P.A. Nikrityuk, K. Eckert, R. Grundmann Institute for Aerospace Engineering,

NUMERICAL STUDY OF THE INFLUENCE OF AN APPLIED ELECTRICAL POTENTIAL ON THE

SOLIDIIFCATION OF A BINARY METAL ALLOY

P.A. Nikrityuk, K. Eckert, R. GrundmannInstitute for Aerospace Engineering,

Dresden University of Technology, Germany

2nd Sino-German Workshop on Electromagnetic Processing of Materials October 16-19, 2005, Dresden, Germany

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Historical preamble of a pulse electric discharging (PED) in metallurgy

• The goal of PED is the modification of the microstructure during solidification

• A. Mirsa (Metal. Trans. A, 1985, 1986) - Pioneering publication about en experimental study of DC passing though the solidified melt. Grain size refinement was reported.

• M. Nakada et al (ISIJ Int., 1990) - Detailed experimental study of the PED impact on Sn15wt%Pb alloy solidification. Hypothesis: the Lorentz force (Pinch force) is responsible for the grain refinement through mechanical shearing of dendrites.

• A. Prodhan et al (Met. Mat. Trans.B, 2001) – Experimental study of solidification of Aluminum in electric field. The reduction of pinhole porosity and columnar-to-equiaxed transition was reported by application DC and 50 Hz AC.

• M. Gao et al (Mat. Sci Eng. A, 2002) – Experimental study of the ZA27 alloy solidification treated with PED. Modification of the dendrite grain size from larges to the smaller was reported.

SFB609

Historical preamble of a pulse electric discharging (PED) in metallurgy

• The goal of PED is the modification of the microstructure during solidification

• A. Mirsa (Metal. Trans. A, 1985, 1986) - Pioneering publication about en experimental study of DC passing though the solidified melt. Grain size refinement was reported.

• M. Nakada et al (ISIJ Int., 1990) - Detailed experimental study of the PED impact on Sn15wt%Pb alloy solidification. Hypothesis: the Lorentz force (Pinch force) is responsible for the grain refinement through mechanical shearing of dendrites.

• A. Prodhan et al (Met. Mat. Trans.B, 2001) – Experimental study of solidification of Aluminum in electric field. The reduction of pinhole porosity and columnar-to-equiaxed transition was reported by application DC and 50 Hz AC.

• M. Gao et al (Mat. Sci Eng. A, 2002) – Experimental study of the ZA27 alloy solidification treated with PED. Modification of the dendrite grain size from larges to the smaller was reported.

SFB609

Historical preamble of a pulse electric discharging (PED) in metallurgy

• The goal of PED is the modification of the microstructure during solidification

• A. Mirsa (Metal. Trans. A, 1985, 1986) - Pioneering publication about en experimental study of DC passing though the solidified melt. Grain size refinement was reported.

• M. Nakada et al (ISIJ Int., 1990) - Detailed experimental study of the PED impact on Sn15wt%Pb alloy solidification. Hypothesis: the Lorentz force (Pinch force) is responsible for the grain refinement through mechanical shearing of dendrites.

• A. Prodhan et al (Met. Mat. Trans.B, 2001) – Experimental study of solidification of Aluminum in electric field. The reduction of pinhole porosity and columnar-to-equiaxed transition was reported by application DC and 50 Hz AC.

• M. Gao et al (Mat. Sci Eng. A, 2002) – Experimental study of the ZA27 alloy solidification treated with PED. Modification of the dendrite grain size from larges to the smaller was reported.

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Problem formulation

macroscaleelectric current density is

homogeneousmicroscale mesoscale

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R0=25 mm, H0=75 mm

sVj ||

Problem formulation

macroscaleelectric current density is

homogeneousmicroscale mesoscale

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R0=25 mm, H0=75 mmmicro- and mesoscale

electric current density is NOThomogeneous

ls

sVj ||

Macro-energy transport during Sn15wt%Pb solidification by DC

application

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2Et

HTTct p

Steady DC from 50 s to 80 s during UDS

Macro-energy transport during Sn15wt%Pb solidification by DC

application

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2Et

HTTct p

Periodic DC with period “on and off ” 1 sec V1.0

Steady DC from 50 s to 80 s during UDS

Joule heating is reduced !!!!!

DC is switch on after30 sec and switched off after 60 sec

0.1V, 4672 AVolume fraction of the liquid Temperature

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Joule heating effectSFB609

Joule heating in the liquid phase >> Joule heating in the solid phase

ls 5

Axial profiles of the temperature and the electric potential at t = 70 sec

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solid liquid

Axial profiles of the temperature and the electric potential at t = 70 sec

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Analytic model – Nikrityuk et al, 2005, Wiley-VCH Verlag

11

101

s

sls AA

AA

ss HHA /0lsA /

solid liquid

Mesoscale considerationSFB609

Rd=10-4 m

Vs=10-4 m/s

E=1-30 V/m

Electroconducting non-homogeneous media,Nikrityuk et al, Met. Mat. Trans, 2005, submitted

Spatial distribution of electric potential, current density and Joule heating

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electric potential current density

Joule heating

Spatial distribution of the velocity field SFB609

sVu

sVu

sVu

Spin-up of the interdendritic liquid

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d dH R

zrdd

rz drdzuurHR

U0 0

222

2

Nikrityuk et al, Phys Fluids, 2005

Time scale of spin-up is 10-3 sec !!!!

Conclusions

• Application of PED perpendicularly to the solidification front lead to a much stronger heating

of the liquid phase in comparison to the solid phase (the heating is caused by the Joule heating

effect)

• A shorter duration of PED decrease of the Joule heating of the melt

• The inhomogeneity of the electrical current in the mushy zone induces a Lorentz force (pinch

force), which induces a toroidal vortex near the dendrite tip. This convection may lead to the

accumulation of solute at the dendrite tip and obstruction of the columnar grain growth

(Martorano et al, 2003, Willers et al 2005, Eckert et al 2005)

• The spin-up time of the vortex has order of O(10-3) sec for Ez of order O(10) V/m

Models proposed to use• Macroscale level: a variant of the mixture model (Stefanescu, 1996)• Microscale level: Phase-field model (Karma 1996, Beckermann, 1999)

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Cited publications

• P.A. Nikrityuk, M. Ungarish, K. Eckert, R. Grundmann. “Spin-up of a liquid metal flow driven by a rotating magnetic field in a finite cylinder. A numerical and analytical study“ Phys. Fluids 17, 2005, 067101-1-016

• P.A. Nikrityuk, K. Eckert, R. Grundmann. “Numerical study of the influence of a rotating magnetic field on unidirectional solidification of a binary metal alloy”, I.J.Heat and Mass Transfer, in press, 2005

• P.A. Nikrityuk, K. Eckert, R. Grundmann. “Rotating magnetic field driven flows in conducting inhomogeneous media. Part I: Numerical Study“, submitted to Metallurgical and Materials Transactions B, 2005

• P. A. Nikrityuk, K. Eckert, R. Grundmann. Proceeding of Continuous Casting Conf., Wiley-VCH Verlag, pp. 1-14, 2005.

• S. Eckert, B. Willers, P. Nikrityuk, K. Eckert, U. Michel, G. Zouhar. Application of a rotating magnetic field during directional solidification of Pb-Sn alloys: Consequences on the CET. Mat. Sci. Eng. A, in press, 2005.

• Dr. YANG “Microstructure evolution of semi-solid magnesium alloy AZ91D under electric current”

• Dr. PAN “Impose of electric field on crystallization of metallic amorphous”

Proposed partners from China

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