Next Article in Journal
Thermodynamic Modeling of Microstructural Design of Lightweight Ferritic Steels
Previous Article in Journal
Study of Microstructure, Mechanical, and Corrosion Properties of K-TIG Welded Joints of 2205/316L Dissimilar Stainless Steel
Previous Article in Special Issue
Physical Model of Liquid Steel Jets Impacting on Solid-Rigid Surfaces
 
 
Search for Articles:
Title / Keyword
Author / Affiliation / Email
Journal
Article Type
 
 
Advanced Search
 
Section
Special Issue
Volume
Issue
Number
Page
 
Journals
Metals
Volume 15
Issue 8
10.3390/met15080911
metals-logo
Submit to this Journal Review for this Journal Propose a Special Issue
► Article Menu

Article Menu

share Share announcement Help format_quote Cite
first_page
settings
Order Article Reprints
Font Type:
Arial Georgia Verdana
Font Size:
Aa Aa Aa
Line Spacing:
Column Width:
Background:
Article

Die-Casting Conditions for Pure Aluminum Heat Sink with Thin Fins

by
Hiroshi Fuse
and
Toshio Haga
*
Department of Mechanical Engineering, School of Engineering, Osaka Institute of Technology, Osaka City 535-8585, Japan
*
Author to whom correspondence should be addressed.
Metals 2025, 15(8), 911; https://doi.org/10.3390/met15080911 (registering DOI)
Submission received: 21 June 2025 / Revised: 30 July 2025 / Accepted: 15 August 2025 / Published: 16 August 2025
(This article belongs to the Special Issue Casting Alloy Design and Characterization—2nd Edition)
Browse Figures
Versions Notes

Abstract

Heat sinks with thin and tall fins made from pure aluminum using die casting are in demand due to the higher thermal conductivity of pure aluminum compared to aluminum alloys. However, die casting of thin and tall fins using pure aluminum is considered difficult because of the poor castability of pure aluminum. Casting conditions suitable for pure aluminum heat sinks with tall and thin fins were identified from flow length tests using a narrow-gap spiral die. Based on these findings, casting of pure aluminum heat sinks with thin and tall fins was attempted. The casting conditions that extended the flow length of pure aluminum were different from the conventional theoretical conditions for aluminum alloy die casting. Discovery of this unique result was very useful for the production of pure aluminum heat sinks using die casting. Specifically, using the appropriate plunger speed and die temperature to extend the flow length was effective for filling the thin fins with molten metal. As a result, it was clarified that pure aluminum heat sinks with thin and tall fins, having a height of 50 mm, a draft angle of 0.5°, and a fin top thickness of 0.5 mm, could be successfully produced using die casting. The heat dissipation properties of the pure aluminum heat sink with thin and tall fins were also evaluated.

1. Introduction

Die-cast heat sinks with high heat dissipation and light weight are in demand. Pure aluminum is considered a viable option for the production of heat sinks with high performance because it has a higher thermal conductivity than aluminum alloys. Thin fins are advantageous for reducing the weight. There are fin-type heat sinks [1,2,3,4] and pin-type heat sinks [5,6,7,8]. Simple-shaped heat sinks are usually made by forging or extrusion [9,10,11,12,13] using wrought aluminum alloys, as the flow stress for wrought aluminum alloys is small, making them suitable for plastic forming [14,15,16]. Pure aluminum also has low flow stress, and pure aluminum heat sinks with fins are thus typically also manufactured by forging or extrusion. However, heat sinks with complex shapes cannot be made using these methods.
Die casting of aluminum alloys is suitable for making complex-shaped heat sinks. However, die casting is generally not appropriate for pure aluminum, especially products with thin walls, such as heat sink fins, because the molten metal flow tends to stop, and the walls (fins) may not be completely filled. The castability of the pure aluminum is poor compared to aluminum alloys for die casting like A383. There are few reports or products of pure aluminum heat sinks with thin fins made by die casting. Current die-cast fin-type heat sinks are limited to fins with low height [17].
Casting conditions that influence castability have been investigated. The effects of plunger speed [18,19], die temperature [18,19,20], and molten metal temperature [21,22] on the flow length were investigated. The flow length increased as the plunger speed, die temperature, and molten metal temperature increased in conventional die casting. However, in these studies, dies with a narrow gap (e.g., 0.5 mm) were not used, and it is unclear whether their results are applicable to products cast using such dies.
It is empirically known that filling thin fins with pure molten aluminum is difficult. Appropriate plunger speeds and die temperature conditions for casting heat sinks with thin and tall fins have not been clearly identified. It was predicted that casting conditions that extend the flow length could enable die casting of pure aluminum heat sinks with thin fins. In the present study, casting conditions that influence the fluidity of pure aluminum were investigated using a spiral die with a narrow gap. Heat sinks with thin and tall fins were cast using the conditions that achieved longer flow lengths in the die.
Pure aluminum heat sinks with a fin top thickness of 0.5 mm, a fin height of 50 mm, and a draft angle of 0.5° could be successfully cast using the casting conditions obtained from flow length tests with the narrow-gap spiral die. Thin and tall fins could be completely filled by the pure aluminum. The appropriate plunger speed and die temperature were found to be different from those typically considered appropriate based on conventional die-casting theory. In this paper, it is shown that die casting can be used to produce pure aluminum heat sinks with thin and tall fins by applying the appropriate plunger speed and die temperature identified in fluidity tests using the narrow-gap spiral die. The relationship between casting conditions and fluidity is also clarified. Additionally, the heat dissipation performance of the die-cast pure aluminum heat sink with thin and tall fins is compared to that of a heat sink cast from aluminum alloy for die casting.
Die-cast pure aluminum heat sinks are assumed to be primarily used for ceiling lights. Casting conditions generally affect the microstructure, porosity, and strength. However, the microstructure and porosity of the die-cast heat sinks were found not to strongly influence heat dissipation [23]. Additionally, strength is not required for ceiling light heat sinks. Therefore, in this study, evaluation of the pure aluminum heat sinks was based only on the filling of the thin and tall fins.

