【作者】 李鹏涛；

【导师】 严文；

【作者基本信息】 西安工业大学 ， 材料物理与化学， 2010， 硕士

【摘要】 实际中应用的细丝铜线都是由铜材经过多次拉拔得到的。即使是由OCC法制取的单晶铜线材,因初始直径较大,也需进行多次拉拔。铜线材在拉拔过程中,会产生剧烈的塑性形变,从而引起微观组织的巨大变化。单晶铜线材的初始取向对冷拔后铜线材的微观组织以及物理性能会有显著的影响。为了获得性能优良的铜线材,就要了解拉拔过程中不同初始取向对铜线材的微观组织的影响规律。本工作首先利用改进Bridgman法制取了不同初始取向的单晶铜材,再采用TEM和EBSD技术对不同初始取向经受不同变形量后单晶铜的冷拔组织进行研究,并采用维氏显微硬度计对经受不同形变量拉拔的铜线材的显微硬度进行了测量。实验结果表明,采用自行改进的高纯石墨布里奇曼改进型坩埚,在高真空条件下,温度控制在1450±5℃,在运行速度控制在2μm/s左右,可有效制备出不同取向的单晶铜试样。TEM分析结果表明,初始取向为<111>和<110>的单晶铜在真应变为0.94时,取向开始出现转动；当真应变大于0.94时,冷拔方向保持不变的微观组织特征是纵截面上位错胞沿线材的轴线方向拉长,而横截面上位错胞仍为等轴状；当真应变大于1.39时,冷拔单晶铜线材的位错胞尺寸不再随塑性变形量的增加而减小,而是达到某一个最小临界值；当真应变为1.96时,这两种取向的单晶体都有向<100>方向转动的趋势。EBSD分析结果表明,低应变下取向偏离区开始出现在试样表面。并且,随着试样真应变的增加,这样的区域逐渐由试样表面发展向试样中心区域。通过对较大真应变试样的观察表明,<111>织构较多地出现在试样中心区域,而<100>织构则是相对出现在试样表面居多。形变织构组分的稳定程度的顺序为<111>,<100>以及其它织构。在冷拔变形过程中,初始取向对形变织构的产生和分布比例有明显的影响。维氏显微硬度测试表明,未变形的<100>、<110>和<111>三种原始试样中,<110>取向的显微硬度值最大。随着真应变量的增加,初始取向为<100>和<110>单晶体显微硬度值的增加较快,当真应变大于1.96时,三种不同初始取向单晶铜试样的显微硬度值基本相同。更多还原

【Abstract】 The ultra-fine copper wires actually used in practical application can usually be obtained after being cold drawn many times. The single crystal copper wire which produced by OCC method has relatived large initial diameter, and it also needs to be drawn several times.During drawing process, the deformed microstructure will be formed and have significant influence on the microstructure and physical properties of the copper wires after cold drawing. The initial orientation of single crystal copper wires will have a significant effect on the microstructure changes and physical properties. For getting good performances of copper wires, it is necessary to know the effect of the initial orientation of single copper wires on the microstructure evolution during drawing process. In the present work, the single-crystal copper samples with different initial orientations have been prepared by use of modified Bridgman crucible,the cold drawing microstructures of the single crystal copper samples with different initial orientations after different extent deformation have been studied by TEM and EBSD method. The micro hardness is performed by Vicker hardness tester measurements.The experimental results show that with the self-improved high-purity graphite Bridgman crucible and in the high vacuum condition, if the temperature is controlled at 1450±5℃, and the running speed is controled around 2μm/s, the single crystal copper samples with different initial orientation can be effectively prepared.The TEM results show that when the strains is 0.94, the initial orientation<111> and <110>single-crystal copper starting rotation of the orientation; when the strains are larger than 0.94, there are two kinds of microstructures. First is elongated dislocation cells in the longitudinal section and the second is equiaxed dislocation in the cross section. When the strains are larger than 1.39, the size of dislocation cells decreases as the strain increasing until they reach a critical minimum size. When the strain reaches to 1.96, the single crystal samples with initial orientitation<111> and<100> will have the trend to rotation of<100> direction.The EBSD results show that at low strains, the region where the drawn direction deviate from initial orientation to other crystal directions starts to appear at the surface of the samples, and with the strains increasing, the region will spread from the surface to the center; It is observed from the serial drawing process that<111> fiber texture component parallel to the drawn direction is in the centre of the samples and<100> fiber textent compoment is in the surface. The stabilility of deformation texture components is in the order of<111>,<100>and other texture. In the cold-drawing deformation process, the initial orientation of the samples will have an evident effect on the proportion of the deformation texture generation and distribution.The Vickers hardness measurement results show that among<100>,<110> and <111>three kinds of the original sample, the sample with<110> initial orientation has the largest micro-hardness values. As the strain increases, the sample with<100>and<110> will have relatively fast increase of the Vickers hardness value. When the strains are larger than 1.96, the microhardness values of the samples with all the three initial orientation will be basically in a same level.更多还原