Research progress on squeeze casting in China

Beyond HPDC: Unlocking Superior Mechanical Properties with Squeeze Casting Technology

This technical summary is based on the academic paper "Research progress on squeeze casting in China" by Li Yuanyuan, Zhang Weiwen, Zhao Haidong, You Dongdong, Zhang Datong, Shao Ming, and Zhang Wen, published in CHINA FOUNDRY (2014).

Keywords

• Primary Keyword: Squeeze Casting Technology
• Secondary Keywords: High Performance Aluminum Alloys, Metal Matrix Composites, Liquid Forging, Near-Net-Shape Forming, Casting Process Optimization

Executive Summary

• The Challenge: The rising demand for lightweight, high-performance metal parts requires a casting process that overcomes the limitations of traditional methods, offering both the precision of casting and the properties of forging.
• The Method: The paper reviews the progress of squeeze casting (also known as liquid forging) in China, a process where liquid metal solidifies under high pressure to produce dense, high-integrity components.
• The Key Breakthrough: Chinese researchers have developed high-performance aluminum alloys, like the Al-Cu-Mn based HGZL03, which achieve a tensile strength of 440 MPa and 20% elongation, and have proven that squeeze casting can significantly increase the tolerance for iron impurities in aluminum alloys.
• The Bottom Line: Squeeze casting technology is a mature and powerful process for manufacturing complex, high-performance components, enabling the use of advanced alloys and even recycled materials without compromising mechanical properties.

The Challenge: Why This Research Matters for HPDC Professionals

In the automotive, aerospace, and defense industries, the push for lightweighting and enhanced performance is relentless. While traditional casting methods are effective, they can face limitations in achieving the ultra-high mechanical properties and microstructural uniformity required for the most demanding structural parts. Engineers are constantly seeking manufacturing routes that are short, efficient, and precise, combining the best features of casting (complex shapes) and plastic processing (excellent properties). This research was driven by the urgent need to advance a technology that could meet these demands, particularly for large, complex, and high-performance lightweight components, which have become a major focus in Chinese manufacturing over the past two decades.

The Approach: Unpacking the Methodology

The paper provides a comprehensive review of research progress in China, focusing on three key areas:

1. Materials Development: Researchers systematically studied various alloys for squeeze casting, including aluminum, magnesium, zinc, and copper. A significant focus was placed on developing new high-performance aluminum alloys (e.g., the HGZL series) and investigating the effect of the squeeze casting process on common impurities like iron. The studies involved preparing alloys via squeeze casting under varying pressures (up to 120 MPa) and conducting mechanical property tests (tensile strength, elongation) and microstructural analysis.
2. Process Optimization & Simulation: The research explored the optimization of key process parameters like pressure, temperature, and dwelling time. Advanced numerical simulation, including finite element modeling, was employed to analyze the filling and solidification behavior. For instance, simulations were used to optimize a multi-stage injection process for casting a large aluminum wheel, considering turbulence, heat transfer, and die friction to prevent defects.
3. Equipment Development: The paper highlights the significant progress in designing and manufacturing specialized squeeze casting equipment in China. This includes the development of large-tonnage machines with clamping forces up to 40,000 kN, as well as novel process equipment for techniques like electromagnetic force filling and closed-mold pouring.

The Breakthrough: Key Findings & Data

[Based on the paper's Results section, present the 2-3 most significant findings with concrete data.]

Finding 1: Development of High-Performance Al-Cu-Mn Alloy (HGZL03)

A major breakthrough was the development of the HGZL03 alloy, an Al-Cu-Mn based material. Under an applied pressure of 75 MPa, this alloy demonstrates a remarkable combination of strength and ductility. As shown in Figure 1, the tensile strength in the T5 heat-treated state reaches 440 MPa, with an elongation of 20%. This performance level is close to that of forged components, showcasing the potential of squeeze casting to produce high-integrity structural parts.

Finding 2: Increased Tolerance for Iron Impurities in Aluminum Alloys

Iron is typically a harmful impurity in high-performance aluminum alloys, but the study found that squeeze casting significantly mitigates its negative effects. For an Al-5.0Cu-5.0Mn alloy with 0.5wt.% Fe, squeeze casting under 75 MPa resulted in a tensile strength of 395 MPa and 14% elongation. Compared with gravity die casting, these values represent increases of 30% and 140%, respectively. The process transforms the harmful, needle-like β-Fe phase into a less detrimental Chinese-script α-Fe phase (Figure 2) and reduces casting defects, relaxing the strict iron content limits and enabling the use of recycled aluminum scrap.

Practical Implications for R&D and Operations

• For Process Engineers: This study suggests that adjusting applied pressure is a powerful tool for refining microstructure and improving mechanical properties. The data in Figure 1 shows that for the HGZL03 alloy, properties improve significantly up to 75 MPa, indicating a target pressure range for process optimization.
• For Quality Control Teams: The data in Figure 2 of the paper illustrates the effect of high pressure on transforming detrimental iron-rich phases. This could inform new microstructural inspection criteria for parts made from secondary or recycled aluminum, allowing for higher iron content without sacrificing performance.
• For Design Engineers: The findings indicate that squeeze casting enables the production of large, complex parts like the 670 mm diameter wheel and the transmission supporting frame (Figure 5) with excellent mechanical properties (350-390 MPa tensile strength). This opens up possibilities for designing large, lightweight, single-piece components that were previously impossible to cast with such high performance.

