Hot cracking susceptibility of AlSi7MgCu alloys and effects of alloying elements magnesium and copper

Hot cracking during solidification can be a serious problem in aluminium casting alloys under certain conditions.This feature is well known,but still insuffi ciently investigated in shape casting.This study gives a brief overview of the factors inf luencing hot cracking during shape casting.Five different AlSi7MgCu alloys with varying Mg and Cu contents were examined.Theoretical models,including the cracking susceptibility coeffi cient(CSC)from Clyne and Davies,were considered.Thermodynamic calculations(terminal freezing range,TFR)of the behavior of the solid fraction during solidif ication were compared to an experimentbased hot cracking indexing(HCI)method.Scanning electron microscopy(SEM)was used to compare the existing microstructure and precipitated thermodynamic phases using the software ThermoCalc Classic(TCC).Furthermore,SEM was used to investigate crack surfaces initiated by a dog-bone shaped mold during casting.A good correlation between theoretical models and the experimental hot cracking index method was observed.