Aging process during creep deformation in an Al-Mg-Si alloy affected by pre-aging condition

Creep behavior of an Al-0.3%Mg-0.5% Si alloy affected by pre-aging condition was investigated to obtain fundamental knowledge on the thermal stability in the service temperature range for the precipitation-hardened aluminum heat-exchanger. The alloy was aged at 175 degrees C for 3 h (under-aged) and 24 h (peak-aged), after solution treatment, and then subjected to creep testing at temperatures of 150 degrees C and 200 degrees C. When the creep temperature was 150 degrees C, the under-aged (UA) specimen showed a lower creep rate than that of the peak-aged (PA) specimen. On the other hand, when the creep temperature was 200 degrees C, both specimens showed almost the same creep rate. In other words, the UA specimen had higher creep resistance than the PA specimen at 150 degrees C, whereas this advantage disappeared at 200 degrees C. The difference was thought to originate from the precipitation during creep testing.