2. Experimental Methods

A 500 kN cold chamber die-casting machine (HC 50F, Hishinuma Machinery, Ranzan Town, Saitama Prefecture, Japan) with an injection power of 100 kN and a sleeve diameter of 45 mm was used in the present study [24]. The die temperature was set using a mold temperature controller (TT28, Hishinuma Machinery, Ranzan Town, Saitama Prefecture, Japan) [25]. The chemical compositions of the pure aluminum, JIS ADC12 [26], and Al-25%Si, as measured by an emission analyzer (PDA-5500, Shimadzu Co,. Kuwaharamachi, Nishinokyo, Chukyouku, Kyoto city, Kyoto Prefecture, Japan), are summarized in Table 1. The chemical compositions of the cast specimens were not checked. The aluminum was melted in an oxidizing atmosphere using a gas furnace. Various types of dies have been used for fluidity tests in previous studies [22,27,28,29], with the spiral die being most common among them. A spiral die was therefore used in the present study to investigate fluidity, as illustrated schematically in Figure 1 [30]. The width of the die channel was 7 mm, and the channel gap was set to 0.5 mm. A crimp was placed at the tip of the spiral test piece for the fluidity tests, beyond which the channel gap was not filled by the molten metal. The crimp and unfilled area were not considered part of the flow path [30]. Only portions of the path with a rectangular cross-section were measured to determine the flow path length.
To examine the effects of the plunger speed and die temperature on the flow length, plunger speeds of 0.2, 0.4, 0.6, and 0.8 m/s, and die temperatures of 30, 70, 110, and 150 °C [31] were used. The die temperature was measured using thermocouple at five points in the die gap, and the temperature variation was within 10 °C. The molten metal temperature was 720 °C [30]. To examine the effect of the molten metal temperature, pouring temperatures of 720 and 780 °C were used, with plunger speeds of 0.2, 0.4, 0.6, and 0.8 m/s and a die temperature of 30 °C. Although 780 °C is too high for practical use, it was chosen to investigate the effect of a higher molten metal temperature on the flow length. Ten test pieces were cast under each condition. Microstructures were observed by optical microscopy (VHX-900, Keyence Co., Higashi Nakajima, Yodogawa Ku, Osaka City, Osaka Prefecture, Japan).
The shape and name of each part of the heat sink are shown in Figure 2. An overview of the four-finned heat sink and its parts is shown in Figure 2a. The heat sinks used for filling tests had either four or six fins. The dimensions of these heat sinks are shown in Figure 2b,c. The fin top thickness, fin height, and fin draft angle were 0.5 mm, 50 mm, and 0.5°, respectively. The base thickness was 2 mm. This shape was chosen to cast a heat sink with tall and thin fins compared to conventional heat sinks using pure aluminum. In previous research, a heat sink with this shape could be cast using Al-25%Si, which has excellent fluidity [23]. The die temperature and molten metal temperature were same as those used for the flow length test. The plunger speed for casting pure aluminum heat sinks was determined based on the flow length test results and volume conversion of molten metal flow areas in the heat sinks, as described in Section 3.3.1. The casting conditions for the fin filling tests are summarized in Table 2. Ten test pieces were cast under each condition.
The casting conditions are expected to influence the porosity and microstructure in the heat sinks. However, it has been shown that heat dissipation is not affected by the porosity or microstructure of heat sinks [23]. Additionally, high mechanical strength is not required for ceiling light heat sinks. Therefore, in this study, the castability of pure aluminum heat sinks with thin and tall fins was evaluated based on molten metal filling into the fins. Al-25%Si has excellent fluidity and is suitable for casting heat sinks with thin and tall fins [23]. The filling conditions for the fin and molten metal flow in the fin were compared between Al-25%Si and pure aluminum. The Al-25%Si heat sink was cast using the mold shown in Figure 2b. The die temperature was 150 °C, the plunger speed was 1.6 m/s, and the molten metal pouring temperature was 790 °C. These conditions were selected based on previous research.
The thermal conductivity of pure aluminum is greater than that of JIS ADC12 (which is comparable to A383), an aluminum alloy often used for die casting. The heat dissipation properties of pure aluminum and ADC12 heat sinks were compared.
The heat sinks used to investigate the heat dissipation performance are shown in Figure 2d,e. Figure 2d shows the dimensions for the pure aluminum heat sink, and Figure 2e shows the dimensions for the pure aluminum and ADC12 heat sinks. The heat sink dimensions in Figure 2e are similar to those of a conventional ADC12 heat sink. The fin top thickness and fin draft angle for the Figure 2d heat sink were determined based on the results of the casting test shown in Figure 2b. The fin height and base thickness were the same for the two heat sinks in Figure 2d,e, while the fin top thickness and fin draft angle were different. For the heat sink in Figure 2d, the fin top thickness and fin draft angle were 0.5 mm and 0.5°, and the base thickness was 4 mm. For the heat sink in Figure 2e, the fin height was 50 mm, the fin top thickness was 1 mm, the fin draft angle was 1°, and the base thickness was 4 mm. The fin height and the base thickness in Figure 2e were kept the same in order to investigate the influence of thermal conductivity on heat dissipation, as these factors influence the heat dissipation performance [23]. The weights of the heat sinks and thin fin weight reduction were investigated by comparing the heat sinks of Figure 2d,e.
A schematic illustration of the experimental apparatus for investigating heat dissipation is shown in Figure 2f,g. The mounting method for the heater, thermocouple, detector and aluminum sheet is shown in Figure 2f. The equipment to maintain temperature uniformity is shown in Figure 2g. A square-shaped micro-ceramic heater (MS-3, Sakaguchi, Akihabara, Tokyo, Japan) measuring 10 mm on each side was attached to the back of the heat sink and operated at 40 W. A DC stabilized power supply (PSF-400L2, Texio, Yokohama City, Kanagawa Prefecture, Japan) was used to heat the micro-ceramic heater. A 0.5-mm-thick thermal interface material sheet (EX20000C7, Dexerials, Shimotsuke City, Tochigi Prefecture, Japan) was inserted between the heat sink and the micro-ceramic heater. The temperature of the micro-ceramic heater, defined as that 30 min after saturation, was measured using a T-type thermocouple. The temperatures of the as-cast and black-body heat sinks, the dimensions of which are shown in Figure 2d,e, were measured three times each. A black spray was applied for the black-body heat sink. The casting conditions for the heat dissipation tests are summarized in Table 3.

