Effects Of Heat Treatments On The Electrical Conductivity And Mechanical Properties Of ZM51 Magnesium Alloys

In the fields of aerospace,electronic communications,and rail transit,the demand for lightweight electromagnetic shielding structure has become increasingly urgent.Magnesium alloys have low density,high specific strength,compact structure,excellent electrical conductivity and electromagnetic shielding performance.As a potential electromagnetic shielding material,it has attracted much attention.The electromagnetic shielding performance of magnesium alloy is closely related to the change of their electrical conductivity.Therefore,it is of great theoretical reference and engineering application significance to study the conductive properties of magnesium alloy.In this paper,Mg-5 wt.%Zn-1 wt.%Mn(ZM51)magnesium alloys with high specific strength and high thermal conductivity were studied.The effects of solute atoms on the electrical conductivity of Mg-5 wt.%Zn-1 wt.%Mn(ZM51)magnesium alloys were studied,and the effects of solute atom,dislocation and the second phase on the electrical conductivity of ZM51 magnesium alloy were analyzed.The effects of different aging systems on the electrical conductivity and mechanical properties of large section ZM51 magnesium alloys were also summarized.The analytical testing methods used in the experiment include optical microscopy(OM),scanning electron microscopy(SEM),transmission electron microscopy(TEM),X-ray diffraction(XRD),electrical conductivity testing,and mechanical property testing.(1)By preparing the same atomic percentage of Mg-Al,Mg-Zn,Mg-Y binary alloys,it was found that the electrical conductivity of magnesium alloy depended on the atomic radius difference between the solute atom and the matrix atom.The smaller the atomic radius difference is,the smaller the matrix lattice distortion is,which leads to higher electrical conductivity of the alloy.(2)The ZM51 magnesium alloys were treated with homogenization,T5 single aging and two-step aging,T6 single aging and two-step aging treatment.The effects of second phase,dislocation and solute atoms on the electrical conductivity of ZM51 magnesium alloys were investigated.The results show that the electrical conductivity of the alloy is increased after the homogenization treatment.The reason is that Mn atoms are separated from the matrix while the Zn atoms are dissolved in the homogenization process,and the atomic radius difference between Mn and Mg is larger than the atomic radius difference between Zn and Mg,so the precipitation of Mn atoms counteracts the effect of Zn resolution on the electrical conductivity of the alloy.At the same time,it was found that the electrical conductivity of ZM51 magnesium alloy increases first and then keeps stable with the increase of aging time.The high density dislocation accelerates the precipitation of Zn atoms from the matrix,which leads to a higher rate of conductivity increase of the ZM51 alloy after T5 treatment than that of the T6 treatment.During two-step aging,the pre-aged G.P.zone is favorable to the formation of fine dispersed second phases,which can reduce the electrical conductivity of the alloy.(3)The two-stage solution system for industrial production of ZM51 magnesium alloy with large cross-section size was studied and optimized.After peak aging treatment of T5 single aging and two-step aging,T6 single aging and two-step aging treatment,the tensile strength of the alloy is 310 MPa,318 MPa,324 MPa and 341 MPa,respectively,and the electrical conductivity is 18.4 MS/m,18.4 MS/m,18.2 MS/m and 18.2 MS/m,respectively.It shows that after the T6 treatment,ZM51 magnesium alloy has a small decrease in electrical conductivity and the strength is higher than that of the T5 treatment.Moreover,ZM51 magnesium alloy can directly utilize the aluminum alloy production line for large-scale industrial production to improve production efficiency and reduce production costs.