Study on the Effect of Casting Pressure on the Wear Resistance of Al-Si Alloy Prepared by Squeeze Casting

Boosting Al-Si Alloy Performance: How Squeeze Casting Pressure Unlocks Superior Wear Resistance

This technical summary is based on the academic paper "Study on the Effect of Casting Pressure on the Wear Resistance of Al-Si Alloy Prepared by Squeeze Casting" by Muna Khedier Abbass and Osama Sultan Muhammed, published in JKAU: Eng. Sci. (2012). It has been analyzed and summarized for technical experts by CASTMAN.

Keywords

• Primary Keyword: Squeeze Casting Pressure
• Secondary Keywords: Al-Si Alloy, Wear Resistance, High Pressure Die Casting, Microstructure Refinement, Porosity Reduction, Mechanical Properties

Executive Summary

• The Challenge: Improving the wear resistance and mechanical properties of Al-Si alloys beyond what is achievable with traditional gravity die casting.
• The Method: An Al-12%Si alloy was prepared using squeeze casting at various pressures (7.5 to 53 MPa) and compared to a gravity-cast sample.
• The Key Breakthrough: Increasing squeeze pressure up to 53 MPa significantly refines the microstructure, boosts hardness by over 70% (from 69 to 118 VHN), and decreases the wear rate.
• The Bottom Line: Applying higher pressure during solidification is a critical lever for reducing porosity and enhancing the durability of Al-Si components.

The Challenge: Why This Research Matters for HPDC Professionals

For decades, engineers have sought to enhance the performance of aluminum alloys for critical applications, from automotive wheels to aerospace components. Squeeze casting, a process that combines casting and forging principles, has emerged as a superior method for producing high-integrity parts. While its benefits are known, a deeper understanding of how process parameters—specifically applied pressure—directly influence the final material properties is crucial for optimizing manufacturing. This research addresses the need to quantify the relationship between Squeeze Casting Pressure and the resulting microstructure, hardness, and wear resistance of Al-Si alloys, providing a data-driven roadmap for producing more durable and reliable components.

The Approach: Unpacking the Methodology

The researchers conducted a comparative study using a eutectic Al-Si alloy (AlSi12) known for its excellent castability.

• Materials: The study used an Al-12%Si alloy. The chemical composition is detailed in Table 1 of the paper.
• Casting Processes:
  • Gravity Die Casting: As a baseline, the alloy was melted at 700°C and poured into a metallic mold preheated to 200°C.
  • Squeeze Casting: The same alloy was poured into a preheated (200°C) die on a vertical hydraulic press. A constant ram speed of 25 cm/min was used to apply pressures of 7.5, 23, 38, and 53 MPa for 30 seconds during solidification.
• Analysis & Testing: The resulting samples were evaluated for:
  • Microstructure: Examined after grinding, polishing, and etching.
  • Hardness: Measured using a Vickers hardness tester (VHN) with a 300 mg load for 15 seconds.
  • Density & Porosity: Calculated based on weight and volume measurements.
  • Wear Resistance: Assessed using a Pin-On-Disc wear apparatus under a 20 N load at a sliding speed of 2.7 m/sec for 20 minutes.

The Breakthrough: Key Findings & Data

The study revealed a direct and powerful correlation between applying Squeeze Casting Pressure and enhancing the alloy's mechanical properties.

Finding 1: Higher Pressure Refines Microstructure and Boosts Hardness by Over 70%

Increasing the applied pressure during solidification had a profound effect on the alloy's microstructure and hardness. The gravity-cast sample exhibited a coarser structure with large α-dendrites. In contrast, as pressure increased, the microstructure became significantly more refined. This refinement directly translated to improved hardness.

As shown in Table 3, the gravity die cast sample had a hardness of 69 VHN. This value increased steadily with pressure, reaching 82 VHN at 7.5 MPa and peaking at 118 VHN at 53 MPa—a 71% improvement over the baseline. This demonstrates that pressure is a key mechanism for achieving a finer, harder material.

Finding 2: Wear Resistance Increases Dramatically with Squeeze Casting Pressure

The enhanced hardness and refined microstructure resulted in superior wear resistance. The study measured wear rate by weight loss over a set sliding distance.

As illustrated in Figure 9, the wear rate decreased consistently as the Squeeze Casting Pressure increased. The worn surfaces, shown in Figure 10, provide visual confirmation. The gravity-cast sample (Fig. 10a) shows "continuous grooves and cracking," indicative of significant material loss. In stark contrast, the sample cast at 53 MPa (Fig. 10e) displays a "smooth and glassy finish and faint wear lines," demonstrating a mild abrasion wear mode and substantially higher durability.

