알루미늄 합금의 TCG 조직의 형성기구

Mechanism of Twin Columnar Growth in Aluminum Alloys

Commercial semicontinuous cast ingots of aluminum alloys often exhibit large grains composed of parallel arrays of continuous lamellae. Each lamella consists of a central {111} coherent twin boundary and wavy solidification boundary. This microstructure is referred to as a twin columnar growth(TCG) structure. The factors influencing the formation of a TCG structure include a unidirectional thermal gradient and the critical range of the alloying element content. The higher the thermal gradient is, the shorter the twin plane spacings are. The composition profile for an untwinned dendrite shows maximums at the positions of the interdendritic channels and the minimum appears at the center of the dendrite. While for twinned dendrite, it has wavy apperance. This profile has two local minimums instead of one shown in the untwinned.