【作者】 邓鉴棋；

【导师】 叶以富；

【作者基本信息】 华东理工大学 ， 材料学， 2010， 博士

【摘要】 科学技术和现代工业的迅猛发展,对铜基复合材料的强度性能和导电性能都提出了更高要求。本文通过热力学分析、参考已有研究工作以及实际生产的可行性,设计并制备了有可能实现高强度和高电导性相匹配的Cu-10Cr-XZr(X=0、0.2、0.4、0.6)系复合材料。利用ABAQUS6.5软件对强烈塑性变形(拉拔和累积叠轧)制备Cu-10Cr-XZr(X=0、0.2、0.4、0.6)系复合材料的工艺过程进行了有限元模拟,采用金相显微镜、扫描电子显微镜、透射电子显微镜、X射线衍射仪等分析手段,系统深入地研究了该复合材料棒材的基体以及增强纤维的组织演变过程,分析了Zr含量、变形应变以及退火温度对棒材强度和电导率的影响,并讨论了累积叠轧工艺对Cu-Cr-Zr系复合材料板材的显微组织、力学电学性能、表面织构以及结合强度的影响,探索了大塑性变形下Cu/Cr界面扩散原理以及Cr纤维高温失效模型。得出以下结论：(1)模拟结果表明拉拔过程中产生的塑性变形不均匀,弹性变形或者塑性变形主要靠近拉拔试样表面。拉拔速率的增大,减小了最大等效应力,但对等效应变影响不大。摩擦系数对于拉拔变形中总能量具有较大影响。当摩擦系数介于0～0.1时,变形中的总能量增幅较小。而当摩擦系数增大到0.1以后,随着摩擦系数的增大,变形中总能量的数值迅速增加。(2)模拟发现累积叠轧工艺过程中产生的塑性变形比较均匀,只有在轧辊接入部位存在少量应力集中。但是随着变形量的增大,在轧辊接入部位的网格出现了严重的压缩和拉伸,应力应变分布也有不均匀的现象,若在实际实验中则容易出现应力集中,导致裂纹产生。此外还发现单道次制备变形量为75%板材时出现轧制无法进行的情况。在实际实验中应尽量避免单道次变形量≥75%的叠轧。(3)微量合金元素Zr的添加,能够细化Cr相,在Cu-10Cr-0.4Zr和Cu-10Cr-0.6Zr合金中没有发现典型的Cr树枝晶。Cu-10Cr-XZr(X=0、0.2、0.4、0.6)四种合金铸态下Cr相的平均宽度分别为15.8μm、14.4μm、6.3μm和4.7μm。大塑性变形后,较细小的Cr相比粗大的Cr更易生成均匀细小的纤维。当变形应变为6.2时,Cu-10Cr形变复合材料平均纤维厚度为0.5～1μm,而Cu-10Cr-0.4Zr形变复合材料平均纤维厚度可达250nm左右。(4) Cu-10Cr-XZr(X=0、0.2、0.4、0.6)系形变复合材料在冷拉拔过程中,Cr相在纵向主要经历以下四个阶段：自由取向→扁化和旋转→搭接与合并→均匀化；而在横向,Cr主要经历的阶段包括：自由取向→扁化和旋转→弯曲与扭折→不规则化。(5) Cu-10Cr-0.4Zr形变复合材料的纤维厚度D与变形应变η可由式D=9.77396exp(-2.8η)表示。纤维厚度与Cu-10Cr-XZr(X=0、0.2、0.4、0.6)系形变复合材料的强度为分段式函数关系：当η<4.2,强度增量为：当η≥4.2时,强度增量为：应用上述模型计算得到的材料强度与实测值基本吻合。(6)根据退火过程中Cr相纤维的热稳定性研究提出Cu-Cr-Zr形变复合材料高温纤维的失稳模型—纤维诱导迁移合并机制。该模型认为Cr纤维的失稳过程主要包括：次生纤维粘附于主纤维表面、次生纤维团聚球化、进一步团聚球化并向边界移动、次生纤维球体与主纤维边缘合并以及主纤维发生柱状化转变五个阶段。Cu-10Cr-XZr(X=0、0.2、0.4、0.6)形变复合材料Cu基体中阻碍晶界迁移的阻力主要来源于三部分：纤维Cr/Cu相界面阻碍、形变织构阻碍以及孪晶界阻碍。(7)在单道次下,形变量为50%、55%、60%、65%和70%时,复合材料结合界面特征与纯金属材料结合界面特征有较大差异。在变形量为50%时,复合材料结合界面由Cu基体组成。当变形量增加到55%时,结合界面由Cu基体和增强相共同组成。变形量增加到60%以上时,结合界面变得平直,结合效果较好。层间结合力测试表明：当变形量增加到60%～70%以后,材料的最大结合力提高到600N以上,故单道次下对Cu-10Cr-0.4Zr复合材料进行累积叠轧处理的最佳变形量应该为60%左右。更多还原

