Comparative Failure Analysis of A356 and ADC12 Aluminium Alloy Clutch Brackets for Automotive Transmission Applications
Keywords:
aluminium alloy; clutch system; failure analysis; hardness; clutch bracketAbstract
The bracket and clutch cable serve as a mechanical link between the clutch pedal inside the cabin and the release fork in the transmission. Failure of this component can disrupt gear-shifting performance and reduce vehicle reliability. Although aluminium alloy brackets are widely used in automotive applications for their lightweight properties, information on the failure behaviour of transmission brackets in city cars remains limited. Therefore, this study aimed to investigate the mechanical properties, microstructural characteristics, and fracture behaviour of aluminium alloy transmission brackets from two different aluminium alloys. The research used metallographic examination, and fractographic analysis with Scanning Electron Microscopy (SEM) and hardness testing. Specimens were sectioned transversely from the bracket component, prepared using standard metallographic procedures, and examined to identify microstructural features and fracture mechanisms. The results showed that both brackets exhibited a relatively homogeneous Al–Si alloy microstructure with rounded grains and spherical porosity, indicating that they were manufactured by high-pressure die casting. The ADC12 aluminium alloys had a higher average hardness of 91.5 HV than A356, which had 78.8 HV. Fractographic observations revealed that the A356 bracket was dominated by ductile fracture characterized by microvoid coalescence, whereas the ADC12 bracket exhibited mixed brittle–ductile fracture features associated with silicon-rich and intermetallic phases. In both samples, casting porosity acted as a stress concentrator and potential crack initiation site. These findings indicate that variations in casting quality and microstructural characteristics significantly influence the hardness and fracture behaviour of aluminium alloy transmission brackets. The study provides useful insights for improving material selection, casting quality control, and the reliability of automotive transmission linkage components.
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