The recrystallization nucleation processes of two cold-rolled Al-Mg-Si/SiCpcomposites with different contents of Mg are investigated mainly by dynamic mechanical analyzer （DMA） and electron microscopy including high angle annular dark field scanning transmission electron microscopy （HAADF-STEM） andhigh-resolution transmission electron microscopy （HRTEM）. Internal friction and electron microscopy results show that solute atom clusters are present in association with dislocationsin supersaturated cold-rolled composites. During recrystallization process, the internal friction peak position of Al-Mg-Si/3SiCp/2Mg （volume fraction,%） is higher than that of Al-Mg-Si/3SiCp（volume fraction,%） due to more solute atom clusters formed in association with the dislocations in the cold-rolled composite with a much higher Mg content, indicating a strongerresistance for the recrystallization nucleation.
Carboxymethyl starchs（CMS） with low and high degrees of substitution（CMSL and CMSH in short,respectively） were employed as depressants of diaspore in cationic reverse flotation using dodecylamine（DDA） as collector.The effect of degree of substitution of CMS on its depression performance was examined and the interaction mode and behavior were investigated in a comparative manner.Micro-flotation test showed that CMSL exhibited better performance in depressing diaspore than CMSH in a broad pH range.The adsorption of CMS on diaspore was studied by adsorption test,zeta potential measurement,and atomic force microscopy.It was found that CMSH corresponds to lower adsorption amount,thinner adsorption layer,and more negative charge than CMSL,resulting from the more chelating sites brought by the high degree of substitution.The surface tension measurement and DDA adsorption test further revealed that CMSL/DDA system gives a better depressing performance benefiting from the trapping effect by enveloping some DDA molecules inside the loop chains,while CMSH/DDA system is likely considered a quasi-surfactant.
