In this paper, the kinetics of pressure leaching for purification of metallurgical grade silicon with hydrochloric acid was investigated. The effects of particle size, temperature, total pressure, and concentration of hydrochloric acid on the kinetics and mechanism of iron removal were studied. It was found that the reaction kinetic model followed the shrinking core model, and the apparent activation energy of the leaching reaction was 46.908 kJ/mol. And the apparent reaction order of iron removal with pressure leaching was 0.899. The kinetic equation was obtained and the mathematical model of iron removal from metallurgical grade silicon (MG-Si)

Vertical material flow and microstructure evolution were investigated by the material tracing technology during friction stir lap welding of 6061-T6 aluminium alloys from a new perspective: various angles of keyhole obtained by emergency stop technique. First, lamellar grains were transformed into equiaxed subgrains, and texture was transitioned from 110//shear direction fibre texture to strong B/ B components when materials flowed from the advancing side to the leading side. Then subgrains grew into recrystallised grains at the retreating side. After that the downward material flow at the trailing side induced plastic deformation, resulting in many subgrains with strong A/ Ā texture components. Finally, grains grew up and retained with strong A/ Ā components in the stir zone.

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