3. Results and Discussion

3.1. Effect of Plunger Speed, Die Temperature, and Molten Metal Temperature on the Flow Length of Pure Aluminum

The effects of the plunger speed and die temperature on the flow length of pure aluminum are shown in Figure 3. When the die temperature was 30 °C, the flow length decreased as the plunger speed increased. In contrast, when the die temperature was higher than 70 °C, the flow length increased as the plunger speed increased. The effect of the plunger speed on the flow length at a die temperature of 30 °C was different from that higher than 70 °C. The relationship between the plunger speed and the flow length at 30 °C is different from that expected from conventional theory, which states that the flow length increases as the plunger speed increases [18,19,20,21,22,23,24,25,26]. This result was very unique. At a die temperature higher than 70 °C, the flow length appeared to saturate at a plunger speed of 0.6 m/s, while at 30 °C, it is predicted that the flow length could slightly increase at plunger speeds less than 0.2 m/s.
The longest flow lengths of pure aluminum at each die temperature are compared in Figure 4a, shown as a ratio relative to the flow length at a die temperature of 30 °C and a plunger speed of 0.2 m/s. When the die temperature was 30 °C, the flow length was longest at a plunger speed of 0.2 m/s. When the die temperature was higher than 70 °C, the flow length was longest at a plunger speed of 0.8 m/s, and increased slightly as the die temperature increased. However, the longest flow length at 30 °C was about 20% greater than that at any die temperature higher than 70 °C. Notably, the flow length at a die temperature of 30 °C and a plunger speed of 0.2 m/s was longer than that at a die temperature of 150 °C and a plunger speed of 0.8 m/s. These findings indicate that with a die gap of 0.5 mm, the flow length can be extended at a lower die temperature and lower plunger speed, which differs from the prediction of conventional theory [18,20].
It is predicted that the molten metal speed decreases as the distance from the gate increases. Flow lengths under various die temperatures and a plunger speed of 0.2 m/s are compared in Figure 4b, and the results are again shown as a ratio relative to the flow length at 30 °C. When the die temperature was 30 °C, the flow length was longest. When the die temperature was higher than 70 °C, the flow length was not influenced by the die temperature and was almost the same. The longest flow length at a die temperature of 30 °C was about 50% greater than that at die temperatures higher than 70 °C. When the die temperature was higher than 70 °C, the flow length decreased as the molten metal flow speed decreased. When the die temperature was 30 °C, Figure 3a suggests that the flow length may increase as the molten metal flow speed decreases below 0.2 m/s. Therefore, a die temperature of 30 °C and a plunger speed of 0.2 m/s may be suitable for die casting heat sinks with thin and tall fins.
The effect of the molten metal temperature and the plunger speed at a die temperature of 30 °C on the flow length of pure aluminum is shown in Figure 5. The flow length was longer at a molten metal temperature of 780 °C than at 720 °C. The tendency of decreasing flow length with increasing plunger speed was not influenced by the molten metal temperature. The difference in flow length between molten metal temperatures of 720 °C and 780 °C at a plunger speed of 0.2 m/s was smaller than at other plunger speeds. It is predicted that the flow length gradually increases as the plunger speed decreases below 0.2 m/s at a molten metal temperature of 780 °C. The flow length may also gradually increase at a plunger speed lower than 0.2 m/s and a molten metal temperature of 720 °C. However, the flow length at 720 °C may not be longer than that at 780 °C at a plunger speed lower than 0.2 m/s. This is because the flow length at 780 °C is almost saturated, and the flow length at 720 °C may be saturated at a plunger speed lower than 0.2 m/s. The difference in flow length between 720 and 780 °C may be small when the plunger speed is lower than 0.2 m/s. However, the lowest plunger speed for the die-casting machine used in this study was 0.2 m/s, and flow lengths at speeds lower than 0.2 m/s could not be investigated. When the die gap for the spiral die was 0.5 mm, appropriate casting conditions for achieving a longer flow length were as follows: a plunger speed of 0.2 m/s, a die temperature of 30 °C, and a molten metal temperature of 780 °C. When the plunger speed was 0.2 m/s and the die temperature was 30 °C, the flow length at a molten metal temperature of 720 °C was about 92% of that at 780 °C, which can be considered a small difference.

3.2. Microstructure of Flow-Length Test Piece of Pure Aluminum Cast Using Spiral Die

Cross-sectional microstructures of the flow-length test pieces of pure aluminum are shown in Figure 6. α-Al was refined in pure aluminum. In Figure 6a, the die temperature was 30 °C and plunger speed was 0.2 m/s; in Figure 6b, the die temperature was 150 °C and plunger speed was 0.2 m/s. The molten metal temperature was 780 °C in both cases. The observation point was 50 mm from the gate. The grain size in Figure 6a was larger than that in Figure 6b, despite the higher die temperature in Figure 6b. It is predicted that the contact between the molten metal and the die surface in Figure 6a was poorer than in Figure 6b, resulting in lower heat transfer. Consequently, the grain size in Figure 6a was larger. The surface of the test piece in contact with the die also appeared more uneven in Figure 6a than that in Figure 6b, possibly due to a gap between the solidified layer and the die surface. In Figure 6a, there are pores on the surface of the flow-length test piece, and these pores are thought to be hindering heat transfer to the die.
The cross-section shown in Figure 6a supports the interpretation from the previous study [32] that the solidified layer peels away from the die surface due to heat shrinkage. The predicted solidification processes of pure aluminum are schematically shown in Figure 7 [30]. Figure 7a corresponds to the cross-section in Figure 6a. When the die temperature was 30 °C and plunger speed was 0.2 m/s, the solidified layer peeled from the die surface as shown in Figure 7a(A4), reducing heat transfer from the solidified layer to the die and slowing the cooling of the molten metal inside the layer. This increases the solidification time and results in a longer flow length. When the die temperature was 180 °C and plunger speed was 0.2 m/s, peeling did not occur before solidification completed, as shown in Figure 7b, or peeling occurred at a higher solid fraction than in the case of Figure 6a, resulting in higher heat transfer between the solidified layer and the die. The heat transfer between the solidified layer and the die surface in Figure 6b is larger than that after peeling in Figure 6a, and is the cause of the shorter flow length.

