The Effect of Artificial Aging on Tensile Work Hardening Characteristics of a Cast Al-7 Pct Si-0.55 Pct Mg (A357) Alloy

Al-7 pct Si-0.55 pct Mg (A357) alloy specimens excised from continuously cast bars were solution treated at 540 °C for 22 hours, quenched, and finally aged artificially at 155 °C, 175 °C, and 205 °C for various times. Tensile work hardening characteristics were investigated using Kocks–Mecking (KM) plots for every specimen out of the 90 totally investigated. Each specimen followed the stage III KM work hardening model. The effect of artificial aging, i.e., matrix strength on the KM work hardening model parameters, was investigated. The results of the current analysis indicated that (1) unlike previously found for wrought Al-Mg-Si alloys, the shearing-bypassing transition in β″ precipitates takes place at peak strength, (2) the transition from stage II to III work hardening is affected by yield strength and temper, (3) the KM parameters are strongly affected by artificial aging, and (4) the elongation to fracture is determined by stage III work hardening, especially by parameter K of the KM model.