【作者】 葛继平；

【导师】 杨德新；

【作者基本信息】 大连交通大学 ， 材料加工工程， 2005， 博士

【摘要】 本博士学位论文研究了采用感应加热熔炼及通过旋转锻、轧制和线拉变形制备形变Cu-Fe原位复合材料的方法。用光学显微镜、SEM、TEM、XRD等实验技术对形变Cu-Fe原位复合材料的Fe纤维形成过程、立体形态及影响因素进行了系统研究和分析。结果指出,Cu-Fe铸态合金由Cu基体和α-Fe组成;在变形过程中,Fe树枝晶发生转动,平行于线轴方向排列;变形先在Fe树枝晶的一端开始,逐渐发展到整个树枝晶。中间热处理有利于Fe树枝晶变形发展成纤维。Fe纤维立体形态为弯曲的薄片状。经测定形变量在η=2.60～9.40范围内Cu相和Fe纤维厚度与形变量之间的定量关系为t=ae^-bη,a、b取决于Fe含量、原始树枝晶尺寸和中间热处理等。 用MTS测定了形变Cu-Fe原位复合材料的强度,结果指出,强度随形变量增加而提高,Fe含量高,其强度也高。强度高于混合规则计算值。分析了其强化机理,认为是界面作用的结果。强度与Cu相厚度t_Cu呈Hall-Petch关系式,可用几何协调位错强化模型和界面位错源强化模型描述。 用四点法测定了形变Cu-Fe原位复合材料的电阻率,结果发现电阻率与Fe含量、形变量和中间热处理等有关。合金Fe含量越高,形变量越大,电阻率越高。中间热处理能促进Fe从Cu基体中析出,有效地提高其导电性。分析了导电性机理,认为主要是界面散射电阻率和杂质散射电阻率的作用。Fe溶入Cu基体中导致大的杂质散射电阻率,提高导电性的核心是降低Fe在Cu基体中的溶解度。建立了电阻率和微观组织之间的关系,计算值和实验结果吻合得较好。 用SEM观察了加热过程中Fe纤维的形态变化,测定了Fe纤维断开的有关数据,并进行了数值模拟。结果指出,Fe纤维形状从片状到颗粒状变化有三种历程:直接柱状化→Rayleigh扰动;直接边缘球化;晶界分裂→柱状化→Rayleigh扰动。并分析了其计算模型,经比较,计算值和实验结果具有很好的一致性。 通过对强度和电导率的综合分析,提出了获得最佳结合的解决方案,并对进一步研究提出了建议。更多还原

【Abstract】 Deformation-processed Cu-Fe in-situ composite was manufactured by inductive melting, casting, swaging, rolling and wire drawing. Microstructural observations were carried by optical microscope, SEM, TEM and XRD. The Cu-Fe alloy consisted of Cu phase and a-Fe phase. The Fe dendrites were randomly distributed in the as-cast samples and were aligned parallel to the wire axis at the begin of deformation. During deformation the Fe phase elongated into ribbons and the microstructure refined. After small amounts of deformation the Fe morphology appeared quiet inhomogeneous, and the deformation began at the end of Fe dendrites. Atfer higher amounts of deformation the Fe ribbons had more uniform shape. The intermediate heat treatment can accelerate this process. The relationship between the thickness of Cu phase, Fe ribbons and the strain can be described by expression t=ae^-cη, and it was influenced by Fe content and intermediate heat treatment.The strength of deformation-processed Cu-Fe in-situ composite was measured by MTS. The results were shown to be anomalously higher than those predicted by rule of mixture equations. The strength increased with increasing of the deformation. However, the strength follows a Hall-Petch type relationship with the Fe ribbon spacings. The strengthening mechanism was discussed. The analysis indicated that the substructural especially phase boundary strengthening plays the crucial role. The experimental data are in good accord with the predictions of the geometrically-necessary dislocation model and interface as dislocation source model.The electrical resistivity of the composites wires was experimentally investigated by four-point measure. The electrical resistivity of these composites increased with the deformation, Fe content in alloy and Fe solubility in Cu matrix. The observed increase in resistivity with increasing wire strain is interpreted in terms of inelastic electron scattering at internal phase boundaries. Fe dissolved in the Cu matrix will make an great impurity scattering contribution to the resistivity. A series of intermediate heat treatment was done at various stages of the wire-drawn to promote precipitation of the Fe from the Cu matrix, and improved the electrical conductivity. The relationship of electrical resistivity and microstructural scales was discussed. The experimental data are in good accord with the predictions of an analytical size-effect model.The shape changes of Fe ribbons in deformation-processed Cu-Fe in-situ composite during annealing were observed by optical microscopy and SEM. The results found that the instability of Fe ribbons has three processes: direct cylinderization plus Rayleigh perturbation, edge spheroidization, longitudinal splitting plus cylinderization plus Rayleigh perturbation. The breakup kinetics of Fe filaments were monitored by quantitative metallography. Experimental results were compared with existing models and the appropriate physical model for breakup of filaments was provided.A curve of optimum tensile strength against electrical conductivity was determined. It is suggested that further improvements may be possible in Cu-Fe alloys by improved thermal mechanism processing.更多还原