Abstract
The aluminum alloy A2024-T3 was overaged at 573 K for different aging times, and then subjected to the hardness measurement and the fatigue testing. The hardness decreased successively with increasing aging time, but the fatigue life largely decreased to a half of the initial life after aging for 2 h or longer. The ultrasonic measurement was carried out with overaged specimens to examine changes in ultrasonic parameters with the aging time. The peak intensity (PI) gradually decreased with increasing aging time, but the average gradient of the transfer function (AGTF) largely decreased and became almost constant after aging for 2 h or longer. The ultrasonic measurement was also carried out in-process during the fatigue testing by using the water bag. The ultrasonic parameters (PI and AGTF) increased with the number of fatigue cycles (N) with considerable scatter, and the average rate of AGTF in the fatigue process (d(AGTF)/dN) increased with the aging time up to 4 h.
