The squeeze casting of hypoeutectic binary Al-Cu

Abstract

A combination of thermocouple measurements, optical microscopy, and image analysis has been used to investigate the effects of applied pressure, melt temperature, mould insulation, and addition of grain refiner on the cooling/solidification behavior and resulting macro-and microstructure in squeeze cast Al-4.5 wt pct Cu ingots. Channel macrosegregates are formed in Al-4.5 wt pct Cu squeeze castings because of an increased rate of heat removal due to the application of pressure. The increased density of solute-rich liquid in the Al-Cu system causes channel segregates to form with a characteristic V pattern. Pressure and melt superheat increase the temperature gradients and cooling rate during squeeze casting but have only a minor effect upon the formation of channel segregates. The addition of grain refiner disperses but does not eliminate channel segregates. The application of pressure during squeeze casting changes the solidification behavior from mushy to near-plane front, leading to normal rather than inverse solute concentration profiles.