Nghiên cứu chế tạo nam châm đất hiếm NdFeB sử dụng bột vật liệu chế tạo bằng phương pháp hấp thụ hydro

DAI HOC QUOC
GIA
HA
NOI
TRl/CfNG
DAI HOC KHOA HOC
Tl/NHIEN
NGHIEN
CtJtJ
CHE TAO NAM CHAM DAT
HIEM
NdFeB
Sir
DUNG
BOT
VAT
LIEU
CHE
TAO BANG
PHUONG
PHAP HAP THU HYDRO
MA SO:
QT-06-15
CHU TRIDE
TAX:
PCS. TS.
LUtJ TUAN TAI
CAC CAN Bp TRAM GIA : TS.
LlTU HOAI
NAM
ThS.

NCS. TA VAN KHOA
ThS.
PHAM
THI THUONG
Ha
Noi
- 2006
BAO CAO TOM TAT
1-
Ten de tai:
Nghien
cihi
che tao nam cham dat hiem NdFeB
su
dung hot vat lieu
che
tao
b^ng
phiiang
phap hap thu hydro
2-
Ma
so: QT-06-15
3-
Thol
gian
thiic
hien : 12 thang
(tir
03/2006 tdi 03/2007 )

4-
Chu
tri
de tai: PGS. TS.
Lim
Tua'n Tai
Phong
thi
nghiem vat
ly
nhiet do thap, trudng DHKH Tu nhien ,
Dai hoc qudc gia Ha Noi
5- Can bo tham gia de tai:
PGS.
TS. Luu
Tua'n
Tai
ThS.NCS. Ta Van Khoa
ThS.Pham thi
Thuong
TS.
Luu hoai Nam
Va cac cong tac vien khac
6- Muc tieu va noi dung nghien curu:
- Che tao he
ha'p
thu hydro don gian de ap dung cdng nghe HDDR
- Nghien
ciiu ,tim
ra cdng nghe HDDR thfch hop.

- Che tao cac nam cham ket dmh NdFeB tren
co
sd bdt vat lieu che tao bang
phuong
phap hap thu hydro (ap dung cdng nghe HDDR) dat tich nang
lugng cue
dai
Idn hon
5 MGOe
7-
Cac ket qua dat
dugc:
Sau mot thdi gian thuc hien de
tai,
chiing
tdi da thu dugc mot sd ket qua
nhu
sau:
- Da
xay
dung va van hanh tot he thiet hi hap thu
khi
hydro trong nhiet do cao (he
thiei bi HDDR).
- Su dung he thiei bi HDDR
xay
dung dugc de khao sat cac hgp kim va cac dieu
kien cdng nghe trong quy trinh HDDR va da che tao thanh cdng ca hai
loai
hot

HDDR khdng di hudng va di
hudng.
- Mot quy
trinh
nhiet vdi nhiet do cao
han
va thdi gian dai hon da dugc
lira
chon
thich
hgp cho cac vat lieu cd pha tap mot lugng nhd Zr
(0.1%
Zr).
Ket qua la da
che'
tao dugc nam cham ket dmh tren ca sd bdt hgp kim
NdigFeys.gZroiBs
di hudng che tao bang phuong phap HDDR dat
tich
nang lugng
cue
dai
(BH)^,,
= 9.95 MGOe.
8-
Tinh
hinh kinh phi cua de
tai:
*T6ng
kinh phi dugc cap: 15 trieu dong Viet nam

Da quyei toan vdi tai vu xong
KHOA
QUAN Lt
(K^
va ghi
TO
ho ten)
u
s'
CHU TRI DE TAI
(Ky va ghi ro ho ten)
PGS.
TS. Luu Tuan Tai
CO QUAN CHU TRI DE TAI
PHOHlioTRUOMO
PGS
TS.t&-^^^**»
SUMMARY REPORT
I. Project Title:
To investigate and fabricate the NdFeB bonded magnets use HDDR powder
II.
Project Director: Ass.Prof.Dr. Luu Tuan Tai
Cryogenic
laboratory,Faculty
of Physics
College of Natural Science, Hanoi National University
IILGrant
number : QT -
06-15
IV. Key Project

Staff:
Dr. Luu hoai Nam
MA. Phs. Ta Van Khoa
MA. Phs. Pham thi Thuong
And some others
V. Aims and contents of the project:
- To investigate the influence of temperature and time of HDDR technology
condiSon
o^
the hard magnetic properties of the NdFeB bonded magnets m order to
find the good condition to produce NdFeB bonded magnets.
To investigate and fabricate the NdFeB bonded magnets use HDDR powder
VI.
Summary of Achievements of project:
- To set up the HDDR equipment
- To investigate the influence of temperature and
time
of HDDR technology
condition and addition effect of small amount of Zr
on
the hard magnetic
properties of the NdFeB bonded magnets
in
order to
find
the good condition to
produce NdFeB bonded magnets.
^ e
tu^
-

