| As the lightest structural material in the 21st century,magnesium alloys have excellent effect on reducing weight,high specific strength and stiffness,excellent biocompatibility and degradability,so they have been increasingly applied to various fields that closely related to our daily life.However,compared with the traditional steel,Al,Ti and their alloys,magnesium and their alloys show lower strength.Meanwhile,the crystal structure of hexagonal close-packed makes them difficult to initiate the non-basal slip in the various deformation processes at low temperature,which leads to the poor ductility and high preparation cost of magnesium alloys.Therefore,this paper takes the extruded Mg-1.03Ca-0.47 Mn magnesium alloy sheets as the research object and takes the fabrication of high strength-ductility balance and low cost Mg-1.03Ca-0.47 Mn magnesium alloy sheets as the research target,and which will provide research references for the subsequent fabrication of high strength-ductility balance and low cost magnesium alloy sheets by researching the influence of rolling and annealing processes on the evolution of microstructure and mechanical properties of the sheets.The results of the study showed that:(1)Rolling could refine the grains of the original extruded sheets and improved the strength,but it also led to the increase of the density of dislocation and strain,which led the basal orientation and(0001)basal texture to been strengthened and the elongation to been reduced.(2)The cool rollers rolling promoted the non-basal slip,which led to the start of dynamic recrystallization.But the degree of dynamic recrystallization was low and the average grain size,yield strength and ultimate tensile strength were only 8.3μm,242 MPa and 253 MPa,and elongation was decreased to 6.9%,4.4% with the increase of total rolling reduction,respectively.(3)The average grain size to be further refined to 6.1μm by the warm rollers rolling,and the yield strength and ultimate tensile strength were improved 248 MPa,272MPa respectively.The density of(0001)basal texture was improved 16.02 and the elongation was reduced to 1.6%.The low temperature of warm rollers rolling inhibited the non-basal slip,dynamic recrystallization and can transform the dynamic recrystallization mechanism of cool rollers rolling into the mechanism of deformation-induced grain refinement which led the migration of grain boundaries to be limited,the low angle grain boundaries to be increased and the basal orientation to be strengthened.(4)The temperature-step-down rolling guided the dynamic recrystallization mechanism and deformation-induced grain refinement mechanism coexist,basal slip and non-basal slip coexist.The average of grain size was refined to 3.2μm,the yield strength and ultimate tensile strength were further improved to288 MPa,309MPa.The(0001)double peak basal texture was formed which resulted in the density of texture decreasing to 8.43.Compared with the 1.6% of high strength sheet in warm rollers rolling,the elongation of temperature-step-down rolling sheet was improved to 3.3%.Elevating the strength at the same time,the elongation was improved more than one times.(5)Annealing can promote the occurrence of static recrystallization and significantly improves the mechanical properties of magnesium alloy sheets.After annealing at the sheets of fabricated by low temperature or big total rolling reduction,the grains barely grew up.Therefore,after annealing,the density of dislocation and basal orientation of temperature-step-down rolling sheets were weakened and formed(0001)weak double peak basal texture.Finally,the Mg-1.03Ca-0.47 Mn magnesium alloy sheet with strength-ductility balance was successfully prepared.The yield strength,ultimate tensile strength and elongation are up to 256 MPa,305MPa and 13.1%,respectively. |
