Influence Of Extrusion Deformation And T5-Treatment On Electromagnetic Shielding Property Of Rare Earth Magnesium Alloy

Rare earth magnesium alloy with its low density,high strength and good heat resistance,has a broad application prospect in linghtweight field.Magnesium alloy shows a good electromagnetic shielding property.While recent studies on the electromagnetic shielding property of magnesium alloy are mainly focused on AZ and ZK category,studies on rare earth magnesium alloy are not common.In order to study the effect of extrusion deformation degrees and T5 heat treatment on electromagnetic shielding property of the Mg-13Gd-4Y-2Zn-0.5Zr magnesium alloy,this paper analyzes and summarizes the relationship between the microstructure evolution in the process of extrusion deformation and ageing heat treatment and the change of alloy electromagnetic shielding property by combining material testing methods including OM,SEM,EDS and XRD based on shielding property tests.The main conclusions are as follows:The as-cast Mg-13Gd-4Y-2Zn-0.5Zr magnesium alloy has an excellent electromagnetic shielding property,and its electromagnetic shielding effectiveness is 86~107dB within the range of 30~1500MHz.As the frequency raises,the electromagnetic shielding effectiveness of as-cast Mg-13Gd-4Y-2Zn-0.5Zr magnesium alloy shows a decreasing trend because the penetrating power of electromagnetic wave becomes stronger.However,the electromagnetic shielding effectiveness of as-cast 7A04 aluminium alloy is 71~107dB,and the as-cast 2A12 aluminium alloy is 71~107dB within the range of 30~1500MHz.In the process of hot extrusion deformation,the electromagnetic shielding effectiveness of Mg-13Gd-4Y-2Zn-0.5Zr magnesium alloy is improving with the increase of extrusion degree.When the deformation degree reaches 80%,its electromagnetic shielding effectiveness is 93~107dB within the range of 30~1500MHz.Mg-13Gd-4Y-2Zn-0.5Zrmagnesium alloy grains are gradually refined as the extrusion degree increases,which leads to a continuous increase of the grain boundary density inside the rare earth magnesium alloy and a higher possibility of refraction and reflection of electromagnetic waves transmitted inside the alloy,thus increasing the absorption attenuation and multiple reflection attenuation of electromagnetic wave inside the alloy.In addition,the gradual toughness of boundary interface structure also contributes to the increase of reflection loss inside the alloy during hot extrusion deformation.When the as-extruded alloy is given T5 heat treatment,its electromagnetic shielding effectiveness increases as time prolongs,yet it does not change monotonously as time goes by.The electromagnetic shielding property of as-extruded Mg-13Gd-4Y-2Zn-0.5Zr magnesium alloy is best when aged at 225 ? for 24h(peak-aged),and the electromagnetic shielding effectiveness reaches 96~107dB within testing frequency range.It is mainly because that a large amount of dispersed second phase Mg5(GdY)are percipitated,which increases the conductivity of the Mg-13Gd-4Y-2Zn-0.5Zr magnesium alloy so that increases the reflection attenuation and absorption attenuation.In addition,the second phase Mg5(GdY)increases the phase boundary density inside alloy,thus increases the multiple reflection attenuation.However,as the ageing time increases,the second phase Mg5(GdY)remarkably gets coarse and a portion of grains grow up,which decreases phase boundary density and grain boundary density inside the alloy,consequently reducing the multiple reflection attenuation inside the alloy.