Visualization of solute distributions in dendritic and spheroidized Al grains characterized by both color etching method and electron probe microanalysis

摘要

Spheroidization of Al grains was realized by compressing and partially remelting the as-received A356 aluminum alloy billets with a dendritic microstructure. A color etchant named Weck’s reagent was used to characterize the microstructures of both dendritic and spheroidal Al grains. After etching, color differences were observed inside Al grains. In the spheroidal grains, both the original dendritic structure and grain growth during water quenching were revealed by this reagent. By electron probe microanalyses, it was found that such color difference was strongly related to the microsegregation of Ti. Also, both microsegregations of Si and Ti were found in dendritic Al grains, as well as the grain growth of spheroidal Al grains during water quenching. Quantitative analyses indicated that after heating and partial remelting, the concentration of Ti was increased from dendritic grain to spheroidal grain. This phenomenon was discussed and considered to be related to Ostwald ripening and the increase of Ti solubility in Al as the temperature increased.