Effect Of Pulsed Magnetic Field On Microstructure And Properties Of Pure Al And Al-23%Si Alloys

In the manufacture of materials and modern metallurgy engineering,applied physical fields control methods have a broad application prospect.It is the interaction between the physical fields and metal,to refine the solidification structure,improve the metallurgical quality and mechanical properties of materials.Physical field in grain refinement has a great advantage.It is simple to be operated,no pollution.It is a truly green approach.Application of pulsed magnetic field technology in this field is still in its infancy.In this paper,the solidification structure of pure aluminum and Al-23%Si alloy under pulsed magnetic field was studied.Unlike previous only differentiated by the solid and liquid state,more detailed periods of the solidification process are divided into the liquid,the initial core forming,the grain growth,the solidification stage.The experiment is to explore the optimum temperature range of pulsed magnetic field,to support for the study of metal solidification behavior under pulsed magnetic field.Through the study of aluminum solidification microstructure and properties,under the pulsed magnetic field,we can know:Applying a pulse magnetic field in the liquid,the solidification structure of pure aluminum has not changed.Applying a pulsed magnetic field in the nucleation stage,the solidification structure of pure aluminum has some refinement.The refining effect of pulsed magnetic field is the best in the solidification stage.At 650-630?applying a pulse magnetic field,when the discharge voltage is 2kV,3kV,the refining effect of pulsed magnetic field in 20s is better than 40s.When the discharge voltage is 5kV,the refining effect of pulsed magnetic field in 40s is better.Because of the thermal effect of the magnetic field the refined grain has grown.The sample hardness value of the pulse magnetic field treatment is significantly higher than the hardness without pulse magnetic field treatment.The hardness in solidification stage is the highest.Through the study of Al-23%Si alloy solidification microstructure and properties,under the pulsed magnetic field,we can know:The primary Si in the edge of solidification Structure of untreated Al-23%Si alloy is coarse,elongated strip,and unevenly distributed.Under the effect of pulsed magnetic fields,the primary Si is small,blocky.With the discharge voltage increases,the primary Si is finer and more uniform.Applying a pulse magnetic field in the early solidification,the refining effect of Al-23%Si alloy Solidification Structure is significantly better than medium-term.In the late stages of solidification,the refining effect of pulsed magnetic field to the primary Si is best.Magnetic field can refine the elongated primary Si to the blocks,but can't improve the segregation phenomenon of the organization.In short,in order to achieve the best refining effect of pulsed magnetic field on Al-23%Si alloy,it is necessary to continue applying a pulsed magnetic field from the gestation period to the end of solidification.Hardness of the sample by the pulsed magnetic field treatment was significantly better than untreated.In the same temperature range,with the discharge voltage increases,the hardness value of the sample increases.