3.3. Casting of Heat Sink

3.3.1. Consideration of Plunger Speed

Al-25%Si has excellent fluidity, allowing heat sinks with thin and tall fins like that in Figure 2b to be cast [23,32]. In this study, heat sinks of this shape were cast using Al-25%Si for two purposes: first, to estimate the appropriate plunger speed for casting pure aluminum heat sinks by matching the molten metal speed in the fins; and second, to compare molten metal flow and filling between Al-25%Si and pure aluminum.
A side view of the Al-25%Si heat sink and the predicted molten metal flow are shown in Figure 8. The size of this heat sink is shown in Figure 2b. The flow remained on the sides of the fins, as shown in Figure 8a, and the predicted molten metal flow is shown in Figure 8b. The width of the molten metal flow in the fin was about 20 mm. The plunger speed for casting the heat sink was based on the molten metal flow at a width of 20 mm and a fin thickness of 0.5 mm. Under these conditions, the plunger speed that makes the molten metal speed in the fin the same as that in the channel of the spiral die at a plunger speed of 0.2 m/s and a molten metal temperature of 780 °C was predicted to be 2.3 m/s for the heat sink with four fins and 3.4 m/s for the heat sink with six fins. However, the maximum plunger speed for the die-casting machine was 1.6 m/s, which was lower than the above predicted speeds. A plunger speed of 1.6 m/s corresponds to equivalent spiral die plunger speeds of 0.14 m/s and 0.1 m/s for the four- and six-finned heat sinks, respectively. Judging from Figure 3a, which depicts the results of the flow length tests of pure aluminum using the spiral die at a temperature of 30 °C, the flow length at plunger speeds of 0.1 and 0.14 m/s may be sufficient because it is predicted that the flow length increases slightly when the plunger speed is below 0.2 m/s. The heat sink of pure aluminum was thus cast at a plunger speed of 1.6 m/s. Die temperatures of 30 and 150 °C and molten metal temperatures of 720 and 780 °C were used for casting the heat sinks, and these conditions were the same as those used in the flow length tests.
The dominant casting conditions influencing the flow length were the plunger speed and the die temperature, judging from the results of the flow length test of pure aluminum. For casting the heat sinks of pure aluminum, the plunger speed was fixed at 1.6 m/s, which was deemed appropriate based on the results of the spiral die flow length test of pure aluminum when the die temperature was 30 °C, as described above. The effects of the die temperature and molten metal temperature on the filling of the fin by molten metal of pure aluminum was then evaluated. It is notable that appropriate casting conditions for heat sinks of pure aluminum with thin fins can be predicted from the results of flow length tests using a spiral die with a narrow gap.

3.3.2. Casting of Pure Aluminum Heat Sink

The fin filling results are summarized in Table 4. Photographs of the four- and six-finned pure aluminum heat sinks are shown in Figure 9. At a die temperature of 30 °C and a plunger speed of 1.6 m/s, the fin tops for the four-finned and six-finned heat sinks were fully filled with pure aluminum. The molten metal temperature did not influence filling at the fin tops, as shown in Figure 9a,b. Figure 5 shows that the difference in flow length between molten metal temperatures of 720 and 780 °C was small when the plunger speed was 0.2 m/s. The difference in flow length may also be small at plunger speeds lower than 0.2 m/s. The difference in filling of the fin top between molten metal temperatures of 720 and 780 °C was also very small. Thus, a plunger speed of 1.6 m/s and a die temperature of 30 °C were appropriate casting conditions for the four-finned and six-finned heat sinks. For these heat sinks, the number of fins did not greatly influence filling at the fin tops. In contrast, when the die temperature was 150 °C and the plunger speed was 1.6 m/s, unfilled fin tops were observed, as shown in Figure 9c,e. These results show that a die temperature of 150 °C was not appropriate for casting the heat sinks. In Figure 4, when the die temperature was 150 °C, the flow length was the shortest at a plunger speed of 0.2 m/s. At a plunger speed lower than 0.2 m/s and a die temperature of 30 °C, the fin tops could be filled successfully, while a die temperature of 150 °C resulted in unfilled fin tops. These findings demonstrate that fin top filling in heat sink casting can be predicted from the results of flow length tests.
In conventional die-casting theory, the flow length is expected to increase as the die temperature and plunger speed increase. This theory applies to the die casting of general products having a thickness of about 3 mm, and suggests that when both the die temperature and plunger speed are low, molds cannot be completely filled by molten metal. However, for die casting of pure aluminum using a die with a narrow gap (e.g., 0.5 mm), the conventional theory is not applicable. The present study demonstrates that a low plunger speed and die temperature are appropriate for casting pure aluminum products with thin walls (e.g., 0.5 mm).
Side views of pure aluminum heat sinks cast under conditions A2 and A3 (Table 4) are shown in Figure 10a,b, respectively, along with predicted molten metal flow patterns. In A2, shown in Figure 10a, the fin tops were fully filled with no cracking occurring, and the flow pattern resembled that for Al-25%Si (Figure 5). This means that under condition A2, the flowability of pure aluminum was better, comparable to that for Al-25%Si, and the heat sink could be successfully cast. In A3, cracks and unfilled areas appeared near the fin tops. In the gray area of the schematic illustration of Figure 10b, the molten metal temperature and the flow speed might have decreased, stopping the flow. This may have caused the pressure to drop and the solid fraction to increase, leading to the occurrence of defects. After flow stopped in the gray area, molten metal may have entered from the side of that area, as shown in the schematic.
Porosity existed in flow-length test pieces of Figure 6, and surface defects like wrinkles and flow lines existed in heat sinks of Figure 9 and Figure 10. A cause of these defects may be the low castability of pure aluminum. An increase of casting pressure may be useful to improve these defects [33,34].