【Abstract】 With the rapid development of the science and technology, and modern industry, the copper-based composites must have higher strength and higher electrical conductivity. In this paper, it has been used that the thermodynamic calculation, finite element simulation, and relevant studies to design and prepare a low cost Cu-10Cr-XZr (X= 0,0.2,0.4,0.6) wires and plates with high-strength and high conductivity. The processes of severe plastic deformation (including drawing and accumulative roll-bonding (ARB)) were simulated and analyzed by using software ABAQUS6.5. It was studied that microstructural evolution and mechanical properties of the matirx and reinforced fibers, the influence of strengthening and toughening phase with Zr contents on the microstructures and properties of the composites, the effect of accumulative roll-bonding (ARB) on microstructure, mechanical properties, electrical properties, surface texture, and the bonding strength, the interface diffusion principle and failure model of Cr fiber at high temperature with optical microscopy, scanning electron-microscopy (SEM), transmission electro-microscope (TEM) and X-ray diffraction (XRD). The conclusions were obtained as follows:(1) The results of the finite element simulation of drawing process showed that the plastic deformation was inhomogeneous, elastic deformation or plastic deformation rounded in the drawing-link surface in the process of drawing. With the increasing of drawing rates, the maximum equivalent stress reducesd, but only a little influence affected on the equivalent strain. The friction coefficient had a larger influence on the total energy of deformation. When the friction coefficient was 0～0.1, the total energy increasing would decrease during deformation. And when the friction coefficient increased to more than 0.1, with increasing of the friction coefficient increases, the value of the total energy would raise increasing rapidly during deformation.(2) The results of the finite element simulation of ARB process showed that ARB process would produce a uniform plastic deformation all over tha sample, and only a little stress centration in the parts of accessing to the roller. But as the deformation increased, the grid would have some serious compression and tension in the parts of accessing to the roller, the distribution of stress and strain would have extremely un-uniform. It would be easily to create stress concentration in the experiment, resulting in cracks. In addition, it also found that the process of one-pass with deformation of 75% would not complete, which should be avoided in the actual experiment.(3) The addition of Zr could refine the Cr phases. In Cu-10Cr-0.4Zr and Cu-10Cr-0.6Zr alloys, the typical Cr dendrites could not be found. The average width of Cr phases were 15.8μm,14.4μm,6.3μm and 4.7μm individually in Cu-10Cr-XZr (X= 0,0.2,0.4,0.6). After a large plastic deformation, the thinner and smaller Cr phases would generate small and homogeneous fibers more easily than the thicker and larger Cr phases. When the strain ratio reached 6.2, the average width of Cr in Cu-10Cr would be about 0.5μm～1μm, and in the Cu-10Cr-0.4Zr composite, the average width be about 250nm.(4) During the cold drawing process, Cr fibers in Cu-10Cr-XZr (X= 0,0.2,0.4,0.6) composites at the vertical sections contained the following four main steps:free orienting→rotating and thinning→overlapping and merging→homogenizing; but at the horizontal sections contained four different steps:free orienting→rotating and thinning→bending, twisting and folding→irregul arizing.(5) Between fiber thickness D and deformation ratioη, there was a relationship in the composite Cu-10Cr-0.4Zr:D=9.77396 exp(-2.8η). In the composites Cu-10Cr-XZr(X=0、0.2、0.4、0.6), there were piecewise functions between the strength and fiber thickness:whenη<4.2, the Incremental of strength could be expressed as and whenη≧ 4.2, The calculated values by this model had a good agreement with the experimental values.(6) The failure process of stability about Cr fibers in the aging process included five steps:secondary fibers adhibitting to the surface of the primary fibers, spheroidizing of secondary fibers, further spheroidizing of secondary fibers and the spheroid moving to the boundary, spheroid of secondary fibers combining with the edge of the main fibers, column transitting. Which was the model of the failure process of stability about high-temperature fibers in the deformation composite Cu-Cr-Zr—fiber-induced mechanism of migration and merge. There were three kinds of resistances to prevent migration of grain boundaries in the Cu matrix:obstruction from the Cr/Cu phase interfaces, deformation textures and twin boundaries(7) The interface features of composites and the pure metals in the ARB processes were quite different. Under the deformation ratio of 50%, the interfaces of Cu-Cr-Zr composites were composed of Cu matrix; when the deformation ratio increased to 55%, the interfaces composed of Cu matrix and Cr phases; and when the deformation ratio increased to 60%, the combination of interfaces become straight. The interlayer bonding tests showed that:if the deformation ratios increased to 60%～70%, the maximum bonding stress would be more than 600N, so the best deformation ratio 60% of one-pass ARB was recommened in Cu-Cr-Zr composites.更多还原