纳米Ag、Fe析出相对纤维复合Cu合金组织和性能的影响

发布时间：2018-07-03 21:51

本文选题：原位Cu基纤维复合合金 + 析出相　；参考：《浙江大学》2016年博士论文

【摘要】：本文选择Fe和Ag为能够形成原位复合第二相纤维bcc结构和fcc结构的代表性合金元素,通过直接固溶时效方法,获得了第二相以纳米级Fe,Ag粒子形式存在的Cu-6wt.% Ag和Cu-2.5 wt.% Fe二元合金；通过冷变形结合固溶时效的方法,获得了含有大量纳米级Ag-Fe复合粒子Cu-6 wt.% Fe-4 wt.% Ag三元合金,其中Cu-6 wt.% Fe合金采用相同的制备工艺,作为Cu-6 wt.% Fe-4 wt.%Ag合金的对照组。在以上初始组织的基础上,结合冷拉拔变形,研究了合金的显微结构演化,测量了强度和电阻率,分析了强化机制和电阻率散射机制。Fe析出相粒子形态在冷拉拔变形过程中基本不变,与基体不存在位相关系。Ag粒子会发生变形呈纤维状。Ag与基体保持cube-on-cube关系。这在Ag-Fe复合粒子中也成立。观察到Ag-Fe复合粒子的相界面作为位错源发射不全位错,形成层错、孪晶的过程。Cu基体中的层错不易保留而Ag相中的层错和孪晶则容易保留。形成层错和孪晶可能是Ag-Fe复合粒子中Ag相变形的重要方式之一。根据肖克莱不全位错开动的临界切应力估算Ag-Fe复合粒子三晶交接附近局域应力可达1.38GPa以上,据此推论Fe粒子变形的临界切应力在G/59以上。Ag-Fe复合粒子界面开裂,首先从Cu/Fe相界面三晶交界附近开始,然后沿着界面扩展到Ag/Fe相界面,Ag-Fe复合粒子的界面开裂可能是材料断裂的主要原因。提出了基于界面密度的强度模型,通过定义界面强化项系数k,建立界面强化项与合金具体结构的尺寸的关系,表征了尺寸效应的影响。较好地拟合了不同成分和尺寸的纤维复合合金的强度。Cu-6 wt.% Fe-4 wt.% Ag和Cu-6 wt.% Fe合金的电阻率随变形量的变化趋势基本一致,两者的差值基本等于基体中固溶Ag原子对电子散射贡献的电阻率,表明在Cu-6 wt.% Fe-4 wt.% Ag合金中,Cu/Ag相界面对Cu基体的平均自由程的影响被Cu/Fe界面的影响所覆盖。利用这个结论可以推论,在Cu-bcc体系中添加纳米Ag复合纤维能改善强度但几乎不损害电导率。
[Abstract]:In this paper, Fe and Ag are selected as representative alloy elements which can form bcc and fcc structure of in-situ composite second phase fiber. Cu-6wt.% Ag and Cu-2.5wt.% Fe binary alloys with second phase in the form of nanocrystalline Feo Ag particles are obtained by direct solution aging method. The Cu-6wt.% Fe-4wt.% Ag ternary alloy containing a large number of nano-sized Ag-Fe composite particles was obtained by the method of cold deformation and solution aging. The Cu-6wt.% Fe alloy was prepared by the same preparation process as the control group of Cu-6wt.% Fe-4 wt.%Ag alloy. On the basis of the above initial microstructure and combined with cold drawing deformation, the microstructure evolution of the alloy was studied, and the strength and resistivity of the alloy were measured. The strengthening mechanism and resistivity scattering mechanism. Fe precipitate particle morphology is basically unchanged during cold drawing deformation. The phase relation with matrix does not exist. The deformation of Ag particles is fibrous. AG has cube-on-cube relationship with matrix. This is also true in Ag-Fe composite particles. It is observed that the phase interface of Ag-Fe composite particles emits incomplete dislocation, cambium fault, and the stacking faults in Cu matrix are difficult to retain, while the stacking faults and twins in Ag phase are easy to retain. Cambium faults and twins may be one of the important deformation modes of Ag phase in Ag-Fe composite particles. According to the critical shear stress of Scholl incomplete dislocation starting, the local stress near the triple crystal junction of Ag-Fe composite particles can be estimated to be more than 1.38 GPA, and the critical shear stress of Fe particles deformed at the interface of 路Ag-Fe composite particles above G / 59 is deduced. The interface cracking of Ag-Fe composite particles at the interface of Ag / Fe phase may be the main reason for the fracture of the material, starting at the interface of Cu / Fe phase near the junction of three crystals, and then extending along the interface to the interface of the Ag / Fe phase. A strength model based on interface density is proposed. By defining the coefficient k of the interface strengthening term, the relationship between the interface strengthening term and the size of the alloy structure is established, and the effect of the size effect is characterized. The strength of fiber composite alloy with different composition and size. Cu-6wt.% Fe-4wt.% Ag and Cu-6wt.% Fe alloy have the same trend of resistivity with deformation. The difference is basically equal to the resistivity of the solid solution Ag atom in the matrix for the electron scattering. It is shown that the influence of the interface of Cu / Ag phase on the average free path of the Cu matrix in Cu-6 wt.% Fe-4wt.% Ag alloy is covered by the influence of the Cu- / Fe interface on the average free path of the Cu / Fe interface. It can be inferred from this conclusion that the addition of nano-Ag composite fibers in Cu-bcc system can improve the strength but hardly damage the electrical conductivity.
【学位授予单位】：浙江大学
【学位级别】：博士
【学位授予年份】：2016
【分类号】：TG146.11

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