Effect Of Electromagnetic Energy On The Microstructure And Compositional Segregation Of DC-casting Al-Si-Cu-Mg-Ni Piston Alloy

Al-Si-Cu-Mg-Ni piston alloy,the alloy has good fluidity,low density,high strength,corrosion resistance,high wear resistance,high heat resistance and other characteristics,is an indispensable material in the aviation,automotive industry and other fields.With the development of the aerospace and automotive industries,for the life of the car,the requirements continue to improve,the piston is the core component of the car engine,how to improve the mechanical properties of the piston alloy,has become a top priority.Refining the grain can change the performance and service life of the material.Component segregation can affect the mechanical properties of the material,and reducing the component segregation will benefit the subsequent processing of the ingot.Pulsed electromagnetic field is an emerging technology for grain refinement.In this paper,a pulsed electromagnetic energy grain refinement device developed in the group was applied to the semi-continuous casting process of Al-Si-Cu-Mg-Ni piston alloy in a semi-continuous casting line to investigate the effect of electromagnetic energy on the microstructure and composition segregation of Al-Si-Cu-Mg-Ni piston alloy by changing the parameters.The microstructure of Al-Si-Cu-Mg-Ni piston alloy was observed by plasma mass spectrometer for chemical composition detection and field emission electron microscope(FSEM)and optical microscope,and the changes of alloy phase composition and crystal orientation were analyzed by X-ray diffractometer.The experimental results showed that the size of primary Si decreased and the shape factor increased under the effect of electromagnetic energy,and the morphology of primary Si tended to be more rounded,while the size distribution of primary Si was improved and was more in line with normal distribution and uniformly distributed in the matrix;the average size of primary phase ?-Al and the spacing between primary and secondary dendrite arms changed more obviously,the average size of primary phase ?-Al decreased and the spacing between secondary The average size of the primary phase ?-Al decreases and the spacing between the secondary dendritic arms shortens;the observation of the heat-resistant phase in the microstructure shows that the size,distribution and morphology of the heat-resistant phase change under the action of electromagnetic energy.The compositional segregation of Al-Si-Cu-Mg-Ni piston alloy was tested,and after the electromagnetic energy was applied to the melt,the compositional segregation was improved,the local segregation was reduced,and the solute elements were more uniformly distributed.The electromagnetic energy refinement mechanism analysis was carried out.When the pulsed electromagnetic field was applied above the liquid phase line temperature,the electromagnetic energy acted on the atomic groups and reduced the activation energy,resulting in an increase in the number of atomic groups and a decrease in their size,and the electromagnetic energy refinement mechanism was considered to be due to the change of the melt structure by the electromagnetic energy.When the pulsed electromagnetic field parameter was 20 Hz,the average size of primary phase ?-Al in the core was reduced to 24 um,and the average size of ?-Al in the edge tissue was 17 um.The primary dendrite arm spacing of primary phase ?-Al in the core tissue was 60.4 um and the secondary dendrite arm spacing was 13.67 um.The secondary dendrite arm spacing of primary phase ?-Al in the edge tissue was reduced to 7.8 um The composition segregation was improved,and the local segregation of solute elements Si,Cu and Mg was reduced to 0.75%,0.41% and0.59%,respectively.