Effect of pouring temperature on microstructure and microsegregation of as-cast aluminum alloy

摘要

An experimental investigation of pouring temperature effects on the thermal parameters, microstructure, and microsegregation during directional solidification of the hypoeutectic Al-Cu alloy is presented and discussed. The hypoeutectic Al-4.0 wt.% Cu alloy with superheat temperature is poured at temperatures 682.5, 747.5, and 812.5 degrees C. The thermal parameters (cooling rate, solidification speed, and local solidification time) are affected by pouring temperature. These, in turn, affects the microstructure arrangement and microsegregation profiles. Experimental growth laws of tertiary dendrite arm spacing relating to the cooling rate have been determined, indicating that increase in thermal parameter was responsible for the refinement effect on dendritic morphology. Results showed that pouring temperatures nearer to the liquidus temperature produced a dendritic array refined, i.e., pouring temperatures few degrees Celsius higher than the liquidus temperature favored the reduction of the tertiary dendrite arm spacings. The results of chemical composition obtained by fluorescence X-ray spectrometry technique confirmed that microsegregation profiles were influenced by pouring temperature, i.e., the microsegregation profiles were shown to move upward with the decrease in the pouring temperature.