Microstructure And Mechanical Properties Of AZ31 Magnesium Alloy Processed By Pulsed High Magnetic Field

Magnesium alloy is gradually replacing traditional engineering structure materials and has been widely applied in many engineering applications owing to its excellent comprehensive performances.However,due to its hexagonal close packed lattice characteristic,the plastic deformation ability of magnesium alloy is poor,which greatly limits its development.In this paper,based on the magnetoplastic effect,the microstructure and properties of AZ31 magnesium alloy subjected to pulsed high magnetic field and tensile deformation were investigated with the assistance of advanced measurement techniques including X-ray diffraction(XRD),optical microscopy(OM),scanning electronic microscopy(SEM),transmission electronic microscopy(TEM)and backscattering(EBSD).Meanwhile,the mechanical properties were also studied by microhardness test,tensile properties analysis and residual stress measurement.It can be seen from the microstructure of magnesium alloy that magnetoplastic effect reached the best,the dislocation density has increased 69.1% compared with the initial sample,a high flexibility and exhibits network distribution at B = 3T,N = 30.In the presence of pulsed high magnetic field,the spin state of electron between dislocation and pinning obstacle has been changed,which results in the depinning of dislocation,the enhancement of dislocation motion ability and dislocation multiplication.When more dislocations pile up at boundary,it would evolve in sub-grain refining the grains at B = 3T,N = 30,which size is about 4um and has been refined obviously in comparison to that of untreated sample.In the refining process,because the magnetisability of c axis is higher than that of a axis,sub-grain has the orientation rotation due to magnetization work of pulsed magnetic field,and the texture of magnesium alloy has been weakened.The results of mechanical properties analysis show that at B = 3T,N = 30,the tensile strength and elongation of magnesium alloy have been increased synchronously ?Meanwhile,the strength is 233 MPa and elongation is 13.7%,which have been improved by 8.4% and 41.2% respectively compared with that of initial sample.It is analyzed that the network dislocation structure has improved the ductility of materials,fine crystal reinforcing and dispersal reinforcing synchronously improve the material strength.At B = 3T,N = 30,the dimple number increases and it exhibits mixed fracture morphology in comparison to the river pattern characteristics of untreated samples.The residual stress of magnesium alloy firstly increases and then decreases with the increasing of magnetic induction intensity and pulse number,which change tendency is as same as the microhardness.At B = 3T,N = 30,the residual stress reached the minimum of-3MPa and microhardness is 57.2HV,which has been decreased by 106.8% and 11.3% respectively.