Paper Details

Research progress on squeeze casting in China

1. Overview:

• Title: Research progress on squeeze casting in China
• Author: Li Yuanyuan, Zhang Weiwen, Zhao Haidong, You Dongdong, Zhang Datong, Shao Ming, and Zhang Wen
• Year of publication: 2014
• Journal/academic society of publication: CHINA FOUNDRY, Vol.11 No.4 July 2014
• Keywords: squeeze casting; research progress; technology; equipment

2. Abstract:

Squeeze casting is a technology with short route, high efficiency and precise forming, possessing features of casting and plastic processing. It is widely used to produce high performance metallic structural parts. As energy conservation and environmental protection concerns have risen, lightweight and high performance metal parts are urgently needed, which accelerated the development of squeeze casting technology over the past two decades in China. In this paper, research progress on squeeze casting alloys, typical parts manufacturing and development of squeeze casting equipment in China are introduced. The future trend and development priorities of squeeze casting are discussed.

3. Introduction:

Squeeze casting, also known as liquid forging, is a special casting technique whereby a certain amount of liquid metal is injected into the mold cavity at low speed, then solidified to form castings under pressure. Compared with other casting methods, squeeze casting has a wide range of materials selection, high utilization rate of liquid metal, uniform and dense casting microstructures, excellent mechanical properties, high surface finish and dimensional accuracy. Compared with plastic deformation methods, squeeze casting can make complex parts with lower deformation force and fewer working procedures. In short, squeeze casting is a technology with a short route, high efficiency and precise forming, and possesses the features of both casting and plastic processing. It is widely used in machinery, automobile, household, aerospace and defense industries to produce high performance and high precision parts.

4. Summary of the study:

Background of the research topic:

The urgent need for lightweight and high-performance products, driven by energy conservation and environmental protection concerns, has led to a renewed and widespread focus on squeeze casting technology in China since the early 1990s. This technology combines the advantages of casting and forging, making it ideal for producing high-integrity structural parts.

Status of previous research:

The concept of squeeze casting dates back to 1819, but its formal establishment is credited to a 1960s monograph by Soviet scientist V. M. Plyatskii. The technology saw rapid development in Europe and North America in the 1960s. China began research in the 1960s with a rapid development phase in the 1970s. However, the last two decades have seen accelerated progress due to industrial demand.

Purpose of the study:

This paper aims to review the research progress on squeeze casting in China over the past two decades. It introduces advancements in squeeze casting alloys, the manufacturing of typical parts, and the development of specialized squeeze casting equipment. It also discusses future trends and development priorities for the technology.

Core study:

The core of the study is a review of Chinese research and development in three main areas:
1. Squeeze Casting Materials: Focuses on aluminum and magnesium alloys, as well as metal matrix composites. It details the development of new high-performance alloys and methods to improve tolerance to impurities.
2. Squeeze Casting Process and Typical Parts: Discusses process optimization, numerical simulation of filling and solidification, and showcases examples of large, complex parts like automotive wheels and transmission frames.
3. Squeeze Casting Equipment: Outlines the progress in developing serialized and large-size squeeze casting machines in China, moving from retrofitted hydraulic presses to specialized, high-tonnage equipment.

5. Research Methodology

Research Design:

The study is a comprehensive literature review, synthesizing research findings from various universities, institutes, and companies across China. It aggregates data from experimental studies, numerical simulations, and industrial applications.

Data Collection and Analysis Methods:

The authors collected and analyzed data from numerous technical papers, patents, and industrial reports. The analysis focuses on mechanical property data (tensile strength, elongation), microstructural characterization (SEM images), results from numerical simulations (temperature and pressure fields), and specifications of developed equipment.

Research Topics and Scope:

The scope is limited to research progress within China. The main topics covered are:
- Development of aluminum, magnesium, zinc, and copper alloys for squeeze casting.
- Preparation and properties of metal matrix composites via squeeze casting.
- Numerical simulation and optimization of the squeeze casting process.
- Manufacturing of large, complex components for automotive and other industries.
- Development of advanced, high-tonnage squeeze casting machinery.

6. Key Results:

Key Results:

• Development of a series of high-performance squeeze casting aluminum alloys, including HGZL03 (Al-Cu-Mn based), which achieves 440 MPa tensile strength and 20% elongation under 75 MPa pressure.
• Demonstration that the squeeze casting process can increase the maximum allowable iron content in aluminum alloys by transforming harmful needle-like β-Fe phases into less detrimental α-Fe phases, improving mechanical properties by up to 30% (strength) and 140% (elongation) compared to gravity casting.
• Successful manufacturing of large, complex parts, such as a 670 mm diameter wheel and a 580 mm × 480 mm transmission support frame, with excellent mechanical properties and no gas or shrinkage defects.
• Advancement in numerical simulation, enabling the optimization of multi-stage injection processes to reduce turbulence and ensure complete filling in complex molds like an automotive wheel.
• Significant progress in domestic equipment manufacturing, including the development of a 40,000 kN clamping force squeeze casting machine, one of the world's largest.

