Research On Rolling Process Of ZK60 Magnesium Alloy Sheet

As the lightest metal material in the 21 st century,the magnesium alloy find more and more attention and applications because of its low density,high specific strength and easy recovery.ZK60 is a typical high-strength magnesium alloy,but it has poor rolling performance as it is easily formed crystal compounds of MgZn phase in the casting process,resulting seriously hot cracking and work hardening in hot rolling process.In this paper,the homemade ZK60 magnesium alloy is the study object,through the deformation process of homogenizing,hot rolling,cold rolling and annealing,studying the influence of rolling temperature,reduction in pass,rolling made and annealing on microstructure,texture and mechanical properties.Several conclusions can be summarized as follows:(1)As the rolling temperature elevated,non-base slip system was stated and resulted in the dynamic recrystallization increasing.The minimum average grain size is 9.35μm,and the(0002)base texture is the weakest at 400℃.(2)The addition of reduction in pass will raise the density of dislocation,and promote the dynamic recrystallization increasing.Therefore the average grain size decreases and(0002)base texture increase.But large deformation will reduce the uniformity which affecting the mechanical properties.(3)The second twin will be generated in cross rolling,and the intergranular deformation will be promoted by launch of non-basal slip system.Which result in increasing of dynamic recrystallization and grain refinement.Grain refinement conducive to grain rotating and crystal territories mobile.The change of rolling direction will forced grain offsetting from original rolling direction to TD direction,eventually the(0002)basal texture intensity dropped to 7.12 from 8.61,and the type of texture transformed from(0001)[0(?)10](0 °,120 °)to(0001)[(?)(?)30](0 °,139.11 °)and((?)105)[2(?)11](20.16 °,18.02 °,60 °).The ductility of alloy improved by grain refinement and texture weaken.(4)As the annealing temperature raised,the completion time of static recrystallization will reduce,and the mechanical properties of alloy will improve.But the excessive annealing temperature will cause the grain coarsening,which leading to the strength and ductility reduced.As the annealing time extended,the strength and ductility of alloy will increase firstly and decrease subsequently.While reasonable annealing process will reduce the intensity of texture.Therefore the final annealing process is 340℃×1h.(5)The static recrystallization of annealing process in alloys was characterized by Vickers-hardness test method,and gain the completion time of static recrystallization.Finally we calculate the activation energy of 20% reduction in ZK60 magnesium alloy is 58.8KJ/mol and get an equation between the volume fraction of static recrystallization and annealing time under different temperatures.