CDS technology and a 30% foundry return as shown in Ta- ble 9. The point B is well below the liquidus temperature, TL1
, predicting a good CDS process and a non-dendritic morphology of the primary phase in the as-cast microstruc- ture as confirmed by Figure 24(a).
, used for the CDS process for the three schemes in Table 10 are 7.5, 8.6 and 10, respectively. The only variable for an industry adopting to cast this alloy by CDS will be the alloy composition the parent ingot used to make Alloy 1 melt as shown by the notation “Ingot 1” in Table 10.
Examples of alloy design for CDS casting of 7075 by tilt- pour casting process with recycling schemes for foundry returns is presented in Table 10. In Table 10, three possible scenarios are presented, wherein 20%, 30% and 40% by weight of Alloy 1 are made from foundry returns from the castings of Alloy 3 (7075). In each case, the composition of Alloy 1, Alloy 2 and Alloy 3 are the same. The mass ratios, mr
Figure 26 shows a typical microstructure for Alloy 7075 cast with CDS technology (Figure 26a) and conventional technology with a 60C (108F) melt superheat for the alloy (Figure 26b). The CDS process was carried out with Alloy 1 having 30% by weight foundry returns from Alloy 3 (7075) castings. Figure 26(a) shows that the CDS process yields a non-dendritic morphology of the primary phase in the mi- crostructure whereas the morphology of the conventional cast 7075 sample in Figure 26(b) has a dendritic morphology of the primary Al phase.
Figure 27 shows typical thermal data obtained from the pour- ing cup during the tilt-pour casting of Alloy 7075 with CDS technology and a 30% foundry returns recycling scheme as shown in Table 10. Point B is well below the liquidus temperature, TL1
predicting a good CDS process and a non- dendritic morphology of the primary phase in the as-cast mi- crostructure as confirmed by Figure 26.
Table 9. CDS Process Alloy Compositions of 2024 Al Wrought Alloy with 3 Foundry Return Recycling Schemes
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International Journal of Metalcasting/Spring 11
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