电磁搅拌对Cu-6%Ag合金凝固组织及硬度的影响

通过组织观察与硬度测试的方法研究了电磁搅拌对Cu-6%Ag合金凝固组织及硬度的影响。结果表明:施加电磁搅拌后,Cu-6%Ag合金的晶粒细化,初生铜枝晶变短、变粗,共晶组织细化,呈网状,铜枝晶内的银含量降低,铜枝晶的硬度由82HV升高至88HV。

拉拔变形程度和电磁搅拌对Cu-6%Ag合金组织及性能的影响

研究了拉拔变形程度和电磁搅拌对Cu-6%Ag合金组织、铜枝晶取向、抗拉强度和电导率的影响。结果表明:随着拉拔变形程度的增加,有、无电磁搅拌合金纤维状第二相的直径和间距不断减小,但合金的抗拉强度均增加,电导率均较铸态的有所下降;有电磁搅拌铸态合金的铜枝晶无取向,拉拔变形使铜枝晶的〈111〉取向增强;虽然有电磁搅拌合金中的纤维状第二相的直径和间距较无电磁搅拌合金的大,但其综合性能(强度和电导率)更优;电磁搅拌对拉拔变形后合金的抗拉强度影响不大,但却使电导率明显升高。

Influence of high magnetic field on as-cast structure of Cu-25wt.%Ag alloys

To investigate the influence of high magnetic field (HMF) on the solidification microstructure of Cu-25wt.%Ag alloy, the Cu-25wt.%Ag alloy was prepared under HMF of 12 T, and for comparison, the alloy solidified without HMF was also fabricated. Macro and microstructures of the alloys were observed using the stereomicroscope, and scanning electron microscope, field emission scanning electron microscopy. The weight percentages of the pro-eutectic and eutectic, Cu phase and Ag phase in eutectic, and precipitates of Ag phase in pro-eutectic were analyzed by using of IPP software. Results show that the morphology of the column dendrites changes into cellular dendrites and the grains are refined under HMF of 12 T. Meanwhile, the thickness of the eutectic wall increases, but the sizes of Cu phase and Ag phase and the eutectic lamellar spacings are decreased. The Ag precipitates in the Cu matrix become coarser and sparser. The weight percentage variation of the phases in the microstructure and the Cu-Ag binary phase diagram reveals that the eutectic point moves to the left of the eutectic point in the equilibrium condition and the supersaturated solid solubility of Ag decreases under HMF.

THE EFFECT OF COLD DEFORMATION ON THE KINETICS OF THE SPINODAL DECOMPOSITION OF Cu-9Ni-6Sn-0.3Ce ALLOY

By means of the measurement of mechnical properties and resistivity and X-ray diffraction and transmission microscopy,the effect of cold deformation on the kinetics of spinodal decomposition of Cu-9Ni-6Sn-0.3Ce alloy was studied.The strengthening process of the cold-worked and aged alloy was found to be accelerated.Using the theory of dislocation,the strengthening in cold-worked alloy can be attributed to the acceleration of spinodal process.

Corrosion behavior of Ce-doped Ni-10Cu-11Fe-6Al(wt%) inert anode in molten CaCl_2 salt

In this research the effect of cerium dopingon corrosion behavior of Ni-10 Cu-11 Fe-6 Al(wt%) alloy as a novel inert anode in titanium electrolytic production was investigated. The samples, including un-doped and Ce-doped nickel-based alloys, were prepared using vacuum induction melting(VIM) process and then exposed to the electrolysis in molten calcium chloride at 900C at à1.6 V versus graphite reference electrode for different immersion time. The surface and cross-section of the samples were characterized using scanning electron microscopy(SEM), and their electrochemical behavior was investigated by electrochemical impedance spectroscopy(EIS). The results show that the un-doped samples have greater number of voids and porosities as compared to that of the 0.0064 wt% Ce-doped samples(as the optimum content of cerium in the alloy). Thus, the nickel-based alloy becomes less sensitive to the pitting by addition of cerium. The corrosion penetration depth reaches about 244 mm after 16 h of electrolysis in the un-doped sample, while was approximately 103 mm for the 0.0064 wt% Ce-doped sample, which is an indication that the corrosion penetration depth decreases by adding small amounts of Ce.

Cu-Ag合金高温流变特性及其改进的本构模型

在变形温度为973~1123 K和应变速率0.01~10 s^(-1)条件下对Cu-6%Ag(质量分数)合金进行等温热压缩试验。利用试验所得流变应力-应变曲线,分析了高应变速率下Cu-6%Ag合金高温塑性变形时微观组织的演变行为;研究了高温塑性变形中材料的变形机制;构建了一种简化的本构模型,并引入Arrhenius方程及Z参数对模型进行改进。结果表明:Cu-6%Ag合金在热塑性变形过程中发生了明显的动态回复和动态再结晶;在应变速率为0.1、1及10 s-1,温度为1123 K的变形条件下发生孪生,造成流变应力突变而升高,出现应力谷值;经改进后的本构模型,考虑了应变、变形温度及变形速率对流变特性的影响,预测精度较高,更利于通过计算机语言写入有限元软件进行分析计算。