NUMERICAL STUDY OF THE INFLUENCE OF AN APPLIED ELECTRICAL POTENTIAL ON THE SOLIDIIFCATION OF A BINARY METAL ALLOY

1
NUMERICAL STUDY OF THE INFLUENCE OF AN APPLIED
ELECTRICAL POTENTIAL ON THE SOLIDIIFCATION OF A
BINARY METAL ALLOY
SFB 609

• P.A. Nikrityuk, K. Eckert, R. Grundmann
• Institute for Aerospace Engineering,
• Dresden University of Technology, Germany

2nd Sino-German Workshop on Electromagnetic
Processing of Materials October 16-19, 2005,
Dresden, Germany
2
Historical preamble of a pulse electric
discharging (PED) in metallurgy
SFB 609

• 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 Sn15wtPb
  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.

3
Historical preamble of a pulse electric
discharging (PED) in metallurgy
SFB 609

• 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 Sn15wtPb
  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.

4
Historical preamble of a pulse electric
discharging (PED) in metallurgy
SFB 609

• 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 Sn15wtPb
  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.

5
Problem formulation
SFB 609
macroscale electric current density is
homogeneous
microscale
mesoscale
R025 mm, H075 mm
6
Problem formulation
SFB 609
macroscale electric current density is
homogeneous
microscale
mesoscale
micro- and mesoscale electric current density is
NOT homogeneous
R025 mm, H075 mm
7
Macro-energy transport during Sn15wtPb
solidification by DC application
SFB 609
Steady DC from 50 s to 80 s during UDS

8
Macro-energy transport during Sn15wtPb
solidification by DC application
SFB 609
Steady DC from 50 s to 80 s during UDS
Periodic DC with period on and off 1 sec

Joule heating is reduced !!!!!
9
DC is switch on after30 sec and switched off
after 60 sec
SFB 609
Volume fraction of the liquid
Temperature
0.1V, 4672 A
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Joule heating effect
SFB 609
Joule heating in the liquid phase gtgt Joule
heating in the solid phase
11
Axial profiles of the temperature and the
electric potential at t 70 sec
SFB 609
solid
liquid
12
Axial profiles of the temperature and the
electric potential at t 70 sec
SFB 609
solid
liquid
Analytic model Nikrityuk et al, 2005,
Wiley-VCH Verlag
13
Mesoscale consideration
SFB 609
Rd10-4 m Vs10-4 m/s E1-30 V/m
Electroconducting non-homogeneous
media, Nikrityuk et al, Met. Mat. Trans, 2005,
submitted
14
Spatial distribution of electric potential,
current density and Joule heating
SFB 609
electric potential
current density
Joule heating



15
Spatial distribution of the velocity field
SFB 609



16
Spin-up of the interdendritic liquid
SFB 609
Nikrityuk et al, Phys Fluids, 2005
Time scale of spin-up is 10-3 sec !!!!
17
Conclusions
SFB 609

• 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)

18
Cited publications
SFB 609

• 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.

Proposed partners from China

• Dr. YANG Microstructure evolution of semi-solid
  magnesium alloy AZ91D under electric current
• Dr. PAN Impose of electric field on
  crystallization of metallic amorphous