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In-situ fabrication of functionally graded Al/Mg 2 Si by electromagnetic separation

2 nd Sino-Germany Workshop on Electromagnetic Processing of Materials. In-situ fabrication of functionally graded Al/Mg 2 Si by electromagnetic separation. Li Jianguo lijg@sjtu.edu.cn. School of Materials Science and Engineering, Shanghai Jiaotong University, Shanghai 200030, China.

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In-situ fabrication of functionally graded Al/Mg 2 Si by electromagnetic separation

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  1. 2nd Sino-Germany Workshop on Electromagnetic Processing of Materials In-situ fabrication of functionally graded Al/Mg2Si by electromagnetic separation Li Jianguo lijg@sjtu.edu.cn School of Materials Science and Engineering, Shanghai Jiaotong University, Shanghai 200030, China

  2. Outline: 1. Motivation 2. Principle of the process 3. Experiments and results 4. Summary

  3. Motivation The in-situ Al-Mg2Si composites have great potential applications in the automotive and aerospace industries due to their excellent properties. 1.Problems:Hard and fragile primary phases (eg. Mg2Si in Al-Mg-Si) may harmful to mechanical properties 2.Solution:Gradient distributed from the surface to the center—Functionally graded materials(FGMs).

  4. The process of FGMs by EMS The process of in-situ FGMs by electromagnetic separation (EMS) method is recently proposed by our laboratory. It produces the in-situ FGMs using usual casting under electromagnetic field by one-step. So it lower the production cost. And it can produce the thermodynamically stable systems by in-situ nucleation and growth of the reinforcing particles from the parent melt.

  5. B I Primary particles B I Movement direction Melt Particle Casting mould Melt Electromagnetic forces Electromagnetic Archimedes forces Principle of the process Principle of the process of in-situ FGMs by Electromagnetic Separation method

  6. Movement analysis of particle • Electromagnetic Archimedes force acting on a spherical primary particle can be written: (1) • The buoyant force due to gravity imposed on the primary particle is stated as: (2)

  7. The motion drag force of the primary particles in the molten metalis expressed as: (3) • The terminal migration velocity of primary particleas: • When these forces are in the balance: (4) (5)

  8. CD is the drag coefficient, which is related to the Reynolds number . with laminar flow, where v is the velocity of the primary particle and the viscosity of the melt. ( 6 ) And when the mode of the movement is transition flow , ( 7 )

  9. Experiments and results • Equipments of experiment • Effects of Element Ti • Effects of process parameters

  10. DC Power Anode Cathode Casting gate Upper mould Electromagnet S Molten metal Lower mould Casting mould N (b) (a) Equipment Schematic of equipments used in the process of FGMs by EMS method: ( a ) Top view of the equipments, ( b ) Front view of the equipments.

  11. (c) 0.5mm 0.5mm (c) 0.5mm (b) Effects of element Ti on Microstructures of particle packed region Process parameters: Pouring temperature: 850oC Mould temperature: 400oC Electromagnetic force: 5×104 N/m3 Composition: Al-15Mg2Si –5Si Composition: Al-15Mg2Si –5Si-4Ti

  12. (a) β (b) α β δ 50μm 50μm Microstructures at higher magnification of Al-15Mg2Si –5Si-4Ti samples • β is Al3Ti • δ is a kind of Al-Si-Ti ternary intermetallic compounds, and composition is 65.12at.%Al-13.47at.%Si-21.41at.%Ti

  13. Microstructures of in-situ Al/MgSi FGMs by EMS Method I B (b) (a) (e) (c) (d) 30mm 0.5mm 0.5mm 0.2mm 0.2mm 0.5mm A B C D E 20mm Process parameters: Pouring temperature: 850oC Mould temperature of : 400oC Electromagnetic force: 5×104 N/m3 Composition: Al-15Mg2Si –5Si-4Ti

  14. (a) (b) (c) 0.5mm 0.5mm 0.5mm Effects of the electromagnetic force on particle distributions 5×104 N/m3 3×104 N/m3 1×104 N/m3 Microstructures of upper side in the samples

  15. Movement time of particles for unit distance (1mm) vs the electromagnetic force

  16. Effects of mould temperature on particle distribution (b) (a) (c) 0.5mm 0.5mm 0.5mm 600oC 400oC 200oC Microstructures of upper side in the samples

  17. (a) (b) (c) 0.5mm 0.5mm 0.5mm Effects of pouring temperature on the particle distributions 850oC 800oC 750oC Microstructures of upper side in the samples

  18. Cooling curves of melt Effects of mould temperature Effects of Pouring temperature

  19. (c) (a) (b) 0.5mm 0.5mm 0.5mm Effects of the composition on particle distributions Al-15Mg2Si-5Si-4Ti Al-20Mg2Si-5Si-3.75Ti Al-25Mg2Si-5Si-3.5Ti Microstructures of upper side in the samples

  20. Summary 1. In-situ Al/Mg2Si FGMs was successfully prepared by EMS method. 2. Additional element Ti can prevent primary Mg2Si particles from forming the particle clusters. 3. There exists a critical value of electromagnetic force, and the In-situ Al/Mg2Si FGMs can be prepared by EMS method only when the electromagnetic force is beyond it. 4. Increasing of the electromagnetic force and the content of Mg2Si and decreasing of the solidification rate can make the particle volume fraction of the particle packed region and the gradient of particle distributions increase.

  21. Acknowledgements: The work is supported by the National Natural Science Foundation of China. We express our sincere thanks for their financial support.

  22. The end Thank you!

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