Isotropy and anisotropy NdFeB HDDR powders were produced for the
oroduction
bonded magnets
HDDR process with higher temperature and longer heat treatment t.me
wa
selected
to suit for the materials with a small amount of addition of Zr, to result
in produced the bonded magnets with
(BH)n,ax=
9.95 MGOe
Muc
luc
I-
GI6ITHIEU Trang?
II-
MVC TIEU NGHIEN
CIRJ CHINH
CUA DE
TAI
16
W
Ji.
Ill-
CAC KET
QUA KHOA HOC CUA
DE TAI 17
3.1 He mau hop kim
NdigFcyg.xBg
18
3.2

He mau hgp kim Nd,6Fe76.xZrxB8vaix =
0.1,0.2,0.3
va
0.5 22
IV.KETLUAN
28
V. TAI LIEU THAM KHAO
29
NOI DUNG BAO CAO
TONG
KET
I.
MCf
DAU
Viec che tao cac NCVC dua tren ca so cac hgp kim chua dat hiem
vao nhiing nam 70 da ma
dku
cho mot cuoc
each
mang mai trong
ITnh
vuc
dien va dien tu. Dac biet la loai nam cham
SmCos
va (SmPr)Co5 c6 ten tren
>
y
f
thi trudng la Recoma vdi day du cac dac tinh can thiet cua NCVC va nang
lugng tu dat dugc la

(BH)n,ax
^ 22 MGOe
(175
KJ/m^).
Tuy nhien,
diSu
dang
tiec la Coban cd
triJ
lugng it va la mot kim loai dat tien. Vi the de cd
Igi
ve
mat kinh te, ngudi ta da
ti^n
hanh thay the mot phan nhd Co bang cac kim
loai nhu: Fe, Co, Mn, Al, Zr loai nam cham nay, Sm(Co, Cu, Fe,
Zr)8.5,
win
dat dugc nang lugng tu
r4t
cao la
(BH)max
^
33MGOe.
Song song vdi
each
giai
quyk
nhu tren, thi viec tim kiem cac vat lieu mdi lam NCVC chua
it hoac khdng chua Coban da trd thanh muc tieu cua nhieu cdng trinh nghien

cuu tren the gidi. Cudi nam 1983, Sagawa va cac cdng su da thanh cdng
trong viec
chl
tao mot loai NCVC mdi tren co sd cua hgp kim Nd-Fe-B
bang
phuong phap bdt thieu ket vdi nang lugng tu cue dai dat
(BH)max
= 36
MGOe,
lire
khang tu theo cam ung tu
BHC
^
11
KOe,
lire
khang tu theo tu
do
MHC
=
12 KOe,
B,
=
12.3 KG (1.23 Tesla). Pha hgp kim chinh cua loai
7
vat lieu nay la hgp kim
Nd2Fei4B.
Vat lieu nay d nhiet do phdng cd mdmen
tu bao hda cao
Ms =

120
Am^/kg.
'
y
1
If
Do nam cham ket dinh cd nhieu uu diem nhu: cd the che tao dugc cac
hinh dang rat
phue
tap vdi do chinh xac ve kich thudc tdi 0.01mm va cd the
dieu chinh gia tri
(BH)max
theo gia tri mong mudn trong mot khoang tuong
f
,
,
ddi
rdng(l-lOMGOe)
nen trong nhung nam gan day nam cham ket dinh da
phat trien rat manh va rdng rai. Cac hgp kim dung de che tao nam cham ket
dinh dugc che tao chu yeu bang phuong phap ngudi nhanh bang trdng ddng
quay va sau dd xu ly nhiet, cd kich thudc hat vao khoang 30 - 40 nm (kich
thudc nay nhd hon kich thudc cua don ddmen), ban than cac bdt
loai
nay da
cd luc khang tu rat cao khac ban vdi cac bdt NdFeB dugc tao ra bang
phuong phap nghien hgp kim khdi NdFeB. Mac du kich thudc cua hat
nSm
trong mdt khoang rdng nhung
tich

nang lugng tinh cho cac loai bdt nay vao
khoang 12 MGOe va trong dang nam cham ket dinh tich nang lugng
cue
dai
dat dugc chi vao khoang 10 MGOe. Cac dang nam cham
kk
dinh tao ra tu
bdt nam cham ngudi nhanh cd rat nhieu va tinh chat tu
cflng
nhu nang lugng
tu cua chung cung trai ra trong mot khoang nao dd, tuy nhien cd
th§
tdng
k^t
chung d ba loai khac nhau sau: cac nam cham
k§t
dinh tao ra
bSng
phuong
phap ep khudn, cac nam cham ket dinh tao ra bang phuong phap ep dun va
cac nam cham deo.
Cac bdt nam cham NdFeB che tao bang phuong phap ngudi nhanh
f
y
dung trdng ddng quay ma ta thuong goi la
MQI
d tren, sau khi ep ndng ta se
thu dugc mot loai san pham quen goi la
MQII,
sau dd ap dung cdng nghe ep

