Influence of high frequency vibration on deep drawing process of AZ31 sheet at room temperature

Abstract

Quasi-ultrasonic vibration with a frequency of 15 kHz and a maximum output of 2 kW was imposed on the deep drawing process of AZ31 magnesium alloy sheet at room temperature, in order to reveal the effect of high frequency vibration on deformation behavior of AZ31 during the process. From the drawn results and the observation of the microstructure within the large deformation area, high frequency vibration has a great influence on the formability, the forming load and the failure mode of AZ31 sheet during the deep drawing process; the influence is a comprehensive result of so-called “volume effect” and “surface effect”, and relies on the vibrating amplitude. Total forming load decreased significantly as soon as the vibration superimposed. According to the tensile test results of AZ31 bars under ultrasonic vibration, the formability of AZ31 sheet increases firstly with the increase of stimulating energy, then decreases and finally becomes brittle. Under the combined influence of “surface effect” and the “softening” in the “volume effect” near the relative low amplitude of 25%A in the experiment (A is the maximum amplitude), the formability of AZ31 reaches the largest value, and the samples possess the same distribution trend of cracks as those added with lubricating oil. With the increase of excitation energy, the “volume effect” gradually becomes apparent, and finally the “hardening” of the “volume effect” occupies a dominant position.