Ni3Al intermetallic compounds containing Cr was synthesized via Spark Plasma Sintering process. These Ni3Al intermetallic compounds containing Cr have a nearly full density after sintered at 1100 °C for 5 min under the pressure of 40MPa. Microstructure and hardness of these intermetallic compounds was studied through metallograph observation and micro hardness tests. Their formation and strengthening mechanisms were analyzed and discussed in detail. The influence of the chromium content on corrosion resistance of these intermetallic compounds was analyzed by anode polarization curves. Results show that the corrosion resistance of Ni3Al intermetallic compounds is upgraded significantly with increasing chromium content.

980MPa grade high strength low alloy steel was welded by ultra-narrow gap welding. Observed by optical metalloscope, there were large majority of equiaxial crystals in weld centers, which was the weld cross-section of 18.3%. Each weld could be compartmentalized into original microstructure zone, over heated zone and normalizing zone under next weld thermal cycle, in which the microstructures were almost the same. Through quantificational metallographic analysis, it was found there was more than 98.9% of acicular ferrite in weld metal, and other microstructures were fine. Mechanical test indicated that the strength of weld metal was higher than body material, and had outstanding plasticity. What is more, the toughness of weld metal was better than solder wire.

The ultra narrow gap welding process is suitable to the thick plate, ultra-thick plate welding with the characteristic of highly effective, high quality, low cost, low energy consumption and so on, and is easy to realize the mechanization and the automation. In this paper, the numerical simulation and technical experiment are used to study the form, grow and distribution regulation of the welding temperature field, stress field in welding joint with UNG MAW. Using the calculation to the thickness of 32mm, an example to simulate the magnitude and distribution of the residual stress in welding joint is given. Research shows that it is an effective analysis method to heat process and mechanic behavior in the welding by using finite element method numerical simulation and few experiments. Keywords: UNG MAW, Welding residual stress, Finite element method, Numerical simulation

Effect of welding heat input on the microstructure of the automatic ultra-narrow gap welded NK-HITEN610U2 steel heat affected zone (HAZ) was studied. Five heat input combinations (6kj/cm, 10kj/cm, 14kj/cm, 18kj/cm, 22kj/cm) were designated for the research. The weld joints made using these five combinations were subjected to micro-structural evaluations and hardness test for analyze the effect of the heat input on the microstructure. The results indicated that the width of heat affected zone increased with increase in the heat input.

Spark plasma sintering was used to prepare Fe-Ni (Cu-41.32wt.% Cr) alloy in order to enhance the properties as inert anode for aluminum electrolysis. The effect of different sintering processes on the microstructures and properties of Fe-Ni alloy were studied by OM, SEM and EDS. The results show that the sintering process of milled powders can be divided into three stages: particles bonding, sintering neck growing, closed pole gap becoming spherical and narrowing. The SPS process of milled powders has some advantages of reacting at lower temperatures, completing faster and being densified easier than ordinary sintering. The density of Fe-Ni sample is improved and porosity is decreased as the sintering temperature is increased and holding time is extended. 1273K and 5min are the best parameters.