Cyclic hardening/softening behaviour in AZ31B magnesium alloy based on infrared thermography

Abstract

The work-hardening/softening behaviour of AZ31B magnesium alloy during high cycle fatigue was investigated. The superficial temperature evolution during fatigue tests was used as a criterion for the different levels of work-hardening/softening. The microstructures under different cycles were observed by transmission electron microscope. Tensile test (with post-fatigue) was conducted to quantify the work-hardening/softening behaviour which showed that high dislocation density after cyclic loading lead to high tensile strength. The temperature evolution of the specimens with different levels of work-hardening/softening during tensile tests is related to the microstructures; the results indicated that the temperature rise of the specimen with high density dislocation was lower. Microstructures after tensile tests showed that high dislocation density after cyclic loading would lead to high twinning density.

Rapid evaluation of fatigue limit in AZ31B magnesium alloy using acoustic emission

“… Previous studies indicated that plastic strain increases with the cycle number, and that strain hardening is completed when the strain gradually decreases towards stability [28,29]. Wang et al observed that the tensile strength of AE31b Mg alloy peaked during the initial stage (almost the first 10,000 cycles) [30], which was caused by strain hardening. In this study, strain hardening of the specimen was completed in the first 10,000 cycles (stage 1 and 2), as shown in Figure 7.…”

“…The amplitudes of the accumulative energy and the specimen's strain increased with loads levels, as revealed in Figure 8. Strain hardening can be attributed to dislocation-precipitate interaction [30]. Therefore, larger load will result in greater strain and more energy dissipation [32].…”