ndng khdng cd khudn ta thu dugc loai san pham
MQIIL
Cac nam cham cd
tich nang lugng dat tdi 45 MGOe va la cac nam cham di hudng, cd
th§
nghien thanh bdt ma van cdn
giir
dugc tinh di hudng
ciia
chung va sau dd cd
the dung de che tao cac nam cham ket dinh loai
dj
hudng. Kha nang tich
nang lugng cue dai
ciia
nam cham ket dinh che tao
tir
bdt
MQIII
cd the dat
tdi
19
MGOe. Tuy nhien quy
tri^h
cdng nghe la rat phuc tap va khd khdng
f
y
f f
t
f

che do ddng nhat chat lugng san pham; mac du loai vat lieu nay da xuat hien
va chiem mot ty
le
nhd trong cac san pham nam cham ket dinh ndi chung.
Mot trong nhung nguyen nhan lam cho
ITnh
vuc nam cham ket dinh
phat trien manh me la do
sir
phat trien
ciia
cac loai bdt nam cham nhu: bdt
nam cham
Sm2Fei7Nx,
cac
bdt^nam
cham NdFeB che tao bang quy trinh
cdng nghe HDDR, cac bdt nam cham dang hudng loai
HIREM,
cac bdt nam
f
y
f
cham che tao bang phuong phap bien dang ndng
Phu-cng
phap tach va tai hgp trong hydro HDDR (Hydrogenation
Dispropotionation Desorption and Recombination)
Hieu ung tach pha trong khi hydro da dugc khao sat ti mi vdi
nhiJng
dieu kien cu the khac nhau nhu trong dieu kien ap suat khi hydro la 30 bar

tai nhiet do
300°C
[R. Harris va cac cdng
sir,
1985] hay ap
suSt
la 1 bar tai
nhiet do
720°C
[Cadogan va Coey,
1986].
Hieu ung tach pha
(Disproportionation) cua NdFeB trong mdi trudng khi hydro la
sir
phan ra
(Decomposition) hgp thanh 3 pha thanh phan:
a-Fe,
Fe2B,
va
NdH2.
f f
\ \
r
,
Nam
1989,
tai hoi nghj qudc te
Ian
thu 10 ve nam cham dat hiem va
cac ung dung cua chung, Kyoto, Nhat ban, hai tac gia Takeshita va

Nagayama md ta qua trinh su dung xu ly nhiet trong hydro de che tao bdt
nam cham NdFeB vdi tich nang lugng
cue
dai cua vat lieu bdt la 95
KJ/m^
f f
If
(12 MGOe). Ho da dung bdt nay trdn vdi chat ket dinh de che tao nam cham
ket dinh NdFeB cd tich nang lugng la 8 MGOe va luc khang tu la
iHc
= 10
KOe.
Sir
phat trien mdi nay cd the canh tranh
true
tiep vdi ban quyen ve
nam cham
lanh
nhanh de san xuat cac nam cham ket dinh. Cflng can phai
luu y rang, cac bdt NdFeB tao ra
true
tiep tu hgp kim khdi NdFeB bang
phuong phap nghien thdng thuong hoac bang phuong phap tach vo trong
t •% f f
hydro (HD) cd the dung de che tao cac nam cham thieu ket nhung khdng du
y
f f f
do
Idn
ve

lire
khang tir de tao dugc cac nam cham ket dinh. Su mat mat luc
khang tir do qua trinh nghien hoac tach vd la do su sai hdng, gd ghe cua be
mat cac hat (do nghien da tao thanh cac tam mam dao tir va cac ddmen
nguge
khu tir).
Qua trinh xu
ly
nhiet trong mdi trudng khi hydro dugc md ta theo cac
budc nhu sau: vat lieu khdi NdFeB dugc dua vao dng
Id
rdi hut chan khdng
tdi
ap suat 10' Torr d nhiet do phdng, sau dd thdi khi hydro vao dng
Id
tdi
ap suat 1 bar, rdi thuc hien quy trinh
xir
ly nhiet tir nhiet do phdng tdi
khoang 750 -
900°C.
Sau dd dng
Id
dugc hut chan khdng va tat
Id
de vat lieu
nguoi
theo
Id.
Ket

thiic
qua trinh nay, vat lieu dugc kiem tra bang kinh hien
VI
truyen qua TEM, cho thay vat lieu bao gdm cac hat tinh the rat nhd chi cd
0.3fim
cua hgp kim NdFeB, kich thudc nay cd the so sanh dugc vdi kich
thudc
ciia
don ddmen
ciia
pha sat tir NdFeB va giai thich dugc tai sao luc
khang tir
iHc
cdn
giu*
nguyen dugc do
Idn
trong cac hat.
Trong thdi gian dau nhiing nam
1990,
McGuiness
ciing
cac cdng
sir
da giai thich qua trinh hinh thanh cac hat rat min cd
c§u true
tinh
thi
NdFeB
trong hai cdng

