Structures with dissimilar materials can make full use of the advantages of each material. However the welding of the aluminum alloy plate and plastic plate are difficult due to high difference in melting point. The friction stir lap welding method is selected in this paper. The numerical model was built to study the heat transfer behavior inside the plates, as the temperature plays an important role in determine the weld quality. The model was validated through experimentally measured temperature results. The influence of welding process parameters such as welding speed, tool rotating speed and downward feed was analyzed. It was found that under the welding speed of 100r/min and downward feed of 0.3mm/s, sound weld was produced.

In order to improve the flowability of lithium hydroxide powder, the lithium hydroxide powder in a company was selected under the conveying condition. The degree of circularity was used to quantitatively characterize the micro-morphology of the powder, and the influence of particle size on the flowability of lithium hydroxide powder was studied by the angle of repose method, HR method and Carr flowability index method. The results show that the lithium hydroxide powder gets better with the increasing of particle size. But the flowability of fine particles (≤ 100μm) is poor, while the flowability of medium particles (100~200μm) and coarse particles (≥ 200μm) is good. Based on the experimental results. It is suggested that the inclination angle of silo should be designed to be no less than 500 and the content of powder with particle size less than 100μm in lithium hydroxide should be controlled to improve the conveying efficiency of lithium hydroxide powder.