PREVENTION OF MACROSEGREGATION IN SQUEEZE CASTING OF AN AL-4.5 WT PCTCU ALLOY

The squeeze casting of an Al-4.5 wt pct Cu alloy was carried out to in vestigate the conditions for the formation and the prevention of macro segregation. The effects of the process parameters, applied pressure, die temperature, pouring temperature, delay time, and humidity on the formation of macrosegregation were investigated in correlation with th e evolution of macrostructure and shrinkage defects. Two critical appl ied pressures were defined: one is the critical applied pressure, P-SC , under which shrinkage defects form, and the other is the critical ap plied pressure, P-MS, above which macrosegregates form in the squeeze castings. A quantitative diagram describing the optimum process condit ions was proposed for obtaining sound squeeze castings. It was found t hat the pouring temperature, the die temperature, the delay time, and the humidity are closely related to the two critical applied pressures P-SC and P-MS, in different manners. It was concluded that sound cast ings without macrosegregation and shrinkage defects can only be obtain ed when the applied pressure is in the range of P-SC < P < P-MS.