trinh
va da dat ten cho qua trinh xu ly nhiet trong hydro la
qua trinh HDD (Hydrogenation Disproportionation Desorption) va sau dd
dat ten
lai
cho qua trinh nay la HDDR (Hydrogenation Disproportionation
Desorption and Recombination). Qua trinh
FDDDR
la qua trinh md rdng
ciia
qua trinh HD bang each nung ndng vat lieu tach vd hydro gay ra
sir
tach pha
10
Nd2Fei4B
thanh cac pha thanh phan
NdH2,
Fe tu do,
Fe2B
(da dugc chi rd
bang
ket qua phan tich nhieu xa tia X) va pha
Nd2Fei4B
van cdn nguyen
khdng phan ra. Khi hut chan khdng, hydro dugc tach ra va cac pha thanh
phan tai hgp lai nhung d muc do nguyen tu do vay cac hat tinh the NdFeB
tao thanh cd kich thudc rat nhd, chi cd
0.3fim.
Hinh \.
Sado

dai
cuang ciia
quy trinh HDDR
Quy trinh HDDR tdng quat dugc dua ra trong hinh 1, nd chi
h\hu
dd
f "*,
dai cuong
ciia
cau true vi md sau mdi cdng doan cua quy trinh HDDR.
11
6
qua trinh
dhu
(hydrogenation) hydro tham nhap vao
viing
bien hat
(noi cd thanh
ph4n
pha giau Nd) cua
Nd2Fei4B
tao ra
NdH2.7.
Do cd su khac
nhau ve thdng sd mang
giiia
kim loai, hgp kim va hydrid cua chung, nen khi
cac nguyen tir hydro tham nhap vao cau true da lam gian mang
khien^mau
bi

t
= 0
phiit)
~a
CL
1.05
1.00
0.95
0.90
0.85
0.80
0.75
0.70
•
•
«
•
•
Ap
•
P=
•
P=
T
'•••.•.
suat hydro
=0.7bar
=0.2bar
=
750°C

••••• •• •
•«•
»
•
•
•
-50 0 200
250
50 100 150
thdi gian (phut)
Hinh 2,
Duang
cong ddng nhiet cua dien
traphu
thudc vao thai gian
cua quy trinh HDDR
tach vd thanh cac thanh phan be nhd.
Trong giai doan thu hai (Disproportionation), nguyen tu hydro tiep tuc
hap thu vao pha
NdaFe^B
trong cac hat lam cho cac hat nay phan ra thanh:
neodym hydrid, Fe va
Fe2B.
Do dd giai doan phan ra nay cd the dugc md ta
dudi dang phan ung nhu sau:
6
750°C:
NdzFeuB
+
(2±x)H2 02NdH2±x +12Fe

+
FczB
Trong dd gia tri x phu thudc vao ap suat cua khi hydro, d hinh 1 thi x
=
0.2.
Tiep theo hai qua trinh tren la qua trinh Desorption, nguyen tir hydro
sau khi tham nhap va lam phan ra mau thi dugc hut ra khdi mau,
NdH2±x
mat
hydro tao thanh Nd. 0 nhiet do cao, cac chat cdn lai sau khi tach hydro lai
12
kk
hgrp vai nhau tao thanh
hgp
chat NdFeB (co thanh
ph4n
hoa hoc nhu ban
dau) dudi dang tinh the nhd min hon so vdi ban dau, day chinh la qua trinh
tai hgp (Recombination).
6
day hai qua trinh Desorption va Recombination
xay ra mot each ddng thdi, Neodymhydrid tach hydro, Nd phan ung vdi
Fe2B
va Fe tao thanh hgp
chk
NdFeB.
Qua trinh HDDR dugc mieu ta dai cuong d tren, thuc ra la qua trinh
cdng nghe phuc tap phu thudc vao nhieu yeu td. Mot
trong.nhimg ylu
td anh

hudng tdi qua trinh
HDDDR
dd la ap
suk
khi hydro trong budng phan img,
Oliver Gutfleisch
ciing
cdng su da nghien cuu anh hudng nay thdng qua su
thay ddi dien trd mau trong qua trinh HDDR tai cac gia tri khac nhau
ciia
ap
suat khi hydro.
Sir
giam dien trd
chii ylu
la do su hinh thanh Fe, Neodymhydrid. Gia
tri dien trd dat trang thai can
bSng
sau qua trinh phan ra phu thudc vao ap
f ^
suat khi hydro
ciia
he. Tai ap suat cao hon, qua trinh phan ra xay ra nhanh
Id
han
Q,
00
jz
CL
o

le
c
P
0.40
0.35
0.30
0.25
0.20
0.15
0.10
0.05
0.00
#•
•
Ap suat hydro
• p =
1.0bar
• p = 0.7bar
A
p = 0.35bar
D
p = 0.2bar
T=750°C
% ^
^.
A A
16
20 0 4 8 12
Thoi
gian (phut)

Hinh 3. Do thi bieu thi phan
ung
phan
ra
phu thuoc vao thai gian.
f
>
hon, khien cho trang thai can bang dien tra dat dugc nhanh hon, nhu
duong
f
cong cham
tron
tren hinh 2 (tuong ung vai P = 0.7 bar) so vai duong cong
13
ch4m
sao (tuong ung vdi P = 0.2 bar). Gia tri dien trd tang khi Nd phan ung
ket hgp vdi Fe va
Fe2B
tao thanh
Nd2Fei4B.
Tir hinh 2 ta
thSy,
toe do phan
ung nay khdng phu thudc vao ap suat hydro ban dau.
m
Hinh 3 cho biet ty le
ciia
phan ung phan ra phu thudc vao
thoi gian
o

