Magnet properties D. Chateigner CRISMAT-ENSICAEN, Caen, France M. - PowerPoint PPT Presentation

2 nd International Conference Texture and Anisotropy of Polycrystals, Metz, France, July 2004 Texture development in Nd-Fe-B and Nd-Fe-V alloys by hot forging in view of improving permanent Magnet properties D. Chateigner CRISMAT-ENSICAEN, Caen, France M. Morales SIFCOM-ENSICAEN, Caen, France S. Rivoirard, I.Popa, P. de Rango, D. Fruchart CRETA and Cristallographie-CNRS, Grenoble, France B. Ouladdiaf Institut Laue Langevin, Grenoble, France c

- Some intrinsic magnetic and extrinsic magnet properties - QTA and anisotropic magnetisation curves: ErMn 4 Fe 8 C case - Nd-Fe-B-Cu, Nd-Fe-V alloys - conclusions

2 nd International Conference Texture and Anisotropy of polycrystals, Metz, France, July 2004 Permanent magnet characteristics Intrinsic properties Hard magnetic phase - Saturation magnetisation, M s - Magnetocrystalline anisotropy - Curie temperature - Anisotropy field Extrinsic properties - Remanence, M r - Coercive field, H c - Maximum energy product, BH max Introduction

ErMn 4 Fe 8 C Structural determination: j i i 2a j 2a M. Morales et al.: J. Magn. i And Magn. Mat. 196 (1999) j j f f j 703 i i z=0 z=1/2 j j i i 2a z=1/4 et 3/4 i i j f f j j b i a j j i i 2a 2a Easy-plane tetragonal phase magnetic moments in the (a,b) planes

⊥ (a,b) H meas // z // (a,b) Same demagnetising factor S(Q) θ θ θ Sample A Sample B H text z N S S N H text S(Q) θ H text axial H text radial

160 A 160 220 + 211 140 Sample B B 140 Quantitative Texture Analysis 120 Intensity (a.u.) 100 220 + 211 80 120 002 60 400+321 411 202 420 40 301 100 20 Intensity (a.u.) RP 0 = 1.2 % 25 30 35 40 45 2 θ (°) 80 ---- // (a,b) F 2 = 1.3 mrd 2 002 60 ---- ⊥ “ S = -0.13 301 40 20 0 28 29 30 31 32 33 34 35 36 37 38 2 θ (°) max {001}: 3.9 mrd min: 0.5 mrd {001} radial distribution: ρ 0 (0.5 mrd) + PV (HWHM = 12°)

Anisotropic magnetisation curves 8 H A 7 Μ / / / 6 B / fu ) 5 aimantation ( µ 4 M random 3 2 Μ ErMn 4 Fe 8 C ⊥ 1 T= 300K 0 0 2 4 6 8 10 H (T)

Model for M ⊥ : M(H meas ) = M S cos( θ g - θ ) E(H meas ) = K 1 sin 2 θ −Η M S cos( θ g - θ ) ⊥ (a,b) H meas anisotropy Zeeman energy energy � c � 2 K sin θ cos θ M dE = θ g H 1 0 = meas M sin ( θ θ ) d − θ S g θ H A = 2K 1 /M S M S = 5.24 µ B /fu φ O H sin θ cos θ meas = x H sin ( θ - θ ) A g

π Normalised Probability 2 2 π function F, to find F( θ , φ ) sin θ d θ d φ 1 = ∫ ∫ g g g c-axes in d y : 0 0 θ = ϕ = g π 2 π ∫ 2 G( θ ) sin θ d θ 1 Fibre texture: = g g g 0 θ = g ( ) G ( ) 1 PV ( ) θ = − ρ θ g 0 g Finally: π 2 M ( ) 2 1 PV( θ ) sin θ cos( θ θ ) d θ M ⊥ = π ∫ − ρ − + ρ 0 g g g g 0 random M S 0

1.00 M ⊥ 0.95 0.90 0.85 0.80 0.10 0.75 M / M S S 0.70 ) / M 0.08 0.65 M // calculated 0.06 0.60 0.55 0.04 (M ? - M 0.50 0.02 0.45 0.40 0.00 0 1 2 3 0.35 H / H A 0.30 0.25 0 1 2 3 4 H / H A Morales, Chateigner, Fruchart: J. Magn. Mag. Mat. 2003

2 nd International Conference Texture and Anisotropy of polycrystals, Metz, France, July 2004 Nd 2 Fe 14 B Crystallographic structure Intrinsic magnetic properties: hard magnetic phase - Uniaxial anisotropy → c-axis = easy magnetisation P4 2 /mnm c axis - Ha= 7T - M s = 1.61 T - T c = 315°C a a Nd Fe B Introduction: intrinsic properties

2 nd International Conference Texture and Anisotropy of polycrystals, Metz, France, July 2004 NdFe 12-X V X N compounds Crystallographic structure Nitrogenation • space group I4/mmm N atoms in 2b sites Intrinsic magnetic properties: hard magnetic phase - c-axis = easy magnetisation axis - Ha= 1.5T → 11 T - M s = 1.13 T → 1.37 T - T c = 340°C → 510°C N Introduction: intrinsic properties

2 nd International Conference Texture and Anisotropy of polycrystals, Metz, France, July 2004 Permanent magnet extrinsic properties: anisotropy c ANISOTROPY c M // r c ⊥ M c r c common orientation of the easy magnetisation c axes of the crystallites c c Orientation of magnetic particles in a non magnetic matrix Introduction: extrinsic magnetic properties

2 nd International Conference Texture and Anisotropy of polycrystals, Metz, France, July 2004 Permanent magnet extrinsic properties: coercivity COERCIVITY H C Grain size control of the hard magnetic phase Intergranular phase distribution → Magnetic decoupling 10 µ m Secondary phases Introduction: extrinsic magnetic properties