Practical Implications for R&D and Operations

• For Process Engineers: This study suggests that adjusting Squeeze Casting Pressure is a direct and effective tool for controlling the final microstructure, hardness, and wear resistance of Al-Si components. The data provides a clear process window for achieving targeted mechanical properties.
• For Quality Control Teams: The data in Table 3 illustrates the effect of pressure on density and hardness. Notably, the initial drop in density at 7.5 MPa before increasing at higher pressures highlights the importance of applying sufficient pressure to not just relocate but eliminate shrinkage porosity. This could inform new quality inspection criteria.
• For Design Engineers: The findings indicate that achieving full densification and eliminating internal shrinkage defects requires sufficient applied pressure. This is a valuable consideration during the early design phase, especially for components with complex geometries where uniform pressure application is critical for structural integrity.

Paper Details

Study on the Effect of Casting Pressure on the Wear Resistance of Al-Si Alloy Prepared by Squeeze Casting

1. Overview:

• Title: Study on the Effect of Casting Pressure on the Wear Resistance of Al-Si Alloy Prepared by Squeeze Casting
• Author: Muna Khedier Abbass and Osama Sultan Muhammed
• Year of publication: 2012
• Journal/academic society of publication: JKAU: Eng. Sci., Vol. 23 No. 1
• Keywords: Squeeze casting, Wear resistance, Al-Si alloy.

2. Abstract:

In this research the effect of applied casting pressure at constant pouring and die preheating temperatures on the microstructure and wear resistance of the squeeze cast Al-Si alloy was investigated. The results showed a refinement in the microstructure with increasing of the squeeze pressure. The results also showed that the density of the specimens decreased with application of a 7.5 MPa applied pressure, but it increased steadily for higher pressures up to 53 MPa. Increasing the squeeze pressure resulted in increasing the hardness and decreasing the wear rate. These results were explained based on the densification mechanism brought about by the application of pressure during solidification.

3. Introduction:

Squeeze casting has been used for half a century in Russia and is now being exploited in the west. For example, Toyota Motor Company in Japan introduced squeeze cast aluminum alloys wheels into their product line for passenger cars in 1979[1]. The aluminum alloy 357 (Al-7Si-0.5Mg) was prepared by sand, gravity die and squeeze casting, the properties of the alloy show to be clearly superior. The improvement in ductility is particularly notable[2,3]. The commercial development of squeeze casting began to take place in Europe, North America and Japan only after 1960 as reported by Dorcic and Verma[4].

4. Summary of the study:

Background of the research topic:

Squeeze casting, also known as liquid metal forging, is a manufacturing process that combines casting with forging to produce high-quality components. It is used to produce critical aluminum components with low porosity and improved mechanical properties compared to traditional casting methods like gravity die casting.

Status of previous research:

Previous studies have shown that squeeze casting produces aluminum alloys with superior properties, such as improved ductility and fatigue resistance. Companies like Toyota have successfully used the process for commercial products like automotive wheels. Research has also explored the fatigue properties of various alloys made by squeeze casting compared to gravity and semisolid casting.

Purpose of the study:

The aim of the study was to investigate the effect of varying casting pressure (applied pressure) on the microstructure and wear resistance of a squeeze-cast Al-Si alloy, while keeping pouring and die preheating temperatures constant. The results were then compared with those from a conventional gravity die casting process.

Core study:

The core of the study involved melting an Al-12%Si alloy and casting it under five different pressure conditions: 0 MPa (gravity die casting), 7.5 MPa, 23 MPa, 38 MPa, and 53 MPa. The resulting samples were then subjected to a series of tests to measure and compare their microstructure, density, porosity, Vickers hardness, and wear rate.

5. Research Methodology

Research Design:

The research was designed as a comparative experimental study. An Al-12%Si alloy was selected and processed using two different methods: gravity die casting (as a control) and squeeze casting. Within the squeeze casting group, the applied pressure was varied as the primary independent variable to observe its effect on several dependent variables (microstructure, density, hardness, wear rate).

Data Collection and Analysis Methods:

• Microstructure: Samples were prepared via standard metallographic procedures (grinding, polishing, etching) and examined.
• Density and Porosity: Density was calculated from weight and volume measurements. Porosity was determined by comparing the actual density to the theoretical density of the alloy.
• Hardness: A Vickers hardness tester was used to measure the hardness (VHN) of the samples.
• Wear Test: A Pin-On-Disc apparatus was used to measure the wear rate based on the weight loss method after a specified sliding duration and load.

Research Topics and Scope:

The research focused on a single Al-Si alloy (AlSi12). The scope was limited to investigating the effect of applied pressure (from 7.5 to 53 MPa) at constant pouring (700°C) and die (200°C) temperatures. The study evaluated microstructure, density, porosity, hardness, and wear resistance.