750°C
ddi vdi ap suat khi hydro khac nhau. Dd thi nay cho
hik sir
phu thudc
rat
Idn
ve mat ddng
lire
hoc
ciia
co
ch§
HDDR vao ap suat khi hydro. Vi du
ta thay rang, d
nhiing phiit
dau tien, tdc do phan ra trong ap suat la P
== lat
Idn
hon mot bac so vdi tdc do phan ra trong ap suat 0.2 at. Ket qua nay
chung td mot dieu la cd the dung ap suat hydro vdi tu
each
la mot anh hudng
r
t
If
"nhay
cam"
ciia
thiet bi kiem tra de tdi uu hda quy trinh HDDR.
Qua trinh HDDR da dugc ung dung trong viec che tao cac bdt NdFeB

bang
phuong phap nguyen tu hda trong khi tro tai hang Rhone Poulenc d
New Jersey, USA. Nguyen tu hda trong khi tro la mdt phuong phap don
gian, cung dugc su dung de che tao cac bdt kim loai, hgp kim khac (vi du
•J ^
nhu cac thep, nhdm ) da dugc su dung de tao ra cac hat NdFeB dang cau
cd dudng kinh nhd hon
200|am.
Hgp kim NdFeB dugc nau chay rdi dap nhd
dua vao mot cai
dTa
cd mot vdi phun vdi dudng kinh vai milimet dat tai day
dTa quay. Vat lieu dugc nau chay va phun ra do ap suat nen cao bang khi Ar
dl
nhan dugc cac giot hgp kim sau khi hda ran roi xudng day cua thiet
bj
la
noi tap hgp de thu lai cac hat vat lieu. Cac hat vat lieu tao ra bang phuong
\
f
phap nay cd luc khang tir
[He -
287.7 KA/m
{-
3 KOe) va sau khi ddng nhat
tai
500°C
-
900°C
trong mot gid thi

iHc
se tang
len
636 KA/m (8 KOe).
Tilp
theo cac hat NdFeB dugc dua vao quy trinh xu ly nhiet trong khi hydro (qua
trinh HDDR) vdi nhiet do xu ly la
850°C
thi luc khang tir tang len dat tdi gia
tri 795.7 KA/m
(-
10 KOe) do luc nay cac hat da cd kich thudc khoang
0.1
|im,
cd the so sanh vdi kich thudc cua don ddmen
ciia
pha sat tir NdFeB.
14
Mot kho khan la bgt NdFeB thu dugc sau qua trinh HDDR chi la bot
dang
huong.
Neu su dung bgt nay
dk
che tao nam cham kk dinh chi
-dat
dugc
(BH)n,ax =
40
KJ/m^
(5 MGOe). Neu

chi
tao nam cham thieu kk tu bot
nay thi hau nhu khdng trd thanh nam cham do
sir Idn
len rat nhanh
ciia
cac
hat sieu nhd.
DI
nang cao chat lugng bdt vat lieu,
chn
phai lam
th^
nao
dk
bdt tao ra bang phuong phap nay trd thanh bdt di hudng.
Tai hoi nghi quoc te
\kn thii 11
(nam 1990), Takeshita va Nagayama
f
^
cdng bd hg da tao dugc bdt di hudng
ciia
hgp kim
Ndi2.6Fe7oCon 4B6
bang
hieu ung pha tap. Ho da thu nghiem tren mot
loat
cac nguyen td pha tap la:
Al,

Ga, In, Si, Ge, Sn, Ti, Zr, Hf, V, Nb, Ta, Cu, Zn, Sb, Bi va tim thay hieu
f f r
ung mong mudn ddi vdi cac nguyen td: 0.1% nguyen tir Zr, 0.1% nguyen tir
Hf va cd 2% nguyen tu Ga. Vdi bdt tao ra tir hgp kim NdFeB pha tap 0.1%
Zr, ho da che tao dugc nam cham ket dinh di hudng vdi
Br
= 8.4 KG,
iHc =
9K0e va tich nang lugng
cue
dai
(BH)niax = 18
MGOe, tuy nhien tai thdi
diem nay hg khdng giai thich gi ve hieu ung pha tap.
O hoi nghi qudc te tai St. Louis nam 1992, tac gia McGuiness va cac
cdng su da bao cao viec che tao bdt vat lieu di hudng bang phuong phap
HDDR tir hgp kim
NdieFej^-xBgZrx
(x
==
0.1, 0.2, 0.3). Ho thay rang cac tinh
f
f r
•\
chat tir noi tai cua vat lieu rat nhay vdi nguyen td pha tap vao va cac dieu
f f
1
f f
kien
ciia

