扩散时,镍原子的扩散系数要比采用恒压扩散高1个数量级。镍原子扩散系数的提高主要包括三个方面的原因,一是脉冲加压能击碎扩撒界面上形成的阻碍镍原子扩散的金属件化合物;二是纳米晶铁中形成的大量三叉晶界以及大量的非平衡晶界。     

多孔Cu/Ni复合材料的电沉积法制备及其性能研究

采用电沉积方法制备了孔隙分布均匀且沉积层从 2到 5 层的多孔Cu/Ni复合材料。研究了不同工艺参数对多孔Cu/Ni复合材料的微观结构形貌和力学性能。多孔Cu/Ni复合材料的微观结构形貌与表征参数与沉积层数密切相关,其平均孔径、孔隙率随沉积层数增加而减小,其比表面积、表观密度随沉积层数增加而增大,多孔Cu/Ni复合材料的铜层与镍层之间由于原子扩散形成固溶体合金层。材料的力学性能随沉积层数增加而提高,压缩强度可达 17.36 MPa,杨氏模量增加 7.9倍,单位体积吸能本领提高13.9倍。     

电沉积宽晶粒度分布纳米镍的组织结构与力学性能研究

通过直流与脉冲电沉积分别制备平均晶粒度为20～30 nm,宽晶粒度分布(5～120 nm)的纳米镍.在室温静拉伸应变速率范围内,直流电沉积制备的纳米镍的平均抗拉强度和平均断裂延伸率分别为1176 MPa与10.6%.而由脉冲电沉积技术制备的纳米镍抗拉强度可达1500 MPa之上,最高断裂延伸率可达13.3%.与电沉积获得的普通窄晶粒度分布的纳米镍相比,宽晶粒度分布的纳米镍的塑性要高出100%以上.其原因是大型晶粒内部允许位错的存在,且理论计算表明,晶内位错可通过Frank-Read源机制进行增殖.     

电铸镍工艺参数对铸镍层组织和性能的影响

利用净化的氨基磺酸盐溶液体系,分别采用金相显微镜、阴极弯曲法和拉伸试验的方法研究了阴极电流密度、溶液温度和p H值等工艺参数对电铸镍层的组织形貌、内应力和力学性能(抗拉强度、延伸率)的影响。结果表明:电铸镍的工艺参数影响铸镍层的组织结构,进而影响到铸镍层的性能;铸镍层的晶粒随阴极电流密度的降低和溶液温度的升高而细化,同时当溶液p H值为4.0时,也可以获得较细的晶粒;随着晶粒的细化,铸镍层的内应力降低,抗拉强度升高而延伸率降低;通过优化工艺参数,获得了抗拉强度为673 MPa、延伸率为23.2%和内应力为48 MPa的综合性能优异的铸镍层。     

复合电沉积工艺参数对镍晶微铸件表面性能的影响

目的将超声波、磁场引入到微电铸过程中,改善电沉积镍晶微构件的表面性能。方法改变电流密度、脉冲占空比、超声波功率、磁场强度的方向和强度,进行电沉积镍晶微铸件,分析这些工艺参数对微铸件表面形貌和显微硬度的影响。结果微铸件的显微硬度随磁场强度的增大而显著提高,随着阴极电流密度、超声波功率及脉冲占空比的增大呈现出先升高、后下降的规律,其中脉冲占空比对电铸层显微硬度的影响较弱。优选的工艺参数为:垂直磁场强度0.8 T,阴极电流密度2 A/dm2,超声波功率240W,脉冲占空比20%。结论引入超声波和磁场后可优化电沉积环境,细化电铸层晶粒尺寸,改善电铸层微观形貌,提高微铸件显微硬度。     

Electro-deposition of oxide-dispersed nickel composites and the behavior of their mechanical properties

Oxide-dispersed nickel composites were produced by electro-deposition of nickel with various types of oxide nano-powders in a sulfamate bath. The effect of the oxide concentration in the bath on the mechanical properties of the electro-deposited composites was studied. The current efficiency of the electro-deposition process was analyzed for different types of oxide nano-powders and for in terms of the amounts embedded in the nickel (Ni) matrix. To evaluate the mechanical strength and the thermal stability, micro-hardness, tensile strength and elongation were measured at room temperature for composites that were heat-treated in a temperature range of 298 K to 1123 K. The results of the experiments showed that a higher oxide powder concentration in the bath led to a greater amount of the oxide particle co-deposited in the nickel matrix. This resulted in higher micro-hardness and improved high-temperature thermal stability. However, an inhomogeneous distribution of the co-deposited oxide powders in the composites was observed to weaken the thermal stability of their tensile strength and elongation.     

