Research On Dynamic Recrystallization, Texture And Mechanical Properties Of Pure Mg During Warm Rolling And Cold Drawing

Due to their low strength and poor ductility pure magnesium can not be used as structural materials, usually they are used as raw materials and functional Materials. Nowadays, there are very few reports on plastic processing and plastic deformation of pure magnesium, especially study about deformation from30%to80%is almost blank. As the basis of the plastic deformation of magnesium alloy, plastic deformation of pure magnesium has an important academic value. Deformation of pure magnesium studied in this article has important significance for filling large plastic deformation of pure magnesium and plastic processing of magnesium alloys. In this paper the experimental methods are hot-rolling and cold-drawing; it has the more direct significance for magnesium and magnesium alloys production.In this paper, hot rolling process was used to study the hot deformation of pure magnesium. Effect of rolling reduction and rolling temperature on grain size, mechanical properties, texture and dynamic recrystallization was study on the basis of the experimental results. Pure Mg sheets with different grain size from14μm to40μm were obtained by controlling the rolling reduction and rolling temperature. At the same time a very large rolling reduction of80%was realized by one pass rolling. After hot rolling, tensile strength, yield strength and elongation of the as-rolled sheets were improved from110MPa,40MPa and4%to250MPa,170MPa and12%, respectively. Due to the intensive grain orientation and larger grain size, the as-rolled pure magnesium sheets showed significant anisotropy. Effect of the factors mentioned above on mechanical anisotropy was discussed in detail in this article. From the experimental results in this article, improving the degree of dynamic recrystallization and grain size refinement is the most effective way to control the anisotropy of as-rolled sheets. Ultimately based on the basis of a large number of experimental data, the dynamic schematic sketch of grain size versus rolling temperature and rolling temperature was established.In this paper, cumulative cold drawing process as used to study cold plastic deformation of pure magnesium. Pure Mg wires with diameter of Φ2mm were obtained by hot drawing and annealing, their yield strength and tensile strength was154Mpa and231MPa respectively. Severe plastic deformation of99%was obtained by multiple-pass drawing with small deformation per pass. Due to their low working hardening rate, pure Mg wires can be drawn fro Φ2mm to Φ0.2mm without any annealing treatment. A series of investigations were discussed such as the plasticity mechanism, the work hardening behaviors and the deformation texture evolution with deformation by means of optical microscopy (OM), transmission electron microscopy (TEM), X-ray diffraction, electron back scatter diffraction (EBSD), microhardness(HV) and tensile tests. There are a great deal of parallel shear bands and{1012} twinning in the microstructures when the area reduction is smaller than50%, and the number of the parallel shear bands and twinning increase with the cumulative area reduction increasing. When the area reduction exceeds50%, the number of the parallel shear bands and twinning begin to decrease. When the area reduction exceeds70%wide parallel shear bands and twinning almost disappeared, the microstructure is composed of large recrystallized grains. The microhardness and the tensile strengths, i.e. yield strengths (YS) and ultimate tensile strengths (UTS) increase with increasing cumulative area reduction at<30%, while opposite for ductilities. With the cold drawing process keeping on, the microhardness, the tensile strengths and the ductilities of the as-drawn wires had not obviously changed. This phenomenon is very common during hot deformation due to dynamic recovery (DRV) and DRX but it is very peculiar in cold deformation. Continuous dynamic recrystallization of pure magnesium at room temperature was first discovered in this article. This phenomenon was discussed in detail on basis of experimental data. Continuous dynamic recrystallization of pure magnesium at room temperature was mainly due to the material properties of pure magnesium and their strong fiber texture.