Lightweighting of a hybrid transmission housing by replacing ADC12 with AZ91D magnesium alloy

This case report investigates the engineering replacement of an established ADC12 hybrid transmission housing with AZ91D magnesium alloy. The validated ADC12 design was used as the baseline, and the directly substituted AZ91D housing was evaluated through CAE in terms of structural strength, external-load deformation and sealing, modal behavior, dynamic stiffness, and equivalent radiated power. The identified performance weaknesses were addressed through targeted structural revisions and subsequent reassessment. The revised front, middle, and rear housings were then manufactured by high-pressure die casting and machining, with process adaptations and quality-control procedures developed for AZ91D. The total housing mass was reduced from 28.9 kg to 23.1 kg, corresponding to a 20% weight reduction. Reassessment showed that the structural revisions effectively recovered the key structural, sealing, and NVH-related performance of the magnesium-alloy housing, while prototype production and inspection confirmed its manufacturing feasibility. This case demonstrates that successful replacement of ADC12 by AZ91D requires an integrated engineering route combining material substitution, performance verification, structural revision, manufacturing adaptation, and prototype validation.