A.A. Khan, Al-K. Hossain, M.S. Kaiser

Role of Si at a lower level on the mechanical properties of Al-based automotive alloy

J. Min. Metall. Sect. B-Metall., 59 (1) (2023) 147-154. DOI:10.2298/JMMB230131013K
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Available online 30 May 2023
(Received 31 January 2023; Accepted 16 May 2023)


The effect of silicon, at a lower level around 3.5 wt% on the tensile, notched impact, and fracture properties of Al-based alloys for the automotive industry was investigated by T6 heat treatment. The results show that the tensile strength in the aged alloys increases mainly due to the development of Al2Cu and Mg2Si precipitates within the Al-matrix. The alloy with higher Si content exhibits higher strength due to the formation of Si-rich precipitates which impede the dislocation movement and cause higher values of true strain with a change in tensile behaviour. The ductility of the alloys decreases with the treatment temperature in favour of GP zones, βʹʹ, βʹ, β-precipitates formation and the formation of \ Qʹʹ phase and finally increases after the coarsening of the precipitates. Microstructural examination confirms the coarse grain boundary and the plate-like eutectic phase when Si is added. Fractography shows a small dimple structure originating from the Al dendrites and the crack is initiated through brittle Si-rich particles.

Keywords: Automotive Al-alloy; T6 heat treatment; True stress-strain; Impact strength; Fractography

Correspondence Address:
M.S. Kaiser,
Directorate of Advisory, Extension and Research Services, Bangladesh University of Engineering and Technology, Bangladesh;
email: mskaiser@iat.buet.ac.bd

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