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THERMO -MAGNETIC HEAT TREATMENT FOR TEXTURING H. Garmestani, Professor of Materials Science and Engineering
5/17/2004
Funded by ARO
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Magnetic Annealing at NHMFL
5/17/2004
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Thermo-magnetic Heat Treatment Texturing and the control of grain size/grain boundary character. Application to Diamagnetic (Zink,…) Magnetic NdFeB, permanent magnets FePd Nd2Fe14B/a-Fe-type nanocomposites
soft magnets (Fe-Si) non-magnetic (Polymers, nano-tubes,.. For the alignment 5/17/2004
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Magnetic Sensors Based on GMR technology
Magnetic Force Microscope
Magnetic Sensor Chip 5/17/2004
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Micro-actuator Devices
Gripper, compliant systems
5/17/2004
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Control of Crystal Orientation 1- Heat treatment 2- Deformation 3-??
e3 a3
a3
a2 e2 e2
a1
a1
OIM Scan data
e1
Orientation g 5/17/2004
a2
Orientation g’ 6
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The Stereographic Projection • Using the inclination of the normal to the crystallographic plane
5/17/2004
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{hkl} Cube Texture {001} ND
TD
RD
ND
{100}
{001} {010}
RD
TD
{001} texture
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Texture • • •
Crystal grains can orient themselves preferentially giving rise to TEXTURE Some preferred orientations are important for certain properties It happens that the increase of Goss orientation grains improves magnetic properties
{011} Goss texture ND
RD
(110)
TD [100]
TD
5/17/2004
(110)
RD
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Texture Measurement Þ X-Ray diffraction
X-Ray goniometer with texture attachment 5/17/2004
Schematic representation of Pole figure measurement 10
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Harmonic Method •
The total intensity of diffracted X-rays at any point (a, b) on the (hkl) pole figure is:
1 P( hkl ) (a , b ) = 2p •
ò
2p
0
f (Y , Q, f )dG
Expansion of above equation in a series of spherical harmonic functions yields ¥
l
P( hkl ) (a , b ) = å å Qlm Pl m (cos a )eimb l =0 m = - l
•
The relationship between the orientation distribution coefficient and the pole figure coefficient l
Qlm =
n -inh W P (cos x ) e å lmn l
n=-l 5/17/2004
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Experimental setup Rod High T furnace Resistive magnet, 195 mm bore, 20 Tesla Hot zone, 1200 °C
5/17/2004
sample holder
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High Temperature Furnace Insert Three different types of furnaces have been designed for experiments in flowing gas and in vacuum: 1) Up to 700o C for 30 or 33Tesla magnet 2) Up to 1250o C for 20 Tesla magnet 3) Up to 1600o C for 20 Tesla magnet 5/17/2004
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Texture Development in Zn-1.1%Al Alloy Strong Magnetic Field Background Bismuth polycrystal; Mullins, 1956
Bismuth bicrystal; Molodov, Gottstein, Heringhaus & Shvindlerman, 1997
5/17/2004
Zinc bicrystal with twin boundary; Konijnenberg, Molodov, Gottstein & Shvindlerman., 2000
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Some observations on the effect of magnetic annealing •
Turner, 1949 – FeCo • Strong enhancement of the (100)[110] recrystallized texture
•
Mullins, 1956 – ( Bismuth, 5T and 8T, 250C) • Magnetic anneal. Has a great effect on grain boundary motion
•
Watanabe, 1990 – (FeCo, 0.2T and 0.5T, below Tc) • Magnetic Anneal. retarded recristallization, big effectin the type and distribution of GB (GBCD)
•
Masahashi, 1998 – (FeSi, 10T, below Tc) • No diference in grain size and higher percentage of low-angle GB for the magnetic annealed sample
•
Matsuzaki, 1999 – (Carbony Iron sintering, 1.5T, below Tc) • Application of magn.field enhance densification and grain growth of pure iron compact. • More homogeneous microstructure • Magnetization and susceptibility improvement
•
Bacaltchuk, 2000 – (FeSi, 8T, below and above Tc, Secondary recrystal.) • – no effect on grain size, improvement of Goss texture.
5/17/2004
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Texture Development in Zn-1.1%Al Alloy under Strong Magnetic Field Bicrystal of Zn with symmetric tilt 90° < 10 1 0 > boundary H Grain A
45 °
Grain A
á10 1 0 ñ á11 2 0 ñ 90 °
GRAIN BOUNDARY BASAL PLANES
Grain B
a
( 0001 )
Grain B
b
Geometry of bicrystals (a) and their orientation to the field during annealing (b). 5/17/2004
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Texture Development in Zn-1.1%Al Alloy under Strong Magnetic Field Bicrystal of Zn with symmetric tilt 90° < 10 1 0 > boundary
Annealing with and without field B=17 T; T=663K; 5 min
H
Grain A
B= 0 T; T=663K; 100 hours
[0001] Original boundary position
Final boundary position
Grain A
Direction of boundary migration
[0001] Original boundary position
Final boundary position
0.5 mm
Grain B
Grain B
0.5 mm
View on the lateral surface of the sample. Initial boundary shape changes under the 5/17/2004 magnetic driving force and force provided by the boundary surface tension.
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Texture Development in Zn-1.1%Al Alloy under Strong Magnetic Field Texture and microstructure of Zn-1.1%Al after rolling with 99% reduction RD
A
IA
B
IB
RD
RD
30.3
32.9
5.0 TD
5.0
a
5.5
21.8 b
c
RD
RD
43. 7.4 6 41.2 44.3
7.7 59.9
d
TD
21.9
TD
77.0 e
Pole figures of Zn-1.1%Al sheet specimens after annealing. (a) without field; (b) oriented parallel to the field; (c) tilted at +19° to the field about the TD, (d) tilted at -19° to the field about the TD.
5/17/2004
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RECRYSTALLIZATION OF STEEL (Electrical Steel Alloys) • Electrical Steels or Silicon Steels are of prime importance in the electrical industry, which consumes hundreds of thousands of tons every year. • Two types of silicon steels are of interest: – GO (grain oriented) silicon steel, used in power transformers and electrical energy distribution transformers, and
– GNO (non-oriented grain) silicon steel, used in hydroelectric power plant generators, electric motors, ballasts for fluorescent lamps and hermetic motors for refrigerators, freezers and air conditioning. 5/17/2004
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Magnetic Properties •
•
•
•
Soft magnetic material – Silicon steel Ä Easily magnetized and demagnetized High saturation magnetization – permiting the material to do the most work High permeability – permits high saturation magnetization to be obtained with small imposed fields Small coercivity – indicating that the domains can be reoriented with small fields
5/17/2004
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Effect of Texture Ø
Ø
The easiest direction of magnetization, , // RD and an intermediate direction of magnetization, [110] // ND. The fiber type of texture is detrimental to the magnetic properties [111] direction is the hardest magnetization direction. ND
5/17/2004
Magnetization Curve of iron
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Experimental Procedure Silicon steel (0.28% Si) As received FeSi Primary annealed at 815C 10% temper cold rolled
Magnetic Annealing 8 Tesla - 1 hour at 737, 787 and 837C Inert atmosphere
Metallography 5/17/2004
Ordinary Annealing 1 hour at 737, 787 and 837C Inert atmosphere
X-Ray
measurents 22
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111 fiber (Gamma)
Goss Texture Intensity
{111}6
Goss Component 7 6 Intensity
5
{111}
