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Changan Automobile and Baowu Magnesium have successfully completed trial production of a magnesium alloy rear underbody Gigacasting in Chongqing. The component met all targets for dimensional accuracy, mechanical performance, and surface quality.
Engineers created a completely new structural design and used simulation optimization. Compared with conventional aluminum rear underbody structures, the magnesium version delivers more than 20% weight reduction while improving overall body structural integrity and crash safety performance.
The partners also developed a new high-performance magnesium alloy. Through advanced composition design, multi-element micro-alloying, and refined grain control, yield strength, tensile strength, and elongation each are reported to be improved by more than 25% versus conventional commercial magnesium alloys.
The team had to solve challenges in high-tonnage clean magnesium melting, complex thin-wall filling, precise mold temperature control, and closed-loop defect management. The first trial achieved a 67% yield rate.
Changan plans to accelerate process optimization toward mass production to support lightweighting of new energy vehicles. Currently, as seen in the past, such projects never entered mass production and are all still in their development stage.
Gigacasting plants using magnesium alloys, vehicle programs with magnesium Gigacasting technoloy and Giga-Thixomolding machines are all tracked in The Gigacasting Database.
Why only ~20% weight reduction — not ~33–36%?
Magnesium’s density is ~1.74 g/cm³ vs ~2.70 g/cm³ for aluminum — roughly 64% of aluminum’s density.
For identical geometry and volume, that implies a theoretical weight saving of ~36%. Many Mg alloys also offer competitive specific strength. Yet real-world structural castings usually deliver often 22–28% with good design.
The key reason is stiffness, not density or strength alone.
Gigacastings are stiffness-driven. Absolute stiffness is the resistance to bending, torsion and deflection under load.
Young’s modulus (E) = material stiffness (how much it resists elastic deformation).
Mg ≈ 45 GPa | Al ≈ 70 GPa
For plates, shells or thin-walled castings in bending, stiffness scales with:
E × t³ (where t = wall/section thickness)
To deliver the same bending stiffness when switching from Al to Mg, thickness must increase by the cube root of the modulus ratio:
t_Mg / t_Al = (E_Al / E_Mg)^{1/3} = (70 / 45)^{1/3} ≈ 1.16
→ ~16% thicker walls needed = only ~25% weight saving.
The gap to the full density-based theoretical saving of 33% comes from the need for modestly thicker sections or adjusted geometry to compensate for the lower absolute modulus.