qua trinh HDDR. Vat lieu tdt nhat de che tao nam cham ket dinh di
hudng chua 0.1% Zr vdi
lire
khang tir noi tai
iHc ^
700 KA/m
(-
9 KOe) va
(BH)max =
150
KJ/m^
( 13
MGOe). Ho gia
thiSt
r^ng
di hudng cua bdt vat
lieu la do ddng gdp uu tien dinh hudng cua cac hat NdFeB sau qua trinh tai
hgp cd kich thudc cd nhd hon micromet va
mire
do di hudng cua nam cham
f f
^
ket dinh phu thudc vao cau
triic
cua hgp kim due ban dau, phu thudc vao
kich thudc cua cac hat bdt, tir dd cac hat bdt tai hgp hinh nhu se
djnh
hudng
trong
viing

dinh hudng ban dau
ciia
cac hat tinh the trong khdi hgp kim.
15
Peixin va cac cong
sir (1992)
da
chi
tao dugc cac nam cham kk dinh
tu>ot
HDDR cua hgp kim
(PrNd),2.5Fe69Co,,.5Ga,B6
vai cac thong so
B,
=
1.1
Tesla,
iHc
= 690 KA/m
(~
8.6 KOe). Ying va cac cong
sir
da che tao
nam cham tu bgt HDDR cua hgp phan:
Ndi3Fe74.4Co5.5B7Zro.i
co cac thong
s6
nhu sau:
B^
= 0.74 Tesla,

[He
= 744 KA/m (9.3 KOe) va tich nang lugng
cue
dai
(BH)^ax
= 98
Kj/m^
(~
12MG0e).
Phuong phap HDDR con dugc dung de
chi
tao cac nam cham
due
NdFeB vai gia tri
luc
khang tu cao.
Zhang cung cac cong
sir
(1991) da ap dung quy trinh HDDR trong
dieu kien khdng xay ra qua trinh tach vd (HD) cho cac mang mdng cua hgp
kim
Nd2.iFei4B
cd do day cd
4-^5mm.
Hieu ung tach vd khdng xay ra khi
>
t
f
hgp phan xung quanh hgp thuc 2:14:1 tai nhiet do phdng, tuy nhien de chac
f f

\
chan, do
Idn
cua mat cat vat lieu can phai nhd nhu vay va qua trinh tang
nhiet phai nhanh cd
40''C/1
phiit tir nhiet do phdng len nhiet do tach pha tir
770°C
-^830°C.
Day la khoang nhiet do tdi uu vi ngay dudi khoang nhiet do
nay, cac tinh the sat tu do dang cay van cdn tdn tai d gan hgp thuc do phan
ung Peritectic khdng hoan toan, cdn tren khoang nhiet do dd se xuat hien cac
\
f f
hat cd be mat rat
Idn,
lam giam tinh tir cung rat nhanh.
Trong de tai nay chiing tdi da chon nguyen td pha tap la Zr, va da dat dugc
nhimg ket qua rat kha quan.
IL
MUC TIEU CUA DE TAI
-Nghien cim anh hudng cua nhiet do, thdi gian va nguyen td pha tap Zr
trong cdng nghe HDDR
f
-Tim dugc qui trinh nhiet va thdi gian thich hgp che tao dugc bdt HDDR
dang hudng va dj hudng
f f
-Che tao dugc nam cham ket dinh NdFeB tir bdt HDDR cd tich nang
lugng
cue

dai
Idn
hon 5MG0e
16
III.CAC KET QUA
C
HINH CUA DE TAI
Nhu da ndi trong
pfian
trudc,
viec nghien ciru chi tiet cac qua trinh vat
ly va tinh the xay ra
tronu
cong nghe HDDR da dugc thuc hien d nhieu noi
tren the gidi va cho cac
kci
qua kha tudng minh. Chinh vi vay d day chiing
tdi chi tap
truiig
vao
kliao sal
cac dieu kien va cac thdng sd cdng nghe nham
tim dugc quy trinh
cdny riyhe
thich hgp tuong irng vdi he thdng thiet bi hien
cd, cho phep che tao
duxic
cac nam cham ket dinh cd nang lugng cao, phan
ly giai chi
dii'ng

lai d
thao luan
dinh tinh cd the chap nhan dugc.
linh
1.
Anh
chnn '< rrofJuid
theo mat
celt
doc
(a)
vd ngang (b)
ciui
li'.h'
kim
Nd/r^Fe-o.^Zr^Bs
v61
x
0.
J
17
OAI
HOC
QMOC
O'^
HA
NO)
Cac hgp kim ban dau
Ndi6Fe76.xZrxB8
vdi x

=
0, 0.1, 0.2, 0.3, 0.5 dugc
che tao bang phuong phap ndng chay hd quang, trong mdi trudng khi Ar tir
cac nguyen lieu ban
d4u
cd do sach tdi
thilu
la 99,9%. Hgp kim sau khi
n4u
cd mau xam sang, be ngang mau thay rd
c4u
true textua theo hudng vudng
gdc vdi day ndi. Kiem tra cau tnic ddmen
ciia
cac mat cat dgc theo phuong
textua (a) va vudng gdc vdi phuong textua (b)
bSng
chk
Idng
tir (ferrofluid)
f f
,
cho ta thay (hinh 1) d hinh (a) cau tnic ddmen tir cd dang dieu xi ga cdn d
hinh (b) cd dang cac bgt tir, cho thay ddmen tir ciing xap xep theo phuong
textua. Nhu vay cac hat tinh the dugc djnh hudng tuong ddi ddng nhk theo
mot phuong tinh the.
\
f f
it^
Sau khi dap nhd bang cdi sat, cac mau hgp kim cd kich thudc khoang

