Abstract: There are differences in the mechanical properties of magnesium alloys at different loading rates, in order to explore the relationship between cyclic frequency and ratcheting strain, cyclic experiments under stress control were carried out on extruded AZ31B magnesium alloys to study the effect of frequency on the ratcheting strain of magnesium alloys and its evolution process. In this paper, the cyclic deformation process of magnesium alloys at fre-quencies of 1.0Hz, 2.0Hz and 5.0Hz are discussed respectively, and the results show that: there is an obvious ratchet-ing effect during cyclic deformation of AZ31B extruded magnesium alloys, and the relationship between the ratcheting strain and frequency under the same average stress is not monotonic, and the value of the ratcheting strain at 5.0Hz is in the range between 1.0Hz and 2.0Hz. This is due to the fact that the contribution of twinning to the cumulative strain is greater at high frequency at 5.0Hz, twinning-de-twinning is more pronounced, and the ratcheting strain is maximum as the twinning mechanism accounts for a greater proportion of the hardening rate is lower compared to 1.0Hz vs. 2.0Hz. At different frequencies, the ratcheting strain increases rapidly in the pre-cycle period and stabilizes after a certain number of cycles.

Key words: Frequency, ratcheting behavior, fatigue, stress-controlled, twinning mechanism