3.4. Heat Dissipation Properties of Pure Aluminum Heat Sink

The heat dissipation properties of as-cast and black-body pure aluminum and ADC12 heat sinks [35] were compared. The dimensions of the heat sinks are shown in Figure 2d,e, and the casting conditions are summarized in Table 3. The heat sinks listed in Table 3 could be cast without defects. Heater temperatures were measured as an indicator of heat dissipation properties using the method shown in Figure 2f,g, and the results are shown in Figure 11. The heater temperatures for both the as-cast and black-body pure aluminum heat sinks cast under conditions C1 and C2 in Table 3 were lower than those for the ADC12 heat sinks cast under condition C3 in Table 3. This is due to the thermal conductivity of pure aluminum being greater than that of ADC12 [36,37]. The heater temperatures for the pure aluminum heat sinks for conditions C1 and C2 with the dimensions in Figure 2d,e were almost the same as those shown in Figure 11a,b. This result indicates that the fin thickness did not remarkably influence heat dissipation [23]. Adopting pure aluminum for heat sinks is useful for improving the heat dissipation performance.
The weights of heat sinks cast under conditions C1, C2, and C3 are shown in Figure 12. C1 and C2 were pure aluminum, and C3 was ADC12. C1 corresponds to the dimensions in Figure 2d, while C2 and C3 correspond to Figure 2e. The heat sink shown in Figure 2d was approximately 25% lighter than the conventional heat sink shown in Figure 2e. Pure aluminum heat sinks with thin and tall fins (C1) therefore have the dual advantages of good heat dissipation performance and reduced weight.

4. Conclusions

The effects of plunger speed, die temperature, and molten metal temperature on the flow length of pure aluminum in a narrow die gap were investigated in order to enable die casting of pure aluminum heat sinks with thin and tall fins. Contrary to conventional theory, which states that the flow length increases as the plunger speed and the die temperature increase, the results in the present study reveal that the appropriate conditions for achieving long flow lengths are a lower plunger speed and die temperature. Additionally, the effect of the molten metal temperature on the flow length could be neglected when the plunger speed and the die temperature were appropriately selected. This is the first noteworthy result of this study. The longer flow length achieved when the die gap was narrow and the die temperature and plunger speed were lower may have resulted from peeling of the solidified layer from the die surface, which was confirmed by microstructure observations.
Die casting of pure aluminum heat sinks with thin and tall fins was successfully carried out using casting conditions identified by flow length tests with a narrow channel gap. Pure aluminum heat sinks with a fin top thickness of 0.5 mm, a fin height of 50 mm, and a fin draft angle of 0.5° could be cast using suitable casting conditions for achieving a long flow length. These fins are much thinner and taller than could be previously cast when using pure aluminum. This is the second noteworthy result of this study. The appropriate plunger speed and die temperature for casting these heat sinks also contradicted conventional theory, demonstrating that predictions based on flow length tests using narrow gaps are effective for casting pure aluminum heat sinks with thin and tall fins. This is the third noteworthy result of this research. Additionally, the present study confirms that pure aluminum heat sinks with thin and tall fins have excellent heat dissipation and reduced weight compared to conventionally shaped ADC12 and pure aluminum heat sinks.

Author Contributions

Conceptualization, H.F. and T.H.; methodology, H.F. and T.H.; validation, H.F. and T.H.; formal analysis, H.F. and T.H.; investigation, H.F. and T.H.; resources, H.F. and T.H.; data curation, H.F. and T.H.; writing—original draft preparation, H.F. and T.H.; writing—review and editing, H.F. and T.H.; visualization, H.F. and T.H.; supervision, T.H.; project administration, T.H.; funding acquisition, H.F. All authors have read and agreed to the published version of the manuscript.

Funding

This research was supported by the Adaptable and Seamless Technology Transfer Program through Target-Driven R&D Feasibility Study Stage Exploratory Research (JPMJTM20Q5) from the Japan Science and Technology Agency (JST).

Institutional Review Board Statement

Not applicable.

Informed Consent Statement

The original contributions presented in the study are included in the article; further inquiries can be directed to the corresponding author.

Data Availability Statement

The original contributions presented in the study are included in the article, further inquiries can be directed to the corresponding author.

Conflicts of Interest

The authors declare no conflicts of interest.

