A357 thixoforming feedstock produced by cooling slope casting

Abstract

Cooling slope (CS) casting process was employed in the present work to produce A357 thixoforming feedstock. The dendritic primary phase in the conventionally cast A357 alloy has readily transformed into a non-dendritic one in ingots cast over a cooling plate from pouring temperatures between 620 and 640 °C and with cooling lengths between 200 and 400 mm. Dissipation of the melt superheat required longer cooling lengths for higher pouring temperatures. Primary phase in the ingots thus produced has attained a globular morphology in only as much as 5 min during isothermal holding at 580 °C. The minor effect the pouring temperature and the cooling length had on the CS-cast morphologies was not evident after reheating, implying that a wide range of CS casting parameters are capable of providing the required microstructural features for thixoforming.