【作者】 赵阳培；

【导师】 黄因慧；

【作者基本信息】 南京航空航天大学 ， 机械制造及其自动化， 2005， 博士

【摘要】 快速成型技术和纳米材料是当今制造和材料领域的两个重要研究方向。金属零件的快速制造已成为当前快速成型领域的研究热点和快速成型技术的最终目标之一。探索制备高质量的三维大尺寸块体纳米晶体材料工艺方法已成为纳米材料研究的关键技术之一。电铸是一种利用电沉积方法来成型金属零件的精密制造技术,在电铸中采用射流方式可大大提高阴极极限电流密度,显著提高电沉积速度和细化沉积层晶粒。本文将射流电铸和快速成型技术有机结合起来,发展了一种新的直接快速成型金属零件的新方法,进行了纳米晶铜的快速制备和直接快速成型纳米晶铜零件的基础试验研究,并取得了以下的主要结论: (1) 根据电沉积有关基础理论,分析了影响电铸速度的主要因素,总结了提高电铸速度和细化电铸层晶粒的措施,根据射流电铸的流场和电场分布特点分析了射流电铸快速成型的可行性。 (2) 将射流电铸与快速成型技术有机结合起来,发展了一种新的直接金属零件快速成型新方法——射流电铸快速成型技术,研制了射流电铸快速成型设备系统。设计开发了具有脉冲波形好、性能稳定的脉冲电源。 (3) 系统研究了直流电铸工艺参数、脉冲电流、添加剂硫脲以及电铸液中加入纳米Al2O3颗粒时对电铸层表面形貌的影响。研究结果表明,在电流密度相同时,增大电铸液喷射流速、提高喷嘴移动扫描速度有利于获得颗粒细小、表面平整的铸层;脉冲电流、添加剂硫脲以及电铸液中加入的纳米Al2O3颗粒有助于获得平整性好的电铸层表面,其中硫脲的作用显著,能在高电流密度下抑制树枝状晶生长的形成。 (4) 采用不同工艺方法在较宽电流密度范围内制备出了具有纳米晶结构的铜电铸层,晶粒尺寸在 30~80nm之间。喷嘴移动扫描速度对铜电铸层多孔结构有明显的影响。脉冲、添加剂硫脲、纳米Al2O3颗粒能细化晶粒和提高电铸层的致密性,其中添加剂硫脲的作用最为明显。 (5) 对不同工艺条件下制备的纳米晶铜电铸层的力学性能进行了分析研究。结果表明,制备工艺条件对纳米晶铜电铸层的力学性能有较大的影响。在一定的电流密度下,直流和复合条件下制备的纳米晶铜电铸层具有较好的塑性,延伸率最高达 17%,且在塑性流变阶段没有出现应变强化现象。脉冲电流和添更多还原

【Abstract】 Rapid prototyping and nanometer-structure materials are important contents of current manufacture and material research fields. Rapid manufacturing of metal parts has become the research hot spots in the field of rapid prototyping, and it is also the one of extreme goals of rapid prototyping. The method of fabricating dimensional bulk nanocrystalline materials with high quality is one of the key technologies. Electroforming is a precision manufacturing technology in which a part is produced by the deposition of metal ions onto a pre-shaped cathode mandrel. The cathode limit current density and the deposition speed can be greatly increased, and the deposit grain sizes can be greatly refined in jet electroforming. In this paper, a new method, in which jet electroforming and rapid prototyping are integrated, is developed to fabricate metal parts directly. The fundamental experimental researches of preparing bulk nanocystalline coppers and copper parts are carried out. The major conclusions got in this dissertation are presented as follows: (1) The main factors that effect on electroforming speed are analyzed basing on the electro-deposition theory, the methods which can increase electroforming speed and refine deposit grain sizes are concluded. Based on the flow-field and electro-field of jet electroforming, the probability of rapid prototyping oriented by jet electroforming is analyzed. (2) A new technology, namely rapid prototyping oriented by jet electroforming, is brought forward, with which metal parts can be formed directly and rapidly. The device system and a pulse power are developed successfully. (3) The effects of direct current, pulse current, thiourea and nano-Al2O3 particles on the surface morphology of the copper deposits are researched systematically. The results show that fine grains and level surface of the deposits can be got by increasing electrolyte flow velocity and scanning speed of nozzle at the same current density. Using pulse current, and adding thiourea and nano-Al2O3 grains into the electrolyte are benefit for getting level deposit surfaces, and among them, the role of thiourea is the best one. (4) Nanocrystalline coppers with grain sizes in 30~80nm regime have been made in a wide rang of current density by different methods. The scanning speed of nozzle has a great effect on the pore structure of copper deposits. Using pulse current, and adding thiourea and nano-Al2O3 grains into the electrolyte can play a role in refining the grain sizes and improving the density of the copper deposits, and the role of thiourea is the best one among them, thiourea can also restrain the formation of dendrite at high current density in the course of deposition. (5) Mechanical properties of the nanocrystalline coppers fabricated by different methods are measured. The results show that the processing ways of preparing nanocrystalline coppers have great effects on the properties of the copper deposits. The coppers fabricated by direct current and composite methods have good ductilities, the elongation of the best one reaching to 17%, and no strain hardening occurs in the ductility deformation stage, the copper deposits made by using pulse current and thiourea have higher strength and micro-hardness, the maximum tensile strength of the nanocrystalline copper is about twice the one of the cold-rolled copper. The relative weight loss of nanocrystalline copper as a electode is smaller than the one of coarse-crystalline copper. (6) Electroforming speed, spot precision, thickness contribution in the deposit spots and their effects on the parts’ precision are studied. A group of nanocrystalline copper parts with good shapes and size precision, and bulk nanocrystalline coppers with the thickness in 1.1~2.0mm regime are manufactured by the rapid prototyping device.更多还原