6. Key Results:

Key Results:

• Increasing squeeze casting pressure leads to a refinement in the microstructure of the Al-Si alloy.
• The hardness of the alloy increases significantly with increasing pressure, from 69 VHN for the gravity-cast sample to 118 VHN for the sample cast at 53 MPa.
• The wear rate of the alloy decreases as the applied pressure increases, indicating improved wear resistance.
• The density of the samples first decreased at the lowest applied pressure (7.5 MPa) and then increased steadily with higher pressures, approaching the theoretical density at 53 MPa due to the reduction in shrinkage porosity.
• Squeeze-cast samples demonstrated superior hardness and wear resistance compared to the gravity die-cast sample.

Figure Name List:

• Fig. 1. The hydraulic press.
• Fig. 2 (a). The punch and the die on the press.
• Fig. 2 (b,c). Schematic diagrams of the squeeze punch and the die (mm).
• Fig. 3. Microstructure of gravity die cast sample A: without pressure.
• Fig. 4. Microstructure of squeeze cast sample B: at P=7.5MPa.
• Fig. 5. Microstructure of squeeze cast sample C: at P=23MPa.
• Fig. 6. Microstructure of squeeze cast sample D: at P=38MPa.
• Fig. 7. Microstructure of squeeze cast sample E: at P=53MPa.
• Fig. 8. Effect of the squeeze casting pressure on Vickers hardness number of different alloys.
• Fig. 9. Effect of the squeeze casting pressure on wear rate of alloy (Al-12%Si) at a sliding speed of 2.7 m/sec, applied load in wear test of 20 N and sliding time of 20 min.

7. Conclusion:

• The microstructure examination showed that small grain size and refine eutectic phase morphologies had been obtained in squeeze casting with respect to gravity die casting.
• The samples were produced by squeeze casting technique had higher Vickers hardness values and wear resistance than that of the gravity die technique.
• As the applied pressure for squeeze cast samples increases the hardness value increases up to 118 VHN at a squeeze pressure of (53 MPa) when compared to that of the gravity cast sample which was 69 VHN.
• The actual density of squeeze samples was improved and reached 2.67 gm/cm³ and approached the theoretical density which was 2.68 gm/cm³, because of the reduction in shrinkage porosity as applied pressure increases during solidification in squeeze casting.
• Faint wear lines in the direction of sliding on worn surfaces indicate that a mild abrasion wear mode is presented for squeeze cast samples which was produced at higher applied pressure. That means a higher wear resistance was obtained.

8. References:

• [1] Polmear, I.J., "Light Alloys, Metallurgy of the Light Metals", 2nd Edition, Edward Arnold, Great Britain (1989).
• [2] Lavington, M.H., "Mechanical Properties of 357 Aluminum Alloy produced By Different Casting Processes", Metals and Materials, 2: 713 (1986).
• [3] Chadwick, G.A., "Tensile Properties of Squeeze Cast Alloy 7010 as a Function Squeezing Pressure", Metals and Materials, 2: 693(1986).
• [4] Dorcic, J.L. and Verma, S.K., "Squeeze Casting", Metals Handbook, 9th Edition (1990).
• [5] Bonollo, F., "Squeeze Casting, An Advanced Process", Aluplanet Daily, www.aluplanet.com.
• [6] Davidson, C.J., Griffiths and J.R., Zanada, A., "Fatigue Properties of Squeeze, Semisolid and Gravity Die Cast Al-Si-Mg Alloy", SIF2004, Structural Integrity and Fracture. http://eprint.uq.edu.au./archive/0000836.
• [7] Cay, F. and Kurnaz, S.C., "Hot Tensile and Fatigue Behavior of Zinc-Aluminum Alloys Produced by Gravity and Squeeze casting", Materials and Design, 26: 479-485 (2005).
• [8] Davis, J.R., "Casting", Metals Handbook, Second Edition, part 3 (1998).
• [9] Vijian, P. and Arunachalam, V.P., "Modelling and multi objective optimization of LM24 aluminum alloy squeeze cast process parameters using genetic algorithm", J. Mat. Proc. Tech., 186: 82-86 (2007).
• [10] Renyi Casting Machinery, "Sand Casting", Sand Castings Journal, 27:Nov. (2007).
• [11] Yue, T.M., "Squeeze casting of high-strength aluminum wrought alloy AA7010", J. Mat. Proc. Tech., 66: 179-185 (1997).
• [12] The Aluminum Association, Inc., Washington, D.C., 900 19th Street, N.W. (2006) www.aluminum.org
• [13] Al-Khazraji, K.K., Moosa, A.A. and Muhammed, O.S., "Microstructure, Density, Hardness and Wear Resistance of Squeeze Cast Graphite Particles Reinforced Aluminum-Silicon Composites", Proceeding of the first scientific conference on nanotechnology,
• [14] ASTM, "Metals Test Method and Analytical Procedure", Vol. 05.02 (1989).
• [15] U. N. I. D. O., "Advances in Material Tech.", Monitor Vienna International Center, Austria, pp: 9-11 (1990).
• [16] Maleki, A., Niroumand, B. and Shafyei, A., "Effects of squeeze casting parameters on density, macrostructure and hardness of LM13 alloy", Mat. Sci. Eng., A428: 135-140 (2006).
• [17] Raji A. and Khan R.H., "Effects of pouring temperature and squeeze pressure on Al-8 % Si alloy squeeze cast parts", AU J. T., 9(4): 229-237 (2006).
• [18] Sukumaran, K., Ravikumar, K.K., Pillai, S.G.K., Rajan, T.P.D., Ravi, M., Pillai, R.M. and Pai, B.C., "Studies on squeeze casting of Al 2124 alloy and 2124 -10% SiCp metal matrix composite", Materials Science and Engineering A, 490: 235-241(2008).
• [19] Franklin, J.R. and Das, A.A., "Squeeze Casting – A Review of the Status", British Foundryman Journal, 77: 150-158 (1984).

