STRAIN-INDUCED MACROSEGREGATION IN SQUEEZE CAST AL-MG AND AL-SI ALLOYS

Compact components of Al-Mg and Al-Si alloys have been squeeze cast at different pressures to give strain induced macrosegregation. The macr osegregation has been determined by chemical analyses over the cross s ection of the casting. Secondary dendrite arm spacing, DAS, and grain size have been measured near the edge and in the central area of the c ross section. For the Al-Si alloys, macrosegregation located close to the hot spot was found in all dense squeeze castings, and the segregat ion was more significant as the Si-content decreased. Only a small amo unt of macrosegregation located close to the hot spot was observed in squeeze cast Al-Mg alloys. Low alloy wrought alloys were determined to be more sensitive to strain induced macrosegregation than foundry all oys. Generally, the segregation tendency increased with increasing pre ssure and decreasing alloying content, and decreased with increasing g rain size when the pressure is sufficiently high.