2 nd International Conference Texture and Anisotropy of polycrystals, Metz, France, July 2004 Preparation route Nitrogenation Powdering (Nd-Fe-V) (HD Process) Induction Hot forging Melting Magnet Powder and Casting Anisotropy + Coercivity Bulk Magnet Experimental details

2 nd International Conference Texture and Anisotropy of polycrystals, Metz, France, July 2004 High-speed hot forging ε = 125 s -1 EXPERIMENTAL DEVICE Thermomechanical treatment of the as-cast alloy to induce permanent magnet properties Piston Hammer ouverture vitrée Window Working chamber de l ’ enceinte Airtight passage and sliding of the comme phase verte Argon inductive coil entrance Heating coil Sample Tachymeter Vacuum elements Experimental details

2 nd International Conference Texture and Anisotropy of polycrystals, Metz, France, July 2004 Microstructures forged sample as-cast alloy NdFe 14 B Black: iron 20 µ m 10 µ m 10 µ m White intergranular phase Grey: hard magnetic phase NdFe 10.5 V 1.5 5 µ m 10 µ m Results: microstructure

2 nd International Conference Texture and Anisotropy of polycrystals, Metz, France, July 2004 Permanent magnet properties Nd 15,5 Fe 78 B 5 Cu 1,5 alloys NdFe 10,5 V 1,5 N+10% Nd alloys 15 Parallel to the 1.4 10 Forging direction 1.2 5 1.0 perpendicular forging direction 0.8 M(T) 0 paralel to the to the forging 0.6 magnetic field direction -5 forging direction 0.4 perpendicular to the -10 0.2 magnetic field H (kOe) int -15 0 -80 -60 -40 -20 0 20 40 60 80 0 1 2 3 4 5 6 7 H(T) H c = 10 kOe (795 kA/m) Isotropic magnet B r = 10 kG (1 T) BH max = 24 MGOe (191 kJ/m 3 ) Results: permanent magnet properties

2 nd International Conference Texture and Anisotropy of polycrystals, Metz, France, July 2004 Texture development in the Nd 2 Fe 14 B phase ILL, D1B ⇒ Fibre texture of Nd 2 Fe 14 B ⇒ c-axes // forging direction Y 239 100 (1 mrd) forging direction Y 24 ¤ ¤ {001} {100} Cristallographic texture ⇒ extrinsic anisotropy Texture

2 nd International Conference Texture and Anisotropy of polycrystals, Metz, France, July 2004 Texture investigation of the NdFe 10,5 V 1,5 phase ILL, D20 texture with <100> axes // forging direction Y 2 components, ≈ fibre forging direction Y Z X Texture

2 nd International Conference Texture and Anisotropy of polycrystals, Metz, France, July 2004 Texture development of the NdFe 10,5 V 1,5 phase X [010] // Y c 1 [001] in (X,Z) plane ⊥ forging a 1 a 2 direction Y 60° 30° 30° Z Y 60° no extrinsic magnetic anisotropy c 2 can be observed on forged bulks Texture

2 nd International Conference Texture and Anisotropy of polycrystals, Metz, France, July 2004 Influence of primary iron on the NdFe 10,5 V 1,5 phase stabilisation and texturing 100 a 80 NdFeV alloys The image cannot be displayed. Your computer may not have enough memory to open Free iron centre (%) the image, or the image may have been corrupted. Restart your computer, and then Nd-rich phase+ (Fe,V) → NdFe 10,5 V 1,5 60 open the file again. If the red x still appears, you may have to delete the image and then insert it again. 1:12 phase centre (%) Free iron periphery (%) 40 1:12 phase periphery (%) 20 0 0 5 10 15 20 25 %Nd NdFe 10,5 V 1,5 phase stabilisation: optimised microstructure for Nd=10% Contribution of minor phases to the texturing process of the main phase

2 nd International Conference Texture and Anisotropy of polycrystals, Metz, France, July 2004 Influence of primary iron on the Nd 2 Fe 14 B phase texturing 18 18 BH max (10*kJ/m 3 ) 16 Free Iron (volume %) 16 14 14 12 12 10 10 8 8 6 6 4 4 Free iron (volume %) 2 2 0 0 10 12 14 16 18 20 22 10 12 14 16 18 20 22 y (Nd-at %) y (Nd- at %) NdFeBCu as cast alloys NdFeBCu forged alloys Optimised microstructure and magnetic properties for Nd=15,5% Contribution of minor phases to the texturing process of the main phase

2 nd International Conference Texture and Anisotropy of polycrystals, Metz, France, July 2004 Influence of the intergranular volume fraction on texturing NdFeBCu alloys NdFeV alloys 35 Intergranular phase (volume %) forged alloy: centre 16 as cast alloys 30 forged alloy: periphery forged alloys as cast alloy (theoretical) 25 12 20 8 15 10 4 5 0 0 10 12 14 16 18 20 22 0 5 10 15 20 25 y (% Nd) %Nd volume of intergranular phase = volume of liquid at T f NdFeBCu alloys NdFeV alloys volume fraction ↑ with %Nd %Nd>10%: liquid phase segregation Contribution of minor phases to the texturing process of the main phase

2 nd International Conference Texture and Anisotropy of polycrystals, Metz, France, July 2004 Effect of iron on the hot deformation process NdFe 10.5 V 1.5 + 10%Nd Nd 15,5 Fe 78 B 5 Cu 1,5 20 µ m 10 µ m Forging energy mainly used for the plastic deformation of iron Contribution of minor phases to the texturing process of the main phase