| Al-Cu-Mn-Zr-V alloy is a kind of high performance cast aluminum alloy with high specific strength and good cutting performance,which is formed by adding Mn,Zr,V and Ti on the basis of Al-Cu alloy.It is widely used as a non-ferrous metal structural material in aviation,aerospace,automotive,defense and medical fields.However,the development and application of Al-Cu-Mn-Zr-V alloy is limited by the inhomogeneous distribution of temperature and flow fields during solidification,resulting in coarse solidification structure and poor overall mechanical properties.Grain refinement is the most effective and direct way to improve the properties of metallic materials,and the mechanical properties of the alloy can be effectively improved by grain refinement.The addition of refining agents to metals using traditional chemical treatment methods introduces foreign elements and risks toxic reactions with existing elements of the alloy.By applying physical fields such as electric pulse,rotating magnetic field,and electric pulse-rotating magnetic field combination to the solidification process of Al-Cu-Mn-Zr-V alloy,it is possible to refine the solidification structure and avoid the introduction of other foreign impurity elements by adding refining agents to the Al-Cu-Mn-Zr-V alloy composed of multiple elements when chemical refinement is used.In this paper,the effects of physical fields such as electric pulse,rotating magnetic field and electric pulse-rotating magnetic field combination on the solidification structure and properties of Al-Cu-Mn-Zr-V alloy were studied,and different physical field treatment processes were compared and analyzed,and the mechanism of refinement of the solidification structure of Al-Cu-Mn-Zr-V alloy by physical field treatment was initially elucidated.The results of the study indicate that.(1)When electrical pulses were applied during the solidification of Al-Cu-Mn-Zr-V alloy,when the pulse current was 200 A,the pulse duty ratio was 10%,and the pulse frequency was 50 Hz,the Al-Cu-Mn-Zr-V alloy had the best refinement effect on the solidification structure after the electrical pulse treatment,and the average grain size was reduced from 140.45 μm to 78.86 μm during the conventional solidification,and the tensile strength and The tensile strength and elongation were 222.0 MPa and 11%,respectively,which were 25.4%and 115.7%higher than those of conventional solidification.Under the action of electric pulse,on the one hand,the gradient distribution of electromagnetic force in the melt forms shear force,which causes the dendrites to break up and form new nuclei during solidification;on the other hand,the electromagnetic wave motion repeatedly compresses the melt,which promotes the solidification of the alloy and increases the subcooling degree to increase the nucleation rate;in addition,the Joule heat effect remelts the solid phase to a certain extent,which inhibits the growth of dendrites and obtains a more uniform solidification structure,reducing the The temperature gradient in the adjacent solid-liquid phase region is reduced.(2)Under the effect of rotating magnetic field,the average grain size of Al-Cu-Mn-Zr-V alloy was reduced from 140.45 μm to 75.49 μin conventional solidification with a magnetic field current of 160 A and a magnetic field frequency of 10 Hz,and the tensile strength and elongation were 243.2 MPa and 11%,which increased by 37.4%and 115.7%,respectively,compared with conventional solidification.The solidification structure was improved and the grain refinement was achieved due to the forced convection effect generated by the rotating magnetic field,which increased the fluidity of the melt,promoted the heat dissipation within the melt,increased the subcooling,and increased the number of nuclei per unit time.(3)The process parameters of the solidification structure of the alloy treated by the compound field were optimized by applying the orthogonal test method with simultaneous application of electric pulse and rotating magnetic field during the solidification of Al-Cu-Mn-Zr-V alloy.With the optimal combination of parameters of 15%pulse duty ratio,50 Hz pulse frequency,150 A pulse current,120 A magnetic field current,and 14 Hz magnetic field frequency,the average grain size of the alloy was reduced to 69.08 μm,and the tensile strength and elongation were 252.2 MPa and 12.1%,respectively.The interaction of the electric pulse and the rotating magnetic field obtains the dual effect of electromagnetic stirring and electromagnetic wave motion,which breaks the growing dendrites and generates new nuclei and improves the nucleation rate,while the fluidity of the melt under the compound field is better,which increases the cooling rate and the subcooling degree is enhanced,so the grain refinement effect is better.(4)Three physical field refinement process after the treatment of the alloy solidification structure refinement effect and mechanical properties have been improved to varying degrees.It was found that the grain refinement effect after the compound field treatment was better than that of the single field treatment,and the mechanical properties of the alloy were improved most significantly after the compound field treatment. |
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