The characterization of porosity and externally solidified crystals in a high pressure die casting hypoeutectic Al-Si alloy using a newly developed ceramic shot sleeve

X.Y. Jiao ab, P.Y. Wang c, Y.X. Liu d, W.N. Liu e, A.X. Wan d, L.J. Shi c, C.G. Wang c, S.M. Xiong dShow moreAdd to MendeleyShareCite rights and content


The effective methods to regulating porosity and externally solidified crystals (ESCs) have been remained as a challenging task for high pressure die casting (HPDC) automobile parts. In this work, a newly designed ceramic shot sleeve is proposed for reducing porosity and optimizing ESCs. As a result, both porosity and ESCs achieve an effective reduction after applying the ceramic shot sleeve. This study provides insights into regulating porosity and coarse ESCs of die castings and it is expected to expand its application in industrial manufacture.


High pressure die casting (HPDC) has the advantages of high production efficiency, superior dimensional accuracy, good material utilization rate, and excellent mechanical properties [1], [2]. Thus, it has a wide range of applications in the preparation of automotive parts. Near-eutectic Al-Si alloys with high fluidity and excellent castability exhibit a satisfied strength and ductility [3], which leads to them suitable for HPDC automobile parts. However, affecting by the microstructural properties of HPDC i.e. coarse externally solidified crystals (ESCs) [4] and the gas pores, the application of HPDC parts is limited. Liu et al. [5] found the casting fracture took place preferentially at the largest pore zone which determined the final elongation. In our previous research [6], we found cracks are prone to propagate along ESCs interface, causing a trans-granular fracture mode. Therefore, decreasing large-sized pores and coarse ESCs becomes an urgent tough issue.

In recent years, vacuum-assisted HPDC has developed rapidly, leading to a significant loss of large-sized gas pores and increment of mechanical properties. We have achieved the vacuum of die cavity less than 10 kPa in the past few years. However, the shrinkages induced by the synergy of solidified contract and feeding failure are hard to remove and they become a key factor affect the performance of casting. In HPDC, the volume fraction of large-sized shrinkage is closely associated with the enrichment of ESCs [7]. High-density ESCs enriching in central region of sample develop into a large-scale ESCs dendritic framework which inhibits the feeding behavior and promotes the formation of inter-dendritic shrinkages. Thus, reducing the enrichment of ESCs is an effective method to decrease the large-sized shrinkages.

In this study, we design a newly ceramic shot sleeve for developing HPDC materials with simultaneously reducing porosity and ESCs. The evolution of porosity and ESCs in a HPDC hypoeutectic Al-Si alloy using different shot sleeve materials is discussed.

Section snippets

Materials and process parameters

A commercial hypoeutectic AlSi10MnMg is applied in this experiment and its chemical composition is the same as that in [7]. Fig. 1a shows the configuration of the experimental casting and it includes biscuit, sprue, runner, gate, overflow, standard testing bars and plate. The experimental casting is produced by a TOYO BD-350 V5 cold chamber die casting machine which is equipped with a vacuum system. The purpose of applying vacuum is to reduce porosity caused by air entrainment and the actual

Comparison of pores

Fig. 2a and b show the distribution of pores of the rod-shaped specimens fabricated by conventional steel shot sleeve and improved ceramic shot sleeve, respectively. The high-density pores concentrate in the central area of S sample (see in Fig. 2a) while the relatively diffuse pores exhibit in the C sample (see in Fig. 2b). The bounding box of 220 μm × 220 μm × 220 μm is extracted from the center of S and C sample for observing the pore characteristics (see in Fig. 2c and d). It is found that


  • (1)In HPDC process, applying ceramic shot sleeve can reduce porosity and the number of large-sized pores in a hypoeutectic AlSi10MnMg alloy.
  • (2)Compared with the HPDC sample fabricated by mold steel shot sleeve, the HPDC sample obtained by ceramic shot sleeve exhibits a lower area fraction of ESCs and more uniform microstructure.

CRediT authorship contribution statement

X.Y. Jiao: Writing – review & editing, Writing – original draft, Investigation. P.Y. Wang: Writing – review & editing. Y.X. Liu: Investigation, Data curation. W.N. Liu: Writing – review & editing. A.X. Wan: Methodology, Formal analysis. L.J. Shi: Writing – review & editing, Formal analysis. C.G. Wang: Writing – review & editing. S.M. Xiong: Writing – review & editing, Validation, Resources, Project administration, Investigation, Funding acquisition.

Declaration of competing interest

The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.


The authors would like to thank the National Key Research and Development Program of China (Grant No. 2022YFB3404201), the National Natural Science Foundation of China (Grant No.52175335) and the Fundamental Research Funds for the Central Universities (Grant No. N2302014).

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