Research On The Microstructure And Mechanical Properties Of Variable-plane-rolled Mg-3Al-1Zn Alloy

Magnesium alloy is a light structural material with a bright development prospect. But magnesium alloys made by traditional plastic machining have many disadvantages, such as low strength, low plasticity and mechanical anisotropy. In order to make magnesium alloys have a large application in industries, it is particularly important to make a new plastic processing technology and improve mechanical properties.In this paper, AZ31 magnesium alloys were processed by variable-plane rolling, cooling variable-plane rolling and variable-plane sheet rolling. The evolved microstructures were observed by optical microscopy, transmission electron microscopy (TEM) and X-ray diffraction (XRD). Uniaxial tensile tests and uniaxial compression tests were carried out at room temperature to analysis the change of mechanical properties after deformation. And the influence of microstructures on mechanical properties was analyzed by combining the microstructures and mechanical properties. The conclusions are as follows:(1) The microstructures of variable-plane-rolled AZ31 magnesium alloy are changed obviously. Dynamic recrystallization occurs during deformation. Grain size is refined and homogeneous. Dislocation density increases and the dislocations form many dislocation cells around grain boundaries or in grains. The number of twins is increasing. And the thickness of twins can be refined to nano-scale. Grain orientation and texture evolution are cvclic varied. Strong basal texture disappears.(2) The mechanical properties of variable-plane-rolled AZ31 magnesium alloy are enhanced significantly. Yield strength and elongation are increased. Beside, the tension and compression asymmetry is improved a lot. Especially in the specimen of 8 pass variable-plane-rolled AZ31 magnesium alloy, the yield strength can reach 275MPa, nearly 50% higher than the initial extruded specimen.(3) AZ31 magnesium alloy processed by cooling variable-plane rolling has a lower strength and a significantly improved elongation. With the reducing of deformation temperature, grains can’t be further refined by dynamic recrystallization. In addition, most of the basal poles are clearly away from the normal direction towards the transverse direction by 35°. So the strength is reduced. At the same time, because of the increased twins and diffuse texture, the elongation has improved significantly.(4) Variable-plane-sheet-rolled AZ31 magnesium alloy has excellent mechanical properties. The elongation is increased. Meanwhile, the yield strength is 60MPa higher than the initial extruded AZ31 magnesium alloy. Furthermore, the texture is different from traditional rolling. So the mechanical anisotropy of variable-plane-sheet-rolled AZ31 magnesium alloy is special. The mechanical properties in rolling direction are best.