the wedge while a large riser (114 mm diameter, 356 mm height) was located at the opposite end. The wedge mould was made of resin bonded zirconium sand and had a foam filter (10 ppi) placed at the ingate to collect any oxide films. The pouring times were kept between 14 to 16 seconds to ensure consistent filling between each wedge casting.
The total metal poured to make a wedge casting was ap- proximately 22.7 kg. After the wedge castings were com- pletely solidified, the sand was mechanically removed and the rigging cut from the wedge as indicated in Figure 7. Each wedge casting weighed approximately 8.2 kg after the riser, downsprue and gating system were removed.
Figure 5. The first derivative curve and the calculated baseline curve for the Al-7wt%Si- 4wt%Cu alloy. The three peaks in the figure correspond, from left to right, 1) primary α-Al dendritic growth, 2) Al-Si eutectic growth, and 3) Cu-based multi-phase eutectics.20
Figure 6. Cast wedge is shown with rigging. The location of three K-type thermocouples along with cooling rates is indicated. The 15 mm slices cut for metallography are also indicated.
International Journal of Metalcasting/Fall 10 37
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