Key Takeaways & Executive Findings
- •• The spatial distribution of microstructure and mechanical properties in HPDC AE81 magnesium alloy battery module ends is governed by filling behavior and solidification sequence, with externally solidified crystals (ESCs) decreasing along the flow path toward the overflow gate, leading to finer grains and slightly higher yield strength. • Porosity is the dominant factor controlling ductility and tensile strength; the gate region exhibits the highest porosity (0.74%) and lowest elongation (4.3%) and ultimate tensile strength (218 MPa), while other regions with lower porosity (0.33%-0.39%) achieve elongation of 6%-7% and UTS of 235-242 MPa. • Yield strength follows the Hall-Petch relationship, whereas elongation and tensile strength are negatively correlated with pore volume fraction, providing a quantitative microstructure-property relationship for HPDC magnesium alloys. • The findings elucidate the mechanism behind performance gradients in HPDC magnesium alloys and offer a theoretical basis for designing lightweight components for new energy vehicles, supporting the application of AE81 alloy in critical load-bearing structures.
Abstract
AE81 magnesium alloy castings for electric vehicle battery module ends were fabricated using high pressure die casting (HPDC). Effects of filling behavior and solidification sequence on the spatial distribution of microstructure and mechanical properties were systematically investigated. The results indicate that along the flow path toward the overflow gate, the area fraction of externally solidified crystals (ESCs) gradually decreases, and the average grain size becomes finer, resulting in a slight increase in yield strength. In addition, the pores’ volume fraction significantly affects ductility and tensile strength, with the gate region exhibiting the highest porosity (0.74%) and thus the lowest elongation (4.3%) and ultimate tensile strength (218 MPa). In other regions, the porosity decreases to 0.33%-0.39%, resulting in increased elongation (6%-7%) and higher ultimate tensile strength (235-242 MPa). Analysis of the microstructure-property relationship reveals that the yield strength follows the Hall-Petch relationship, while elongation and tensile strength are negatively correlated with pore volume fraction. This finding elucidates the mechanism behind the formation of performance gradients in HPDC magnesium alloys and provides a theoretical basis for the design of lightweight components in new energy vehicles.
1. Introduction
In response to the twin global challenges of environmental deterioration and energy scarcity, promoting new energy vehicles has become a viable strategy for lowering CO2 emissions and reducing reliance on fossil fuels [1-4]. Within this context, vehicle lightweighting technology has attracted considerable attention as a key direction for the development of electric vehicles. Magnesium alloys, owing to their low density (only two-thirds that of aluminum and one-quarter that of steel) [5, 6], high specific strength [7], and excellent damping capacity [8], are widely recognized as the most promising lightweight metallic materials. These characteristics endow magnesium alloys with significant engineering value in weight reduction for new energy vehicles [9, 10], especially in the lightweight design of key components such as battery pack structures and vehicle body frames.
High pressure die casting (HPDC) is a key manufacturing technique for magnesium alloy automotive parts, offering an exceptional surface finish and capacity to produce thin-walled, complex geometries [11, 12]. Compared with aluminum alloys, HPDC of magnesium alloys significantly extends die life and improves production efficiency. It has been widely applied in mass production of small to medium-sized structural components such as steering wheels, shock towers, and dashboard brackets, achieving notable energy-saving and emission-reduction benefits [3]. However, commercially available die-cast magnesium alloys are still mainly limited to low-strength AM series (AM50A, AM60B) [13, 14] and AZ series (AZ91D) [15], whose room-temperature mechanical properties are generally low, making them inadequate for structural applications in electric vehicles. To overcome this technical bottleneck, our research team has developed a novel HPDC AE81 magnesium alloy (Mg-8Al-0.7Zn-1.5Ce-0.25Mn-0.25Sb-0.1Sr) through a multi-element microalloying design approach [16]. While maintaining cost competitiveness, this alloy exhibits an excellent combination of mechanical properties, with a room-temperature yield strength (YS) of 190±6.1 MPa, an ultimate tensile strength (UTS) of up to 290±9.8 MPa, and an elongation (EL) of approximately 10%, achieving an optimal balance of strength, ductility, and economy. It offers an ideal lightweight material solution for critical load-bearing components in electric vehicles.
During the HPDC process of automotive thin-walled structural components, the metal melt undergoes complex physical phenomena including slow movement in the shot sleeve, high-speed and high-pressure mold filling, and non-equilibrium solidification [17, 18]. Th
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He-cong Xie, Jiang-feng Song, Chuang-ming Li, Zhi-hua Dong, Ang Zhang, Jiang Zheng, Dao-yan Yang, Wei Ren, Xian-yue Qin, Hong-fen Feng, Dong-xia Xiang, Bin Jiang (2026). Microstructure and mechanical properties of high pressure die casting AE81 magnesium alloy battery module ends. China Foundry. https://doi.org/10.1007/s41230-026-5154-x
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Frequently Asked Questions
What is the AE81 magnesium alloy and why is it used for battery module ends?
AE81 is a novel high-pressure die-casting magnesium alloy developed for electric vehicle applications. It offers a balance of strength, ductility, and cost-effectiveness, making it suitable for lightweight structural components like battery module ends.
How does porosity affect the mechanical properties of HPDC AE81 alloy?
Porosity significantly reduces ductility and tensile strength. In the study, the gate region with highest porosity (0.74%) showed lowest elongation (4.3%) and UTS (218 MPa), while regions with lower porosity (0.33%-0.39%) achieved higher elongation (6%-7%) and UTS (235-242 MPa).
What is the relationship between grain size and yield strength in this alloy?
Yield strength follows the Hall-Petch relationship, meaning finer grains lead to higher yield strength. The study found that along the flow path, grain size decreased, resulting in a slight increase in yield strength.
What are the key findings of this research?
The research reveals that filling behavior and solidification sequence cause spatial variations in microstructure and mechanical properties. It identifies porosity as the dominant factor for ductility and tensile strength, and provides a theoretical basis for designing lightweight components.
How does this research contribute to electric vehicle lightweighting?
By understanding the microstructure-property relationships in HPDC AE81 alloy, manufacturers can optimize casting processes to reduce defects and improve mechanical performance, enabling the production of lighter and stronger components for electric vehicles.
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