Abstract:The effects of pre-stretching following solution treatment on the hardness and microstructures of aged 2524 aluminium alloy at 170 °C were studied. Ageing hardness values under different pre-stretching conditions were measured, and the corresponding microstructures were characterized by transmission electron microscopy (TEM). The results show that compared with unstretched samples, the peak hardness is increased and the time to reach the peak hardness is reduced with the increase of pre-strain; the number density of S (Al₂CuMg) phases is increased and the length is shortened in pre-stretched alloy. Additionally, the number density of GPB zones is decreased with the increase of pre-strain in peak-aged samples. When the pre-strain is up to 5%, S phases play the predominant contribution to the peak hardness. Fine and uniformly distributed S phases lead to a higher hardness than GPB zones together with S phases existing in conventionally aged 2524 alloy.

Key words: 2524 aluminium alloy; pre-stretch; S phase; GPB zone