China Foundry (Jul 2013)
Hot cracking susceptibility of AlSi7MgCu alloys and effects of alloying elements magnesium and copper
Abstract
Hot cracking during solidification can be a serious problem in aluminium casting alloys under certain conditions. This feature is well known, but still insufficiently investigated in shape casting. This study gives a brief overview of the factors influencing hot cracking during shape casting. Five different AlSi7MgCu alloys with varying Mg and Cu contents were examined. Theoretical models, including the cracking susceptibility coefficient (CSC) from Clyne and Davies, were considered. Thermodynamic calculations (terminal freezing range, TFR) of the behavior of the solid fraction during solidification were compared to an experiment-based 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.
