Die-cast components often experience volume shrinkage during the solidification process, leading to the formation of shrinkage voids and porosity on the component's surface (see Figure 1). This issue is particularly prevalent in thick and large die-cast components. This study explores several aspects, including compensating for alloy shrinkage, preventing the formation of concentrated shrinkage voids, eliminating gas entrapment, and optimizing venting, to analyze and reduce shrinkage defects and improve the yield of die-cast components.

1. 

2. Figure 1 Shrinkage defect map
   

3. 1. Structural Improvement of Castings

Thicker walls or larger thermal junctions in castings result in more significant volume shrinkage, making it challenging to expel gases. This can lead to the formation of large shrinkage voids. To address this, it is essential to minimize thermal junctions, replace sharp angles with rounded ones, ensure uniform wall thickness, and use hollow or ribbed structures to eliminate unnecessary mass in the casting.

2. 2. Die Structure Enhancement

Increasing the cross-sectional area of the ingate prevents premature solidification and blockage of the pressure-boosting shrinkage channel. Proper design of ingate positions and flow directions helps ensure orderly filling, effective pressure transfer, and gas expulsion, reducing the likelihood of shrinkage defects.

3. 3. Process and Alloy Refinement

Enhancing the injection and pressure-filling pressures, enlarging the pressure-boosting valve opening, and optimizing the pouring temperature all contribute to improving the alloy's flow and enhancing the density of the casting structure. Careful control of alloy temperature during melting and pouring, coupled with measures to reduce pouring temperature and minimize shrinkage, can significantly impact the final casting quality.

4. 4. Operational Improvements

Ensuring consistent and sufficient feed thickness during casting is crucial for effective pressure-boosting shrinkage. Proper application of release agents and controlled drying before molding prevents excessive gas release. Attention to coating concentration, uniformity, and the use of low-release coatings contribute to minimizing gas-related defects.

5. 5. Forced Shrinkage Method

Implementing methods such as localized extrusion or forging after die casting can be an effective solution for reducing shrinkage voids. This approach involves applying external force to move liquid, semi-solid, or solid metal to compensate for volume shrinkage, improving overall casting quality.

Conclusion

Shrinkage defects in die-cast components are primarily caused by the volume contraction during alloy solidification and the entrapment of gases. Comprehensive measures, including improved casting design, optimized die structures, alloy refinement, process enhancement, and forced shrinkage methods, are necessary to effectively prevent shrinkage defects and ensure high-quality die-cast components.