Differential thermal analysis (DTA), unidirectional solidification experiments, die casting investigations, and computational numerical simulation were conducted on commercial ADC12 alloy to evaluate the criteria conditions of the occurrence of shrinkage cavity in die casting. From the DTA analysis, the liquidus temperature of the primary alpha phase and solidification temperatures of Al-Si eutectic and multicomponent eutectic structures were identified as 856K, 838K, and 826K, respectively, which were followed by the completion of solidification at 801K. The primary dendrite phase could clearly be observed in uni-directionally solidified samples, and the relationship between the secondary dendrite arm spacing λ₂ and local solidification time ϑ_f can be expressed by the following equation. λ₂ ＝ 6.45ϑ_f^0.31 The primary dendrite phase was also seen in the die casting sample. The average cooling rate at a depth of approximately 0.5mm was 60K/s, which was calculated from the relationship between λ₂ and cooling rate. The computational numerical simulation revealed that the solidification parameter　G/√V increased just under the surface, where the shrinkage cavity could hardly be observed. The critical condition of G/√V, at which shrinkage cavity above 200μm size was seen, was 1.4 K^0.5s^0.5/mm.

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  The applicability of the permanent mold casting process for the new type of lead-free bronze with dispersed sulfide was evaluated by comparison with other conventional copper alloys, such as leaded bronze, leaded brass, and lead-free bronze containing bismuth. The copper alloys were cast into the permanent mold for the solidification cracking test. The relationship between the degree of cracking and solidification temperature range was examined.
  The new lead-free bronze with dispersed sulfide was more unbreakable than the other copper alloys. The smaller the solidification temperature range, the harder it was for solidification cracking to occur. Comparison of the new lead-free bronze with the leaded bronze and lead-free bronze containing bismuth indicated differences in the dendrite shape near the fracture and distribution of the residual melt segregated to one area towards the end of the solidification. The new lead-free bronze may also have a solidification morphology that makes it more difficult to crack, allowing it to be applied to permanent mold casting compared to other copper alloys. Its level of applicability is more or less the same as brass castings.

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