Figure Name List:

• Fig. 1: Tensile strength (a) and elongation (b) of HGZL03 alloy under different applied pressures
• Fig. 2: Microstructures of Al-5.0Cu-0.6Mn-0.5Fe alloy under pressures of 0 MPa (a) and 75 MPa (b)
• Fig. 3: Microstructures of hybrid enhanced C/LF6 aluminum matrix composites prepared by squeeze casting: C/LF6 aluminum matrix composites (a); C+SiC/LF6 aluminum matrix composites (b)
• Fig. 4: Simulation of filling behavior for in-direction squeeze casting wheel by multi-stage injection
• Fig. 5: Squeeze casting wheel (a) and transmission supporting frame (b)
• Fig. 6: Electromagnetic force indirect filling squeeze casting

7. Conclusion:

Significant progress in squeeze casting has been made in China over the past two decades, driven by the demand for lightweight, high-performance metal parts. The main focus has been on Al- and Mg-based alloys and their composites. Research on the process itself includes optimization, numerical simulation, and the manufacturing of large, complex light-weighted parts. In equipment research, the focus is on developing serialized, advanced equipment with high efficiency and precision. Squeeze casting technology has great potential to improve alloy performance, promote the use of aluminum over steel, reduce component weight, and realize efficient near-net-shape forming, contributing to energy saving and sustainable development.

8. References:

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Expert Q&A: Your Top Questions Answered

Q1: What makes squeeze casting particularly suitable for producing metal matrix composites (MMCs)?

A1: The paper highlights three key advantages. First, the high pressure improves the fluidity of the molten metal, ensuring it completely fills the gaps between the reinforcement materials (like fibers or particles) to create a void-free structure. Second, the process is rapid, which shortens the contact time between the hot metal and the reinforcement, slowing down undesirable interfacial reactions. Finally, the technology is versatile, allowing for a wide range of matrix materials (Al, Mg, Zn, Cu) and reinforcements (fibers, whiskers, particles).

Q2: How exactly does squeeze casting pressure mitigate the negative effects of iron in aluminum alloys?

A2: The research shows that the high pressure and enhanced cooling rate during solidification fundamentally alter the iron-rich phases. As seen in Figure 2, in a gravity-cast alloy, iron forms a harmful, needle-like β-Fe (Al₇Cu₂Fe) phase that acts as a stress concentrator. Under 75 MPa of pressure, this phase completely transforms into a more compact, less detrimental "Chinese-script" α-Fe (Al₁₅(Mn,Fe)₃Si₂) phase. This morphological change, combined with an overall reduction in the size and number of these phases, leads to a dramatic improvement in ductility and strength.

Q3: The paper mentions the high-performance HGZL03 alloy. What is its composition and why does it perform so well under pressure?

A3: HGZL03 is an Al-Cu-Mn based alloy with a composition of 4.5-5.5% Cu, 0.2-0.8% Mn, and trace elements of Zr, V, Ti, B, and rare earth. Its excellent performance stems from the effect of the squeeze casting process. The high pressure refines the grain structure, reduces micro-porosity, and ensures a uniform and dense microstructure. This eliminates common casting defects and allows the alloy to achieve its full potential, resulting in the high strength (440 MPa) and ductility (20%) shown in Figure 1.

Q4: For the large wheel casting, why was an optimized multi-stage injection process necessary?

A4: A single, constant injection speed for a large, complex part like a wheel can cause problems like gas and oxide entrapment. The simulation results in Figure 4 show that the optimized multi-stage injection addresses this. In the first stage, a high injection velocity reduces contact time with the die, minimizing heat loss. In the second stage, the velocity is reduced as the melt flows into complex areas, preventing turbulence. In the final stage, the melt moves upwards steadily to complete the filling. This controlled process reduces filling time, minimizes solidification during filling, and ensures a defect-free casting.

Q5: The paper proposes an indirect squeeze casting method using electromagnetic force filling. What is the main advantage of this approach?

A5: The primary advantage of the electromagnetic force filling method, shown in Figure 6, is improved melt quality. In this setup, the molten metal is transferred from the holding furnace through a pipeline into the die cavity within a hermetic (sealed) space. This prevents the melt from being exposed to the atmosphere, minimizing oxidation and gas pickup. By guaranteeing a cleaner melt before the application of pressure, the final casting has higher integrity and better properties.

Conclusion: Paving the Way for Higher Quality and Productivity

This review of Chinese research highlights the significant advancements in Squeeze Casting Technology, confirming its role as a critical manufacturing process for producing next-generation lightweight components. The ability to create complex, near-net-shape parts with forged-like mechanical properties and even utilize recycled materials without performance degradation presents a powerful value proposition. For industries where strength, weight, and reliability are paramount, these findings offer a clear path toward higher quality and productivity.

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 "Research progress on squeeze casting in China" by "Li Yuanyuan, et al.".
• Source: CHINA FOUNDRY, Vol.11 No.4 July 2014, pp. 239-246.

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