Several experimental studies have b

Several experimental studies have been conducted to determine the effect of the Cu content on the susceptibility of binary Al–Cu alloys to cracking during solidification. A peak susceptibility around 1 wt.% Cu has been reported in casting, e.g., by Novikov et al. [26] and Spittle et al. [27]. As mentioned previously, the RDG model [11] was used to plot the hot cracking susceptibility HCS of binary Al–Cu alloys against their Cu contents, and a K-shaped curve was obtained with a peak near 1.4 wt.% Cu. It was mentioned by the authors that the location of the peak is sensitive to the selection of fS for the calculation of HCS [11]. A peak crack susceptibility around 1.0 wt.% Cu was calculated by Yan et al. [28] based on the model of Clyne et al. [29]. The model selected the range of0.90 < fS < 0.99 because it assumed stress relief through mass and liquid feeding in 0.40 < fS < 0.90 and grain separation in 0.90 < fS < 0.99. The ratio tV/tR was taken as the crack susceptibility, where tV is the vulnerable time period in 0.90 < fS < 0.99 and tR is the time available for stress relief in 0.40 < fS < 0.90.