1-^3
cm dugc dua vao budng phan ung. Sau khi hut chan khdng dat gia tri
f
y
\
f
chan khdng so cap, ddng thdi vdi viec hut chan khdng bang bom khuech tan,
•>
\
ft
Id
boat ddng de nang nhiet do budng phan ung len den
lOO^C
vdi tdc do
nhiet la
6°C/
phiit. Khi dat chan khdng cao
5x10"^
mbar,
hydro dugc dua vao
budng phan
ling
tir budng luu giir hydro bang bdt
LaNi5
cho tdi ap suat
f
\
f
\ \
hydro xap xi bang 1 atm. Bat dau tir day, nhiet do cua budng phan img dugc

thay ddi theo mot chuong trinh nhiet xac djnh
tiiy
theo timg me mau.
3.1.
He mau hgp kim
Ndi6Fe76B8
He mau
NdieFcyeBg
da dugc xu ly nhiet theo cac quy trinh nhiet khac
nhau va dugc ky hieu tuong ung
la^Mla,
Mlb
va
Mlc.
Vdi he mau cd ky hieu
Mia,
quy trinh sir ly nhiet dugc thuc hien nhu
>
->
> >
tren so dd hinh
15.
O qua trinh
dau.
Id
boat ddng nang nhiet do budng phan
ung tir nhiet do phdng
Troom len
tdi
lOO'^C

vdi tdc do la
6°C/phut
(tdc do nay
phii
hgp vdi qua trinh vira bom chan khdng vira tang nhiet do cho budng
phan irng). Khi budng phan ung dat do chan khdng cao
5x10"^
mbar, hydro
18
dugc lay tir budng luu
trii
hydro dua vao buong phan ung cho tdi ap suk
t
T(^C)
800X
6^'C/phut
20=C/phut
Theo
16
8^C/phut
26^C/phut t
Hinh 2. Quy trinh nhiet cua mdu
Mia.
hydro xap xi bang
latm,
bat dau cho nhiet do cua budng phan ung tang len
tdi
200°C
vdi tdc do tang nhiet la
20°C/phut;

rdi
dk
nhiet do tang theo id
nung len tdi
700°C;
nhiet do tiep tuc dugc tang len tdi
800°C
vdi tdc do tang
nhiet la
8°C/phut
va
giiJ
budng phan img tai nhiet do nay trong vdng 2.5 gid.
Sau qua trinh giir nhiet, budng phan img dugc giam nhiet do xudng
200°C
f f
\
tuong ling vdi tdc do
200°C/phiit
va cudi ciing budng phan ung dugc giam
r
f f
xudng den nhiet do phdng
Troom
vdi tdc do giam nhiet la
26°C/phut.
Quy trinh nhiet
ciia
mau Mlb, budng phan img dugc tang nhiet do tir
nhiet do phdng

Troom
l^n
tdi
800°C
va dugc
giir
tai nhiet do nay trong 2.5 gid
la hoan toan tuong tu nhu ddi vdi quy trinh nhiet cua mau
Mia,
nhung sau
f •>
qua trinh nay thi tat
id
va hut chan khdng de ngudi theo
Id.
Ddi vdi he mau
Mlc
thi quy trinh nhiet ciing tuong tu nhu quy trinh
nhiet cua he mau
Mlb
nhung chi tang nhiet den nhiet do cao nhat la
700''C,
sau dd giir trong 2.5 gid rdi de ngudi theo
Id.Sau
khi thuc hien xong quy
trinh HDDR, cac mau deu dugc nghien nhd bang may nghien bi, rdi phan
19
loai hat theo hai loai: d <
100)im
va d >

lOOjim bang
may ray. Bdt vat lieu
HDDR dugc trdn vdi epoxy
r^n
vdi ty le 2% trgng lugng, roi dugc ep trong
' T(^C)
100=C
200=0^^
700X
^ *
800"'C
Giur
trong
2.5 gid
Ngupi
theo to
6^C/phut
20X/phiJt
Theo
16
8^C/phut
t
Hinh 3. Quy trinh nhiet cua mdu
Mlb.
r
f
'y
f
khudn thep
((t)12

hoac
(t)15
mm) vdi ap suat 6 tan/cm . Tiep theo dd la
polymer hda trong nhiet do
125°C/gid,
cac mau dugc nap tir trong tir trudng
xung 5 Tesla, sau dd dugc xac dinh cac thdng sd cua nam cham. Cac thdng
sd cua he mau
Ml
(a, b, c) dugc
liet
ke trong bang
1.
Bang 1. Cdc thong so cua he mdu Ml
MIU
Mia
Mlb
Mlc
d(}im)
<100
>100
<100
>100
<100
>100
P
[g/cm^]
5.5396
5.8056
5.5907