References

  1. Jain, Y.; Kurkute, V.; Deshmikh, S.M.; Pathan, H.A.; Attar, A.R.; Kahn, S.A. The influence of plate fin heat sink orientation under natural convection on thermal performance: An experimental and numerical study. J. Adv. Res. Fluid Mech. Therm. Sci. 2024, 114, 118–129. [Google Scholar] [CrossRef]
  2. Rasangika, A.H.D.K.; Nasif, M.S.; Pap, W.; Al-Waked, R. Effect of fin spacing on the vibration-assistant thermal performance of heat sink. IOP Conf. Ser.-Earth Environ. Sci. 2023, 1281, 012059. [Google Scholar] [CrossRef]
  3. Mani, P.; Radhakrishnan, S.; Mahalingam, A.; Vellaiyan, S. Heat dissipation effects of different nanocoated lateral fins an experimental investigation. Therm. Sci. 2024, 28, 293–305. [Google Scholar] [CrossRef]
  4. Grochalski, K.; Rukat, W.; Jakubek, B.; Wieczorowaki, M.; Słowiński, M.; Sarbinowska, K.; Graboń, W. The influence of geometry, surface texture, and cooling method on the efficiency of heat dissipation through the heat sink-A Review. Materials 2023, 16, 5348. [Google Scholar] [CrossRef]
  5. Li, Y.; Wang, T.; Wang, Z.; Ahu, C.; Yang, J.; Yang, B. Thermal-hydraulic performance analysis of combed heat sink with open microchannels and embedded pin fins. Energies 2024, 17, 5301. [Google Scholar] [CrossRef]
  6. Heidarshenas, B.; Abidi, A.; Sajadi, S.M.; Tuan, Y.; EI-Shafay, A.S.; Aybar, H.Ş. Numerical study and optimization of thermal efficiency for a pin fin heat sink with nanofluid flow by modifying flow by modifying heatsink geometry. Case Stud. Therm. Eng. 2024, 55, 104125. [Google Scholar] [CrossRef]
  7. Wang, J.; Qi, S.; Xu, Z.; Xu, X. Experimental investigation of the thermal-hydraulic characteristics of liquid cooling heat sinks with novel pin fins. Case Stud. Therm. Eng. 2024, 55, 104172. [Google Scholar] [CrossRef]
  8. Sadi, T.; Sijan, A.R.; Shifa, F.H.M.; Haque, M.R.; Harun-Or-Rashid, M. Numerical investigation of effect of perforated almond. tunnel, and bishop shaped pin fin heat sinks on the hydrothermal performance enhancement. Int. J. Thermofluids 2024, 23, 100727. [Google Scholar] [CrossRef]
  9. Mallikarjuna, V.; Rajesh, K.; Ramesh, K.; Reddy, B.R.B. Modeling and Optimization of shape of a Heat Sink Fins on Motherboard. J. Comput. Math. Sci. 2015, 65, 228–251. [Google Scholar]
  10. Durgam, S.; Ghodake, B.; Mohite, S. Numerical investigation on heat sink material for temperature control of electronics. J. Phys. Conf. Ser. 2022, 2312, 012016. [Google Scholar] [CrossRef]
  11. Pujol, T.; T’Jollyn, I.; Massaguer, E.; Massaguer, A.; Cózar, I. Design optimization of plate-fin heat sink with forced convection for single-module thermoelectric generator. Appl. Therm. Eng. 2023, 221, 119866. [Google Scholar] [CrossRef]
  12. Fischer, T.; Bissoonauth, C.; Liang, H.; Bai, J. Enabling cross-morphological performance comparison: A case study in heat management design. Mater. Des. 2024, 239, 112826. [Google Scholar] [CrossRef]
  13. Kumar, A.; Sharma, P.K.; Roy, P.K. Effect and analysis of die angle on stress distribution during aluminum rod extrusion process. J. Comput. Technol. 2023, 12, 1–8. [Google Scholar]
  14. Górecki, K.; Posobkiewicz, K. Cooling systems of power semiconductor devices-a review. Energies 2022, 15, 4566. [Google Scholar] [CrossRef]
  15. Czerwinski, F. Aluminum alloys for electrical engineering: A review. J. Mater. Sci. 2024, 59, 14847–14892. [Google Scholar] [CrossRef]
  16. Available online: https://myheatsinks.com/why-pire-aluminum/ (accessed on 25 February 2025).
  17. Available online: https://www.tokyo-kouatsu.jp/product/heatsink.html (accessed on 25 February 2025).
  18. Komazaki, T.; Asada, J.; Watanabe, K.; Sasaki, H.; Nishi, N. Effects of Casting Conditions on Flow Length of Thin-Walled Diecasting for ADC 10 Alloy. Imono 1995, 67, 689–695. [Google Scholar]
  19. Hga, T.; Imamuea, S.; Fuse, H. Fluidity Investigation of Pure Al and Al-Si Alloys. Materials 2021, 14, 5372. [Google Scholar] [CrossRef] [PubMed]
  20. Asan, Y.E.; Ҫolak, M. Modeling the effect of pour height, casting and mold heating conditions for the analysis of fluidity of different section thickness in die mold casting of Al12Si alloy. J. Sci. Technol. 2022, 15, 14–27. [Google Scholar] [CrossRef]
  21. Timelli, G.; Bonollo, F. Fluidity of aluminium die castings alloy. Int. J. Cast Met. Res. 2007, 20, 304–311. [Google Scholar] [CrossRef]
  22. Chen, G.C.; Li, X. Effect of TiC nano-treating on the fluidity and solidification behavior of aluminum alloy 6063. J. Mater. Process. Technol. 2024, 324, 118241. [Google Scholar] [CrossRef]
  23. Haga, T.; Fuse, H. Die Casting of Lightweight Thin Fin Heat Sink Using Al-25%Si. Metals 2024, 14, 622. [Google Scholar] [CrossRef]
  24. Available online: https://hishinuma.jp/menu/2013/09/hc50f.html (accessed on 29 January 2025).
  25. Available online: https://hishinuma.jp/menu/cat/cat132/cat1/ (accessed on 29 January 2025).
  26. Japan Industrial Standard (JIS) H 5202; Aluminum Alloy Die Castings. Japanese Standards Association: Tokyo, Japan, 2010.
  27. Han, Z.; Wang, Z.; Sun, Z.; Zhang, B.; Rao, W. Influence of non-uniform ultrasonic vibration on casting fluidity of liquid aluminum alloy. Res. Dev. 2022, 19, 380–386. [Google Scholar] [CrossRef]
