Paint-bake response of AZ80 and AZ31 Mg alloys

Aging behaviors of extruded and rolled AZ80 and AZ31 Mg alloys were investigated under conditions similar to the paint-bake cycle currently used in automotive industry. Artificial aging at 170 degrees C from 0.5 to 12 h was conducted on solution-treated specimens to study the effects of aging on mechanical properties. SEM observations and EDS data show that beta-phase of Al12Mg17 precipitates continuously or discontinuously from alpha-Mg matrix and distributes along grain boundaries of the AZ80 alloy during artificial aging. Data of tensile tests and Vickers hardness tests show that an optimum mechanical property is achieved after baking at 170 degrees C for 6-8 h when Vickers hardness, tensile strength, and elongation are increased by 6.35%, 15.30%, and 7.88%, respectively, while the AZ31 alloy does not exhibit significant hardening behavior over the aging period.