this study. The liquidus temperature of Alloy 2, TL2
in
Table 5 is marginally different from that shown in Table 2. The value in Table 5 was measured in a thermal analy- sis experiment during solidification of Alloy 2 used in the casting trials and the variations in the solute concentra- tion of the alloy presented a marginal variation in the re- spective TL2
.
Table 6 presents the measured chemical compositions of the three alloys from the respective cast components from the tilt pour casting trials. The chemical compositions were measured using the Glow Discharge Optical Emission Spec- troscopy (GDOES) method.
Table 6, it could be observed that the copper content of 2024T and 7075T are higher than the nominal specified in Table 1 and this may have occurred because of the incom- plete mixing process in the pouring cup and since copper is added to Alloy 2, there may have been some left behind in the crucible containing Alloy 2 after the mixing process.
Figure 14 (a) and (b) show an example of visual inspection of a defective casting and a good sound quality casting, re- spectively. Figure 14(a) presents photographs of a defective casting obtained by the conventional casting of Al Alloy 2024 with about 60C (108F) melt superheat above the liq- uidus temperature in the tilt pour process. The conventional
casting in this photograph shows a few hot tears and crack- ing of the as-cast test bars which renders the casting unsuit- able. The same Alloy 2024 was cast in the tilt-pour casting process with the CDS technology yielding a sound cast com- ponent with no issues of hot tearing/cracking or shrinkages on the test bars as shown in Figure 14(b).
Time (s)
Figure 13. Thermal data obtained during solidification of 7075C1, 7075C2, 7075C3 and 7075CC as shown in Table 4.
Table 5. Notations, Process and Alloy Variables Used in the Tilt-Pour Casting Trials
Table 6. Compositions of Al Alloys Measured in the Cast Components in Casting Trials
International Journal of Metalcasting/Spring 11
53
Temperature (ºC)
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