Effect Of Microalloying With Ca And Ce On Microstructure And Stamping Properties Of AZ31 Alloys

Magnesium alloys have received increasing attention due to many advantages that they take on,such as light weight,high specific stiffness and high specific strength.However,their poor formability at room temperature limits their widespread commercial usability.Rare earth(RE)magnesium alloys usually have good formability,but the addition of a large number of RE elements makes the cost of magnesium alloy increase greatly.The development of magnesium alloys with low cost and high formability can effectively promote the application of magnesium alloys.In this study,the effects of Ca content on the microstructure and stamping properties of AZ31 alloys were investigated by adding different Ca contents to AZ31 magnesium alloys.After that,the Mg-3Al-1Zn-0.2Ca alloy with the best formability was selected to explore the rolling and annealing process,and the rolling and annealing process was optimized by the difference in room temperature formability.Finally,the RE element Ce was added to the AZ31 and Mg-3Al-1Zn-0.2Ca alloys to investigate the effect of Ce and/or Ca on the microstructure,formability and mechanical properties of the AZ31 alloy.The main conclusions obtained are as follows:(1)Extruded AZ31 alloy sheets have a strong basal texture.The greater the Ca content,the more fully recrystallized the extruded alloys.Ca element can reduce the number of shear bands and promote dynamic recrystallization during hot rolling.With the increase of Ca content,the strength of the basal texture of the rolled and annealed sheets gradually weakened,the basal texture intensity of Mg-3Al-1Zn-0.2Ca alloy is 3.5,and the basal poles of the Mg-3Al-1Zn-0.12 Ca and Mg-3Al-1Zn-0.2Ca alloy sheets spreading towards TD.With the increase of Ca content,the room temperature formability of AZ31 alloy sheets gradually increased,Erichsen value of Mg-3Al-1Zn-0.2Ca alloy is 6.5 mm,and the anisotropy weakened.The anisotropy of the sheets is related to the distribution of the basal texture.The ? r values of the Mg-3Al-1Zn-0.12 Ca and Mg-3Al-1Zn-0.2Ca alloy sheets are 0.17 and 0.18,respectively.(2)It was found that when the rolling temperature is 450°C or the pass reduction rate is 20%,the alloy sheet has a weaker basal texture,which can improve the room temperature formability of the alloy sheet.In the range of 300 °C ~ 450 °C,the room temperature formability decreases with the increasing annealing temperature.The optimal rolling and annealing technology are 20% reduction rate per pass,rolling temperature 450 °C,and final annealing temperature 300 °C.At this time,the basal texture strength of Mg-3Al-1Zn-0.2Ca sheets is 3.5,and the room temperature Erichsen value is 6.5 mm,which has excellent room temperature formability.(3)Ca and Ce can promote the dynamic recrystallization nucleation of AZ31 magnesium alloys,recrystallize grains of the extruded sheets are more uniform and smaller,thereby weakening the basal texture of the extruded sheets.Ca and Ce can weaken the basal texture of the rolled and annealed sheet,the texture of the alloys with Ca and Ce added is the weakest,and the basal texture intensity is 3.2,and the Ca element also modify the texture distribution of the sheets.The basal texture of the Mg-3Al-1Zn-0.2Ca and Mg-3Al-1Zn-0.2Ce-0.2Ca sheets have a spreading of basal pole towards TD,and the modified texture is mainly due to the change of the slip systems caused by the alloying elements.Ca and Ce decreased the r value and anisotropy of AZ31 sheets.Among them,Mg-3Al-1Zn-0.2Ce-0.2Ca sheets had the lowest r value and the weakest anisotropy,r value was 1.05,and ? r value was 0.04,the reduction of sheet anisotropy is closely related to the modified texture.Ca and Ce have greatly improved the room temperature formability of AZ31 alloy sheets,among which the Erichsen value of Mg-3Al-1Zn-0.2Ce-0.2Ca sheets is the largest.Improvements in room temperature formability of the alloys can be attributed to the modified texture,smaller r values and larger n values.