| Aluminum alloy is widely used in remote control technology,aerospace technology,chemical industry and portable electronic equipment and other fields.In order to meet the requirements of improving the performance of aluminum alloy,various refining techniques of aluminum alloy have been developed rapidly and have broad application prospects.In this paper,the effects of refiner,rotating magnetic field and the combined treatment of refiner and rotating magnetic field on solidification process,microstructure and mechanical properties of ZL101 aluminum alloy and Al-5Cu alloy were investigated.The quantitative differences of grain size,mechanical properties and metallographic structure between refined alloy melt and untreated alloy melt with refiner,rotating magnetic field,refiner and rotating magnetic field were compared and analyzed to reveal the refinement mechanism of the three.The aim is to seek the optimal parameters of chemical and physical composite refining treatment and optimize the composite refining process in order to obtain better refining results.The solidification microstructure and mechanical properties of ZL101 aluminum alloy were changed by Al-3B refiner,rotating magnetic field and Al-3B refiner combined with rotating magnetic field.The results show that the optimal refining effect is achieved when the B content reaches 0.06 wt.%.The average grain size of α(Al)decreases from 157.8 μm without refiner to 122.4 μm,the tensile strength and elongation increase by 9.4% and 34.9%,respectively,and the hardness of Vickers increases by 12.9%.The refining mechanism of Al-3B refiner treatment of ZL101 aluminum alloy is that after the addition of Al-3B refiner,heterogeneous nucleation particles are added in the alloy melt,which promotes the nucleation of α(Al),significantly improves the nucleation rate,and thus refines the alloy grains.When the rotating magnetic field parameter 80 A+8 Hz is applied to the melt of ZL101 aluminum alloy,the average grain diameter of α(Al)is reduced to 118.7 μm,the tensile strength and elongation are increased by 10.5% and 37.2%,respectively,and the hardness of Vickers is increased by 26.6%.The refining mechanism of applying rotating magnetic field to ZL101 aluminum alloy melt is that the electromagnetic force drives the melt to break dendrites and increase the nucleation rate.At the same time,under the action of rotating magnetic field,the melt heat dissipation is accelerated,the cooling rate is accelerated,the solidification time is shortened,the formation of columnar crystals is restricted,and the alloy grains are refined.The best parameters of Al-3B combined with rotating magnetic field for ZL101 aluminum alloy melt are: B addition of 0.06 wt.% and rotating magnetic field of 80 A+8 Hz,average grain size decreased to 115.1 μm,tensile strength increased by 11.0%,elongation increased by 41.8% and Vickers hardness increased by 27.8%.The solidification and cooling curves,microstructure and mechanical properties of Al-5Cu alloy treated with Al-5Ti-0.2C refiner,rotating magnetic field and Al-5Ti-0.2C refiner combined with rotating magnetic field have different degrees of change.The results show that the melt refining effect of Al-5Cu alloy with 1.0 wt.%Al-5Ti-0.2C refiner is the best,the average grain size of α(Al)decreases from 158.0 μm to 137.0 μm,the tensile strength and elongation increase by 10.0% and 20.4%,respectively,and the hardness of Vickers increases by 44.9%.Al-5Ti-0.2C refiner generates Ti C particles,which have stable properties and can be effectively used as nucleating particles,thus increasing heterogeneous nucleation,improving melt α(Al)nucleation rate and refining grains.When the magnetic field parameter 120 A+8 Hz is applied to Al-5Cu alloy,the average grain size decreases to 127.3 μm,the tensile strength and elongation increase by14.9% and 23.6%,respectively,and the Vickers hardness increase by 47.0%.The rotating magnetic field generates electromagnetic force,which makes the distribution of tissue even,cuts off dendrites by forced convection,inhibits the growth of crystal nuclei,and increases the nucleation rate.The best refining process of Al-5Cu alloy is 1.0wt.%Al-5Ti-0.2C refiner combined with 120 A+8 Hz rotating magnetic field.The average grain size is reduced to 109.3 μm,the tensile strength is increased by 25.3%,the elongation is increased by 40.9%,and the hardness of Vickers is increased by49.8%. |
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