The process of vacuum electron beam welding is characterized by deep-penetration with the action of keyhole effect. The assumption of simple cylindrical physical model of keyhole is reasonable according to the thermal transfer of the keyhole effect during welding. There is an intensive evaporation arises from the front keyhole wall owing to the high energy density of electron beam. Therefore, an analysis model of heat transfer at the interface of vapor phase and front keyhole wall was proposed to the temperature calculation on the basis of heat transfer theory. The evaporation of the primary elements, which are Mg, Al, Zn and Mn in AZ series magnesium alloy, can be analyzed by the model, as well as the influence of keyhole radius varying on the temperature at vapor-solid interface offront keyhole wall. And dimensionless parameters are introduced to analyze the influence of the process condition on the thermal effect. The calculation results show that Mg and Zn are vulnerable to vaporize loss during the vacuum electron beam welding on AZ series magnesium alloy, and the evaporation of Mg occurs earlier than Zn. A longer electron beam acting duration and smaller keyhole size will increase the temperature of the front keyhole wall significantly, which has a considerable influence on the evaporation effect of the elements.

Modeling of resistance spot welding process on galvanized steel sheet was investigated. Mathematical models developed by nonlinear multiple regression analysis and artificial neural network approach were employed in the prediction of welding quality factors, namely nugget diameter, penetration rate and tensile shear strength, under some welding conditions. According to the prediction models on quality, the prediction systems of welding process parameters were formulated respectively on the basis of Newton-Raphson iterative algorithm and cascade forward back propagation algorithm in order to obtain the desired welding quality. The results showed that the prediction precision of cascade forward back propagation algorithm was higher than Newton-Raphson iterative algorithm. The current duration had the largest prediction error, followed by electrode force and welding current. Therefore, it was concluded that the current duration was the most difficult parameter in prediction system of welding process in order to obtain the desired welding quality.

By the method of adding MNP (micron or nano particles) into general solder, the composite electronic solder can be prepared, due to its role of solution or dispersion strengthening, and can improve the thermostable fatigue and creep properties of solder joint, it is also usually named as RCS (reinforced composite solder).Based on researchful analysis of RCS, such as metal particles, particles for high hardness, particles for low expansion coefficient, rare-earth particles and low aggregated particle, and of their reinforced mechanism, the technical requirements of RCS is found, it is also analyzed problems and application prospects of RCS.

Due to increase refined lead production and slow industrialization of lead-free solders, hazard of lead to human and environment still existed. Based on pollutions of lead depending on the volatility and the solubility of lead, the new ways to prevent and reduce the pollution of lead were put forward. The lead content in lead-solders could be reduced appropriately and the dense surface film could be formed by micro-alloying in the view of material for reducing the pollution. Low soldering temperature and the optimal soldering process or equipment could also be taken to reduce the pollution of lead.

The semi-solid brazing process of SiCp/A356 composites and aluminum alloy was investigated. The two substrates were heated up to the semisolid temperature range of Zn-Al filler metal in the joint region by a resistance heating plate. At this point a stirrer was introduced into the weld seam in order to mix filler metal and the two sides of substrates into a single uniform joint. After stirring, specimens were sectioned for analysis of macro- and micro-structures along the weld region. The research shows that SiCp/A356 composites and aluminum can be successfully joining with semi-solid filler metal. It can be found that most of the oxide film on the surface of the base metal was disrupted and removed through the observation by SEM. The metallurgical bonds formed between the filler metal and the base materials. Moreover, the oxide film of surface of aluminum alloy was more thoroughly disrupted and removed than that of surface of composites with existing of Sic particle. The joint microstructure with globular α-Al grain enclosed by rich-Zn phase can be obtained after stirring brazing.