Time and Strain Response of Repeated Ageing Treatments on Recycled Al-Si-Cu Alloy

The objective of this study was to investigate the time response of 3-stage artificial ageing treatments on strength properties of recycled Al-Si-Cu alloy with a view to obtaining useful empirical relationships for predicting required treatment cycles. True compressive stress, micro hardness and strain (%) were evaluated in response to ageing time and repeated ageing. The results of compression and hardness tests showed that alloy hardness and compressive stress increased with ageing time, and that these properties also increased with repeated ageing. The results also showed that alloy strain (%) reduced with ageing time and repeated ageing, indicating increasing strength or strain hardening of the alloy with repeated ageing. Using these results, empirical models of the form n = 0eαt, and n = 0eαN are established for predicting the required ageing time and/or number of ageing treatments to raise the strength (or hardness) of an alloy to desired levels to meet service requirements. The strain response of the alloy is modelled as εn = ε0e αt.