Study On Electromagnetic Shielding And Mechanical Properties Of Mg-Zn-Y-Ce-Zr Magnesium Alloys

Electromagnetic waves generated by electronic equipment are full of living and working space with fasting development of electronic products and frequently using of digital system.Excessive electromagnetic radiation causes electromagnetic pollution.Electromagnetic shielding is more important than before as one of the most effective methods of protection.Now electromagnetic shielding has become the research hotpot of each country.The development of high-performance shielding material is a very important part.Magnesium?Mg?and its alloys are the lightest environmentally friendly engineering structural materials today,and they are in good electromagnetic shielding properties.Mg and its alloys are the potential electromagnetic shielding materials.However,the use of Mg alloys in terms of special function and mechanical properties is often incompatible.And the application of Mg alloys is limit because of their low absolute strength.Therefore,the development of high-performance Mg alloys is the premise of supporting its large-scale applications.We systematically studied the influencing factors and control conditions of shielding and mechanical properties of Mg alloys.The controling method of shielding and mechanical properties was developed based on optimization selection of alloys'composition and heat treatment.Shielding effectiveness?SE?and mechanical properties of Mg alloys is expected synergistically improved.Promoting the integration of special functional and mechanical properties of Mg alloys is of great significance for industrial applications.In this work,we have added Ytrrium?Y?and Cerium?Ce?to Mg-Zn-Zr alloys and successfully developed Mg-5Zn-xY-1Ce-0.5Zr,Mg-6Zn-xY-0.5Ce-0.4Zr and Mg-2Zn-xY-0.5Ce-0.4Zr alloys with diffirent phase type through controlling Ce contents and changing Zn/Y ratio.And we have studied SE and mechanical properties of the three series alloys in diffirent deformation conditions.We also studied the effect of Y contents on the microstructure,SE and mechanical properties of the three series alloys.We summarized the important methods that how to design Mg alloys with excellent SE and mechanical properties at the same time.The important results are following.?1?The second phases in Mg-5Zn-xY-1Ce-0.5Zr alloys are Mg_1.5Zn_9.5Ce₃,Mg₃Zn₃Y₂?W?,Zr riched phase.The extruded Mg-5Zn-xY-1Ce-0.5Zr sheets are in good SE properties.Mg-5Zn-1Y-1Ce-0.5Zr and Mg-5Zn-2Y-1Ce-0.5Zr alloys are in highest SE values which reach 76-118dB and 79-118dB at the whole frequency,respectively.The second phase with high density and diffuse distribution is an important factor in improving the SE.In addition,the presence of the base texture improves surface reflection loss and improves the total SE finally.?2?The extruded Mg-5Zn-xY-1Ce-0.5Zr bars are in excellent strength.The strength and ductility of the alloys are improved after aging.Aged Mg-5Zn-0.5Y-1Ce-0.5Zr alloy has the yield strength of more than 400 MPa and elongation of 7.1%.The microstructure contains dynamic recrystallized?DRXed?and unrecrystallized?unDRXes?regions.The average DRXed grain size is about 1?m.Dynamic precipitation happens during hot extrusion.There are more precipitates after aging.Numerous precipitaes and intensive texture make a great contribution to strength improvement.?3?The second phases in Mg-6Zn-xY-0.5Ce-0.4Zr alloys are Mg_1.5Zn_9.5Ce₃,Mg₃Zn₆Y?I phase?,W-phase,and Zr-riched phases.The microstructure of extruded sheets contains DRXed and unDRXed regions.The DRX mechanism is particle stimulate nucleation?PSN?.Dymanic precipitation happens during hot extrusion,and we can see many nano-scale precipitates in Mg matrix.Mg-6Zn-xY-0.5Ce-0.4Zr sheets have excellent shielding properties and SE value enhances with Y contents.Mg-6Zn-1.5Y-0.5Ce-0.4Zr alloy is in the highest SE value which arrives 86-112dB at the whole frequence.At the same time,Mg-6Zn-xY-0.5Ce-0.4Zr sheets possess good mechanical property.Mg-6Zn-0.5Y-0.5Ce-0.4Zr and Mg-6Zn-1Y-0.5Ce-0.4Zr alloys are both in superior shielding and mechanical properties.?4?The microstructure of extruded Mg-6Zn-xY-0.5Ce-0.4Zr bars include also DRXed and unDRXed regions.The DRXed mechanism is PSN and the the number of unDRXed regions decrease with Y contents.Mg-6Zn-xY-0.5Ce-0.4Zr bars are in excellent yield strength,especially for better elongation compared with Mg-5Zn-xY-1Ce-0.5Zr bars with the reason of weakened texture.The alloys with0.2-1 wt.%Y contents possess superior mechanical property.The strength improves and elongation keeps well after aging.The aged Mg-6Zn-1Y-0.5Ce-0.4Zr is in superior strength and elongation among these alloys.Its yield strength,ultimate tensile strength and elongation is 371 MPa,409 MPa and 10%,respectively.Grain refinement and precipitation strengthening are the main reason for high strength.In a word,Mg-6Zn-1Y-0.5Ce-0.4Zr alloy is both in excellent shielding and mechanical properties.?5?The shape of long period stacking ordered?LPSO?phase of cast Mg-2Zn-xY-0.5Ce-0.4Zr is in lamellar and along grain boundary and junction of grain boundary.The orientation of LPSO phases is ramdom and the structure of LPSO phases is belong to 18R.After homogenization some lamller structure appears inside or cross grains.The LPSO phases are in deformed,bended and in blocky shape in Mg matrix after hot extrusion.Y is mainly present in three forms in the Mg-2Zn-xY-0.5Ce-0.4Zr alloy.It combines with Mg and zinc?Zn?to form an LPSO phase,forms a second phase containing a very high Y content,and solid solution in Mg matrix.The relative conductivity of Mg-2Zn-xY-0.5Ce-0.4Zr alloys is lower than15%IACS and no significant improvement.We simulated the reflection loss SE of this alloy and other Mg alloys,and the calculated value is lower than that of commercial ZK60 alloy,Mg-5Zn-xY-1Ce-0.5Zr series and Mg-6Zn-xY-0.5Ce-0.4Zr series.As the Y content increases,the solid solubility in?-Mg matrix increases,and the lattice distortion becomes more serious.The increase in the solid solubility of Y in?-Mg matrix causes the relative conductivity to gradually decrease,which reduces the reflection loss.In addition,the coarsing LPSO phase is harm for shielding loss.The total SE decreases in the end.The strength of extruded Mg-2Zn-xY-0.5Ce-0.4Zr alloys enhanceswithYcontentswhileelongationisin oppositetrend.Mg-2Zn-6Y-0.5Ce-0.4Zr alloy has better comprehensive performance compared with others.Its yield strength,ultimate tensile strength and elongation is 229 MPa,362 MPa and 17.9%,respectively.