铜及铜合金与钢连接技术的研究进展

本文综述了铜及铜合金与钢连接技术的国内外研究发展动态。简述了铜钢固相连接和熔化焊接领域国内外研究者已取得的部分研究成果，指出熔钎焊接工艺的发展推动了铜钢熔化焊接的应用。在工程中，须根据实际铜钢结构型式和使用条件来选择合适的焊接方法。     

Joining of HHF materials applying electroplating technology

Tungsten will be used as armor material for blanket shielding and is designated as high heat flux material for divertors, beyond application of improved W composite alloys as structural material. Independent from design (water- or helium-cooled), a successful development is inherently correlated with joining of tungsten with functional components.Depending on the design variants, the fabricated joints have to guarantee specific functional or structural properties, e.g., good thermal conductivity or mechanical load transmission. Tungsten shows lacks in adapted joining due to its metallurgical behavior ranging from immiscibility over bad wetting to brittle intermetallic phase formation. Electroplating has shown to overcome such drawbacks and that homogeneous functional (e.g., Ni or Pd) and filler (e.g., Cu) layers can be deposited.In this paper the progress achieved in development of electroplating processes for joining W to W or steel to steel will be shown. The main focus will be the characterization of the processed joints applying metallurgical investigations including SEM/EDX analyses and non-destructive testing. The mechanical stability of the produced joints is demonstrated by presenting recent shear test data. The W–W joints failed due to cracking in W, whereas the steel–steel joints cracked in the brazing zone at about 200 N/mm² load.     

Modelling the asymmetric volatility in hog prices in Taiwan: The impact of joining the WTO

Prices in the hog industry in Taiwan are determined according to an auction system. There are significant differences in hog prices before, during and after joining the World Trade Organization (WTO). The paper models growth rates and volatility in daily hog prices in Taiwan from 23 March 1999 to 30 June 2007, which enables an analysis of the effects of joining the WTO. The empirical results have significant implications for risk management and policy in the agricultural industry. The three sub-samples for the periods before, during and after joining the WTO display significantly different volatility persistence of symmetry, asymmetry and leverage, respectively.     

Reactive wetting of amorphous silica by Sn0.3Ag0.7Cu-xTi (x = 1 and 3 wt.%) alloys at 800–900 °C

The wetting of SiO₂ by molten Sn_0.3Ag_0.7Cu(SAC)-xTi (x = 1 and 3 wt.%) was studied by using the modified sessile drop method at 800–900 °C under a high vacuum. The small addition of Ti into SAC alloy can improve wettability, significantly. Because the SnTi intermetallics with high melting point covered Ti addition and blocked further dissolution of Ti, and thus Ti cannot be dissolved completely when the nominal concentration of Ti was 3 wt.%. The reaction products at liquid/solid interface are Ti₅Si₃ and TiO. The spreading dynamics can be described by reaction product control model. The spreading may be coupled firstly with the precipitation of Ti₅Si₃ and TiO together meanwhile be affected by the dissolution of Ti addition, and then the precipitation of TiO alone. The final wettability was determined both by the wetting character of reaction products and also TiO adsorption at interface.     

Vacuum brazing Mo using Ti-Ni-Nb braze alloys

A novel approach of brazing Mo using three clad Ti-Ni-Nb foils, 40Ti-35Ni-25Nb, 50Ti-35Ni-15Nb and 60Ti-15Ni-25Nb in wt.%, has been performed in the experiment. Similar microstructural evolution of the joint is observed for three foils. The joint using 60Ti-25Ni-15Nb foil brazed at 1250 °C for 600 s demonstrates the highest bending strength of 526 MPa. The clad Ti-Ni-Nb foils show potential in brazing Mo for industrial application.     

A correlation study of mechanical strength of resistance spot welding of AA5754 aluminium alloy

AA5754 aluminium alloy was resistance spot welded (RSW) to produce 27 different joint stack-ups with differing process parameters and corresponding weld quality. Quasi-static joint strength was evaluated for three test geometries; lap-shear, coach-peel and cross-tension. The results derived from over 1000 samples demonstrate various fundamental relationships. For lap-shear strength, a strong relationship with weld nugget diameter was observed; whilst discrete strength levels were found for coach-peel test geometry, depending on the governing metal thickness of the parent sheet for the various stack-ups. For cross-tension strength; there is a relationship with nugget diameter; but data are sensitive to nugget periphery defects. These fundamental relationships provide a set of generalised design guidelines for RSW of aluminium that will have significant relevance to manufacturing communities.     

The analysis of lock forming mechanism in the clinching joint

In this study, the effect of the process parameters of the clinching process on the joinability of advanced high-strength steel was investigated using finite element analysis (FEA). The effect of die geometrical parameters on the achieved joint lock size and maximum forming force has been determined. It has been determined that the die groove width is the most important parameter affecting the material flow effect and energy consumption of the joining process. From the result, the die radius, die depth, and die groove shape were mainly affected by the joinability of advanced high-strength steel H320LA.     

Brazing of Al2O3 to Ti-6Al-4V alloy with in situ synthesized TiB-whisker-reinforced active brazing alloy

65.9Cu-24.4Ti-9.7TiB₂ (wt.%) composite filler was used to join Al₂O₃ and Ti-6Al-4V alloy. 30 vol.% TiB whiskers were in situ synthesized as reinforcements in joints. Brazing temperature was 890 °C, 910 °C, 930 °C, 950 °C and 970 °C, and the holding time was 0, 5, 10, 20, and 30 min. The microstructure and mechanical properties of brazed joints were analyzed by scanning electron microscope equipped with energy dispersive spectrometer, shear test and nano-indentation test. Results show that reaction layer Ti₄(Cu,Al)₂O forms at Al₂O₃/brazing alloy interface. The reaction between TiB₂ powders and Ti atoms in brazing alloy brings on in situ synthesizing TiB whiskers in (Ti,Al)₂Cu and AlCu₂Ti intermetallics. Formation of TiB whiskers minimizes the mismatch of thermal expansion coefficient between Al₂O₃ and brazing alloy, and makes the ductile-rigid-ductile multiple layer present in joints, which reduces residual stress of joints. The maximum shear strength of joints can reach 143.3 MPa when the brazing temperature is 930 °C, and holding time is 10 min.     

SiC陶瓷与镍基高温合金的热压反应烧结连接

采用Ｔｉ－Ｎｉ－Ａｌ金属复合焊料粉末,利用Ｇｌｅｅｂｌｅ １５００热模拟机以自阻加热方式对镍基高温合金和ＳｉＣ陶瓷进行热反应烧结连接研究,获得了强度为７０ＭＰａ遥接件。微观结构分析表明铝可以通过渗透到陶瓷的非封闭孔隙中或与陶瓷发生界面反应而形成比较牢固的接头。