  28. Zhang, G.; Wang, Z.; Niu, J.; Xu, H.; Ren, X. Enhanced Fluidity of ZL205A Alloy with the Combined Addition of Al-Ti-C and La. Materials 2021, 14, 6169. [Google Scholar] [CrossRef]
  29. Zou, G.; Chai, Y.; Shen, Q.; Cheng, T.; Zhang, H. Analysis of the Fluidity and Hot Tearing Susceptibility of AlSi3.5Mg0.5Cu0.4 and A356 aluminum alloys. Int. J. Metalcast. 2022, 16, 909–923. [Google Scholar] [CrossRef]
  30. Haga, T.; Fuse, H. Fluidity of Pure Aluminum in a Narrow Channel Die Gap during Die Casting. Metals 2024, 14, 1133. [Google Scholar] [CrossRef]
  31. Aoyama, S.; Akase, M.; Sakamoto, K. Evaluation of lubricant film deposit on die casting die surface by measuring glossiness. J. Jpn. Inst. Light Met. 1991, 41, 49–54. [Google Scholar] [CrossRef]
  32. Haga, T.; Fuse, H.; Terao, M. Fabrication thin heat sink by the die casting of semisolid Al-25%Si. Solid State Phenom. 2018, 285, 423–428. [Google Scholar] [CrossRef]
  33. Costanza, G.; Quadrini, F.; Tata, E. Pressure effect on Al alloy cast behaviour: Microstructures and mechanical properties. Int. J. Mater. Prod. Technol. 2004, 20, 345–357. [Google Scholar] [CrossRef]
  34. Abe, Y. Die-casting machine. J. Jpn. Inst. Light Met. 2019, 69, 512–517. [Google Scholar] [CrossRef]
  35. Fuse, H.; Imamura, S.; Terao, M.; Haga, T. Semisolid die casting of hypereutectic Al-25%ssSi alloy. Mater. Trans. 2020, 61, 993–999. [Google Scholar] [CrossRef]
  36. Available online: https://group.nikkeikin.co.jp/act/technology/basic.html (accessed on 25 February 2025).
  37. Available online: https://www.diecasting.or.jp/diecast/pdf/book/pdf_set023-0.pdf (accessed on 25 February 2025).
Metals 15 00911 g001
Figure 1. Schematic illustration of spiral die. (a) Shape; (b) dimensions. Units: mm. Reprinted from [19].
Figure 1. Schematic illustration of spiral die. (a) Shape; (b) dimensions. Units: mm. Reprinted from [19].
Metals 15 00911 g001
Metals 15 00911 g002
Figure 2. Schematic diagram of the heat sinks and apparatus for measuring heat dissipation properties. (a) Overview of the four-finned heat sink; (b,c) dimensions of the four- and six-finned heat sinks used for the casting test (fin filling test); (d,e) dimensions of the heat sinks used for heat dissipation tests; (f,g) apparatus for measuring heat dissipation properties; (f) position of heat sink, heater, and thermocouple; (g) equipment to maintain temperature uniformity.
Figure 2. Schematic diagram of the heat sinks and apparatus for measuring heat dissipation properties. (a) Overview of the four-finned heat sink; (b,c) dimensions of the four- and six-finned heat sinks used for the casting test (fin filling test); (d,e) dimensions of the heat sinks used for heat dissipation tests; (f,g) apparatus for measuring heat dissipation properties; (f) position of heat sink, heater, and thermocouple; (g) equipment to maintain temperature uniformity.
Metals 15 00911 g002
Metals 15 00911 g003
Figure 3. Effects of die temperature and plunger speed on the flow length of pure aluminum. Die temperature: (a) 30 °C, (b) 70 °C, (c) 110 °C, (d) 150 °C.
Figure 3. Effects of die temperature and plunger speed on the flow length of pure aluminum. Die temperature: (a) 30 °C, (b) 70 °C, (c) 110 °C, (d) 150 °C.
Metals 15 00911 g003
Metals 15 00911 g004
Figure 4. Effects of die temperature and plunger speed on the flow length of pure aluminum. (a) Ratio of the longest flow length at each die temperature to the flow length at a die temperature of 30 °C and plunger speed of 0.2 m/s. When the die temperature was 70, 110, and 150 °C, the flow length was longest when the plunger speed was 0.8 m/s. (b) Ratio of the flow length at each die temperature to the flow length at a die temperature of 30 °C. The plunger speed was 0.2 m/s.
Figure 4. Effects of die temperature and plunger speed on the flow length of pure aluminum. (a) Ratio of the longest flow length at each die temperature to the flow length at a die temperature of 30 °C and plunger speed of 0.2 m/s. When the die temperature was 70, 110, and 150 °C, the flow length was longest when the plunger speed was 0.8 m/s. (b) Ratio of the flow length at each die temperature to the flow length at a die temperature of 30 °C. The plunger speed was 0.2 m/s.
Metals 15 00911 g004
Metals 15 00911 g005
Figure 5. Effects of the molten metal temperature and plunger speed on the flow length of pure aluminum. Die temperature: 30 °C. T: molten metal temperature. The errors bars represent the standard deviation.
Figure 5. Effects of the molten metal temperature and plunger speed on the flow length of pure aluminum. Die temperature: 30 °C. T: molten metal temperature. The errors bars represent the standard deviation.
Metals 15 00911 g005
Metals 15 00911 g006
Figure 6. Cross-sections of specimens for the flow length test of pure aluminum. (a) Die temperature: 30 °C, plunger speed: 0.2 m/s; (b) die temperature: 150 °C, plunger speed: 0.2 m/s.
Figure 6. Cross-sections of specimens for the flow length test of pure aluminum. (a) Die temperature: 30 °C, plunger speed: 0.2 m/s; (b) die temperature: 150 °C, plunger speed: 0.2 m/s.
Metals 15 00911 g006
Metals 15 00911 g007
Figure 7. Schematic illustration of the effect of die temperature on the solidification of pure aluminum molten metal. (a) Die temperature: 30 °C, plunger speed: 0.2 m/s (Figure 6a); (b) die temperature: 150 °C, plunger speed: 0.2 m/s (Figure 6b).
