REHEATING TEMPERATURE CONTRAST AND MICROSTRUCTURES OF 7075 A1 ALLOY CAST BY LIQUIDUS SEMI-CONTINUOUS CASTING

In this study, reheating of liquidus semi-continuous east billets of 7075 Al alloy wascarried out in a resistance furnace, and the temperature contrast of the outer andthe center of the reheated billets was investigated, then the reheating microstructureswere investigated. Results show that: the difference of temperature between the outerand center is small and the difference of their microstructures are also small. Dur-ing reheating at 576° C the spheroidization of grains is significant after 5rain and norosettes are visible after 20min by optical microscopy. Similar observations were madeon materials reheated at 596° C, but the ripening process is faster. The grains growup to 30-60pm, fine enough for thixoforming.