预回复对Al-11.5Zn-3.5Mg-2.3Cu-0.24Zr挤压材固溶-T652组织与性能的影响

采用硬度与电导率测试、拉伸试验、晶间腐蚀和剥落腐蚀试验并借助X射线衍射(XRD)、扫描电镜(SEM)、电子背散射衍射(EBSD)等方法,研究了预回复退火对Al-11.5Zn-3.5Mg-2.3Cu-0.24Zr铝合金挤压材固溶-T652处理组织与性能的影响。结果表明:与未经预回复退火相比,预回复退火可有效抑制合金的再结晶,细化晶粒尺寸,降低平均晶界角度,显著提高低角度晶界百分比;预回复退火能够保持同等抗拉强度的情况下,提高该合金的屈服强度和抗腐蚀性能;位错强化和低角度晶界强化是合金屈服强度提高的主要因素。     

含铒铝合金激光焊接接头组织与性能研究

对含铒铝镁合金冷轧板进行了激光焊接,分析了接头的各区域的微观组织和力学性能,探讨了铒对焊缝及热影响区组织与性能的影响。结果表明:由于稀土元素Er的加入,使焊缝中心晶粒尺寸减小到30μm左右;熔合线附近出现"细晶层";热影响区晶粒未见明显长大;焊接接头焊缝截面的显微硬度呈W形分布;Er对焊接接头的抗拉强度提高并不明显,接头抗拉强度为母材的70%。     

Novel application of nanocrystalline nickel electrodeposit: Making good diamond tools easily, efficiently and economically

Electrodeposition has been identified as a feasible and economical technique for nanomaterials application. This article details an improved approach to producing better diamond tools at lower cost and with higher productivity. Pulse-electroformed nanocrystalline nickel was used as the new matrix. The pulse parameters were determined after examination of the microstructure, grain size, hardness and tensile strength of the deposits obtained at different average current densities (J_m) with constant pulse-on time and pulse-off time. It is shown that, with J_m ranging from 1 Adm^− 2 to 14 Adm^− 2, the grain size decreases sharply from 180 nm to about 10 nm while the hardness and tensile strength significantly increase at first and then reach their peaks respectively, although the strength fails to stay long. Current density J_m that produced the highest hardness and strength of deposit (with grain size of 20 nm) was chosen for new diamond tools that exhibited 20.2% longer service life than their usual Ni-Co counterparts. Therefore, nanocrystalline electrodeposits are expected to be an upgrading substitute for conventional polycrystalline matrix.     

The effects of pulse-reverse parameters on the properties of Ni-carbon nanotubes composite coatings

A nickel based composite coatings reinforced with carbon nanotubes (CNTs) were prepared by pulse-reverse electrodeposition. The effects of reverse ratio and frequency on the surface morphology, micro-hardness and corrosion resistance of Ni-CNTs composite coatings were studied. The results showed that higher pulse reverse ratio and pulse frequency made the surface morphology of the coatings more homogeneous. The micro-hardness of the coatings increased with the increase of reverse pulse ratio but decreased with the increase of pulse frequency. Corrosion resistance of the coatings first increases then decreases as the pulse frequency and reverse ratio increase. The best corrosion resistance was obtained for coatings under the condition of 30% reverse ratio and 100 Hz pulse frequency. The effects of CNTs on the properties of the composite coatings were discussed.     

TC4-DT钛合金热机械处理后的组织特征和力学性能

研究热机械处理（两相区变形加普通退火、双重退火、固溶时效以及三重退火）对 TC4-DT 钛合金组织和力学性能的影响。结果表明,热机械处理对显微组织参数影响显著,随着退火和时效温度的升高及冷却速度的降低,初生α相的体积分数和原始β晶粒的尺寸降低,而晶界α和次生α相的宽度却升高。由于固溶时效处理获得了大量的β转变组织和细小的晶界α相和次生α相,合金强度最高,但伸长率不及其它条件的,其断裂强度、屈服强度、伸长率和断面收缩率分别为1100 MPa、1030 MPa、13%和53%,双重退火获得了良好的强度和塑性匹配,合金力学性能分别为940 MPa、887.5 MPa、15%和51%。组织参数和性能的关系表明,随着β转变组织的增多和原始β晶粒尺寸的增大,材料的强度和断面收缩率升高,而晶界α相和二次α相的宽度对力学性能的影响却呈相反趋势。此外,晶界α相含量的减少和原始β晶粒尺寸的降低有助于塑性的提高。     

Strain-rate sensitivity of strength in macro-to-micro-to-nano crystalline nickel

The mechanical behavior of nickel is evaluated over eight-orders of magnitude change in strain rate to see if the change in strain-rate sensitivity exponent is affected by the grain size decreasing from the micron to nanoscale range. Tensile testing is used to measure the strain-rate dependence of the tensile strength on the grain size in crystalline nickel foils. Micro-scratch testing is used to determine the strain-rate dependence of the scratch hardness variation with scratch velocity. It is found that the mechanical test results can be directly compared. The increase in the strain-rate sensitivity exponent that is found with increasing strain rate is slower for nanocrystalline than for microcrystalline nickel foils where strength values begin to converge at the highest strain rates.     

超声波对电镀金刚石工具性能的影响

分别在有超声波和无超声波条件下,制备了镍镀层和电镀金刚石工具。采用显微硬度计测试了镍镀层硬度,采用热震法和锉削法测试镀层与基体的结合强度,用显微镜观察镀层金相组织,计算了工具磨削比。研究结果表明:在电镀金刚石工具制备过程中,应用超声波可以细化镀层晶粒,提高镀层硬度,增强镀层与基体的结合强度。上砂前应用超声波可提高电镀金刚石工具磨粒密度和工具的磨削比。