Expert Q&A: Your Top Questions Answered

Q1: Why was an Al-12%Si alloy specifically chosen for this study?

A1: The Al-12%Si alloy was selected because its eutectic composition provides very good castability and excellent weldability. According to the paper, this alloy also has a low melting point (570°C) and is particularly suitable for intricate, thin-walled, and leak-proof castings, making it a relevant material for industrial applications where these properties are valued.

Q2: The paper notes in Table 3 that density decreased at the lowest applied pressure (7.5 MPa) before increasing at higher pressures. Why did this occur?

A2: This counterintuitive result is explained by the densification mechanism. In gravity casting, shrinkage often forms a large pipe or cavity on the top surface. When a low pressure like 7.5 MPa is applied, it's sufficient to push this shrinkage pipe and other cavities down into the bulk of the casting but not strong enough to completely eliminate them. This redistribution of porosity results in a lower overall density. At higher pressures (23 to 53 MPa), the force is great enough to reduce and eliminate these gas and shrinkage porosities, leading to a steady increase in density.

Q3: What specific changes in the microstructure were observed as the Squeeze Casting Pressure increased?

A3: The primary change was a significant refinement of the microstructure. As shown in Figures 3 through 7, the gravity-cast sample (Fig. 3) had a coarse structure with large α-dendrites. In comparison, the squeeze-cast samples showed a finer eutectic phase and smaller grain size. This refinement became more pronounced as the pressure was increased from 7.5 MPa up to 53 MPa.

Q4: How was the wear rate measured, and what were the specific test conditions?

A4: The wear rate was determined using the weight method with a Pin-On-Disc wear apparatus, designed according to ASTM specification F732-82. The key test conditions, as stated in the paper, were a constant applied load of 20 N, a sliding time of 20 minutes, and a sliding speed of 2.7 m/sec. The initial surface roughness of the wear specimens was Ra= 0.20µm.

Q5: The conclusion mentions a "mild abrasion wear mode" for high-pressure samples. What visual evidence from the study supports this claim?

A5: This conclusion is supported by the micrographs of the worn surfaces presented in Figure 10. The gravity die cast sample (Fig. 10a) shows "continuous grooves and cracking of long wear track." In contrast, the sample squeeze-cast at 53 MPa (Fig. 10e) exhibits a "smooth and glassy finish and faint wear lines in the direction of sliding." This visual difference indicates a shift from a severe wear mechanism to a much milder form of abrasion, confirming higher wear resistance.

Conclusion: Paving the Way for Higher Quality and Productivity

This research provides clear, quantitative evidence that Squeeze Casting Pressure is a critical parameter for enhancing the performance of Al-Si alloys. By increasing pressure during solidification, manufacturers can directly influence microstructure refinement, reduce porosity, and achieve significant gains in hardness and wear resistance. This data-driven approach moves beyond trial-and-error, offering a reliable pathway to produce components that are stronger, more durable, and better suited for demanding applications.

At CASTMAN, we are committed to applying the latest industry research to help our customers achieve higher productivity and quality. If the challenges discussed in this paper align with your operational goals, contact our engineering team to explore how these principles can be implemented in your components.

Copyright Information

• This content is a summary and analysis based on the paper "Study on the Effect of Casting Pressure on the Wear Resistance of Al-Si Alloy Prepared by Squeeze Casting" by "Muna Khedier Abbass and Osama Sultan Muhammed".
• Source: https://doi.org/10.4197/Eng.23-1.1

This material is for informational purposes only. Unauthorized commercial use is prohibited.
Copyright © 2025 CASTMAN. All rights reserved.