Plasticity and microstructure of AZ31 magnesium alloy under coupling action of high pulsed magnetic field and external stress

Abstract

As an h.c.p crystal structure with only a few limited slipping planes, the AZ31 magnesium alloy exhibits a bad plasticity in the presence of external stress. Due to its low density, advanced damping capacity and high ratio strength and rigidity, the magnesium alloy has gradually become the focused and potential structural and functional metallic material in the diverse fields of aerospace, aviation and vehicle transportation, electronic products, etc. Therefore, it is of great importance to improve the process ability of conventional magnetism alloy as AZ31. In the past decades many approaches have been proposed in order to improve the plastic deformation capability. Among these, the diverse physical fields are regarded as the effective methods to improve the comprehensive mechanical properties of metallic materials due to their peculiar heat, force and quantum effects together with the advantageous characteristics of low pollution and high efficiency. In the paper, on the basis of previous researches, a high pulsed magnetic field is introduced into the tensile test to study the influences of magnetic field on the plasticity and microstructure of AZ31 magnesium alloy in order to explore a novel way to enhance the plastic deformation capability of alloy. As for the current experiment, the tensile test of AZ31 magnesium alloy is carried out under the coupling action of high pulsed magnetic field and external stress. The test results are compared with those processed without magnetic field. Several advanced detection methods are utilized to investigate the microstructure including the electron back scattered diffraction, X-ray diffraction and transmission electron microscopy, etc. Besides, the first principle is utilized to calculate the magnetic properties of main precipitates (Mg17Al12).The experimental results show that the tensile strength and elongation of the 3 T sample are increased by 2.2% and 28.7% in comparison to those of the 0 T sample. It highlights that when the high pulsed magnetic field is introduced into the plastic deformation process, the plasticity of the magnesium alloy can be improved without reducing the tensile strength of the material. The action mechanism of magnetic field is analyzed in detail and attributed to the magnetoplasticity effect. The calculation results on the basis of first principle show that the (Mg17Al12) phase is paramagnetic, which is helpful for performing the effect of magnetic field. The magnetic field enhances the flexibility of the dislocation movement and facilitates the proliferation of the dislocation. The dislocation and stress concentrating at the grain boundaries accelerate the formation of recrystallization, which is of great importance to the sub-grain generation and grain refinement that is beneficial to exhibiting the fine grain strengthening and enhancing the strength and toughness of alloy. Meanwhile, during the peculiar tensile process, the magnetic field induces the grain rotation. The newborn fine grains along the non-basal face weaken the (0001) basal texture of magnesium alloy. The characteristic of the texture structure is helpful for improving the plastic deformation capacity of AZ31 alloy. The plastic deformation under high magnetic field is regarded as an advanced way to improve the plasticities of similar nonmagnetic metallic materials such as aluminum, titanium and copper alloys and their composites.