Figure 7. Schematic illustration of the effect of die temperature on the solidification of pure aluminum molten metal. (a) Die temperature: 30 °C, plunger speed: 0.2 m/s (Figure 6a); (b) die temperature: 150 °C, plunger speed: 0.2 m/s (Figure 6b).
Metals 15 00911 g007
Metals 15 00911 g008
Figure 8. Side view of Al-25%Si four-finned heat sink (dimensions shown in Figure 2b) and predicted metal flow in the fins. (a) Side view of the heat sink. (b) Predicted molten metal flow in fins.
Figure 8. Side view of Al-25%Si four-finned heat sink (dimensions shown in Figure 2b) and predicted metal flow in the fins. (a) Side view of the heat sink. (b) Predicted molten metal flow in fins.
Metals 15 00911 g008
Metals 15 00911 g009
Figure 9. Four-finned and six-finned pure aluminum heat sinks. Casting conditions in (a–e) are A1, A2, A3, B1, and B2, respectively, and these are summarized in Table 2. (a,b,d) are free from defects. Arrows in (c,e) show a crack and an unfilled area. (a–c) are four-finned heat sinks, and (d,e) are six-finned.
Figure 9. Four-finned and six-finned pure aluminum heat sinks. Casting conditions in (a–e) are A1, A2, A3, B1, and B2, respectively, and these are summarized in Table 2. (a,b,d) are free from defects. Arrows in (c,e) show a crack and an unfilled area. (a–c) are four-finned heat sinks, and (d,e) are six-finned.
Metals 15 00911 g009
Metals 15 00911 g010
Figure 10. Side views of pure aluminum heat sinks cast under conditions A2 and A3, as in Table 4. (a) A2; (b) A3. Heat sink shapes are shown in Figure 2b. Schematics show the predicted molten metal flow pattern.
Figure 10. Side views of pure aluminum heat sinks cast under conditions A2 and A3, as in Table 4. (a) A2; (b) A3. Heat sink shapes are shown in Figure 2b. Schematics show the predicted molten metal flow pattern.
Metals 15 00911 g010
Metals 15 00911 g011
Figure 11. Heater temperature measured using the method depicted in Figure 4. (a) As-cast body; (b) black body. Casting conditions C1, C2, and C3 are listed in Table 3. C1 and C2 are pure aluminum and C3 is ADC12.
Figure 11. Heater temperature measured using the method depicted in Figure 4. (a) As-cast body; (b) black body. Casting conditions C1, C2, and C3 are listed in Table 3. C1 and C2 are pure aluminum and C3 is ADC12.
Metals 15 00911 g011
Metals 15 00911 g012
Figure 12. Weights of heat sinks cast by the conditions C1, C2, and C3 listed in Table 3. C1 and C2 are pure aluminum, and C3 is ADC12.
Figure 12. Weights of heat sinks cast by the conditions C1, C2, and C3 listed in Table 3. C1 and C2 are pure aluminum, and C3 is ADC12.
Metals 15 00911 g012
Table 1. Chemical compositions of pure aluminum and aluminum alloys (mass%).
Table 1. Chemical compositions of pure aluminum and aluminum alloys (mass%).
MaterialCuSiMgFeZnMnTiBal.
Pure Al0.000.040.000.100.030.000.00Al
JIS ADC121.9210.310.280.790.810.310.04Al
Al-25%Si1.6224.180.220.630.380.340.03Al
Table 2. Casting conditions for pure aluminum for heat sinks.
Table 2. Casting conditions for pure aluminum for heat sinks.
ConditionHeat Sinks Shown in Figure 2Number of FinsPlunger Speed
(m/s)		Die Temperature (°C)Pouring Temperature of Molten Metal (°C)
A1Figure 2b41.630720
A2Figure 2b41.630780
A3Figure 2b41.6150780
B1Figure 2b61.630720
B2Figure 2b61.6150780
Table 3. Casting conditions for heat sinks for the investigation of heat dissipation.
Table 3. Casting conditions for heat sinks for the investigation of heat dissipation.
ConditionHeat Sinks Shown in Figure 2MaterialPlunger Speed (m/s)Die Temperature (°C)Pouring Temperature of Molten Metal (°C)
C1Figure 2dPure Al1.630780
C2Figure 2ePure Al1.630780
C3Figure 2eADC121.6150720
Table 4. Effects of casting conditions on fin filling of pure aluminum heat sinks.
Table 4. Effects of casting conditions on fin filling of pure aluminum heat sinks.
TypeHeat Sinks Shown in Figure 2Filling of Fins
A1Figure 2bYes
A2Figure 2bYes
A3Figure 2bNo
B1Figure 2cYes
B2Figure 2cNo
Disclaimer/Publisher’s Note: The statements, opinions and data contained in all publications are solely those of the individual author(s) and contributor(s) and not of MDPI and/or the editor(s). MDPI and/or the editor(s) disclaim responsibility for any injury to people or property resulting from any ideas, methods, instructions or products referred to in the content.

Share and Cite

MDPI and ACS Style

Fuse, H.; Haga, T. Die-Casting Conditions for Pure Aluminum Heat Sink with Thin Fins. Metals 2025, 15, 911. https://doi.org/10.3390/met15080911

AMA Style

Fuse H, Haga T. Die-Casting Conditions for Pure Aluminum Heat Sink with Thin Fins. Metals. 2025; 15(8):911. https://doi.org/10.3390/met15080911

Chicago/Turabian Style

Fuse, Hiroshi, and Toshio Haga. 2025. "Die-Casting Conditions for Pure Aluminum Heat Sink with Thin Fins" Metals 15, no. 8: 911. https://doi.org/10.3390/met15080911

APA Style

Fuse, H., & Haga, T. (2025). Die-Casting Conditions for Pure Aluminum Heat Sink with Thin Fins. Metals, 15(8), 911. https://doi.org/10.3390/met15080911

Note that from the first issue of 2016, this journal uses article numbers instead of page numbers. See further details here.

Article Metrics

Back to TopTop