5.7930
5.5367
5.7355
Br
[KG]
4.2
4.04
4.05
4.1
3.98
4.04
MHC
[KOe]
7.78
7.55
7.95
•
8.03
7.54
7.60
BHC
[KOe]
3.15
3.12
3.10
3.25
3.10
3.25
(BH)max
[MGOe]

3.36
3.33
3.45
3.61
3.32
3.36
Tir bang cac thdng so cua he mau Ml, ta nhan thay rang, trong ca 3
oai
mlu,
vdi cac hat cd kich thudc d >
lOOfim ludn
cho ket qua tdt hon so
20
vdi
mau cung loai co
kich thuac
hat d <
lOO^m.
Di^u
nay co
thi
la do
nghien be mat cac hat
Ion
it bi go ghe hon cac hat nho do do it xuat hien cac
domen
ngugc ichur tir
tinh
ciia
hat, bieu hien ra la gia tri

lire
khang
tir
va gia
tri tir du ndi chung vdi d >
lOO^im dku Idn
hon.
Ta
cQng
nhan thay rang, cac ket qua
v^
nam cham da dugc cai thien
dang ke, tuy cac gia tri nay van cdn thap so vdi
cacjcet
qua da dugc cdng bo
la 5 MGOe ddi vdi loai HDDR ding hudng (cd mot ket qua da cdng bo cua
T(^C)
100=C
IOO'CJ/^
700=0
y^
X
= 750, 810 or
850'^C
•x>
\
en '^ \
m
O \
1

i
\
^
2
6X/phut 20X/phut
Theo
16 8X/phut t
Hinh 4. Quy trinh nhiet
ciia
mdu M2.
nhdm Takeshita,
(BH)max ciia
loai nay len tdi 8 MGOe nhung khdng ndi rd
ve cac dieu kien vat lieu).
t
f
"w
De cai thien cac ket qua da dat dugc, mot he mau mdi da dugc sir
dung de khao sat ty mi hon quy trinh nhiet, he M2. Quy trinh nhiet cho he
mau nay dugc chon gidng nhu quy trinh nhiet cua mau
Mlb,
nhung thay ddi
gia tri nhiet do cao
nh4t
la:
750°C,
810°C
va
850^C
tuong img vdi ky hieu a,

b,
c vdi thdi gian
giij
nhiet la 3 gid va do hat dugc
lira
chon bang may ray
cd: 100
|Lim
< d < 125
^m.
Cac ket qua cua he mau nay dugc tdng hgp trong
bang 2.
21
Bang 2. Cdc thong so cua he mdu M2.
MIU
M2a
M2b
M2c
P
[g/cm^]
5.8432
5.9107
5.8502
B.
[KG]
4.69
5.08
4.41
MHC
[KOe]

8.50
8 38
8.54
BHC
[KOe]
3.08
3.15
3.20
(BH)niax
[MGOe]
4.13
4.58
4.15
f f
•\
T
Tir bang ket qua tren ta nhan thay rang, vdi nhimg thay ddi chinh la do
hat cd 125
|j.m
va tuong ddi ddng deu trong khoang
100-^125
|im,
thdi gian
giir d nhiet do cao nhat thay ddi dai hon (3 gid), ket qua mau M2b thu dugc
da dat dugc gia tri thdng thudng van cdng bd ve loai bdt HDDR dang hudng
nay. Ta thay rang gia trj
BHC
gan nhu khdng thay ddi nhung gia
tri Br
co

tang, cd
th§
la do do hat ddng deu hon, thdi gian tach pha va tai hgp dai hon
cho phep phan ung xay ra hdan tdan tren toan bd the tich mau. Nhu vay quy
trinh nhiet cho mau M2b la quy trinh nhiet thich hgp nhat vdi lugng mau
khoang 30 gam, dat dugc
(BH)niax ^
4.58 MGOe.
D§
nang cao
ch4t
lugng bdt vat lieu, can phai lam the nao dd de bdt
tao ra
bang
phuong phap nay trd thanh bdt di hudng, chimg tdi da chon
phuong phap pha tap vao hgp kim NdFeB mot lugng Zr de cd dugc hgp kim
Ndi6Fe76-xZrxB8
vai x = 0.1, 0.2, 0.3, 0.5. Cac ket qua cua cac he mau nay se
dugc
trinh bay trong phan sau.
3.2. He mau
ho-p
kim
NdieFeTe-xZr.Bg vdi
x = 0.1, 0.2, 0.3, 0.5
He mau
NdieFcye-xZrxBg
dugc xu ly nhiet tuong tu nhu quy trinh xu ly
nhiet cua he mau M2b va dugc ky hieu la M3a, M3b, M3c, M3d
tuomg

ung
vaix
= 0.1,0.2, 0.3, 0.5.
22
Tuong tu nhu doi voi cac he mau Ml va M2, sau khi thuc hien xong
quy trinh HDDR, cac mau
d§u
dugc
nghien
nho
bang
may
nghiln
bi, rdi
toom
810=C
x>
a»
m
at
c
9
^-f
i^
o
-o
o
i the
<o
3

^
6=*C/phut 20=C/phut
Theo
16
8^'C/phut
|.
Hinh 5. Quy trinh nhiet cua mdu M3.
phan loai hat bang may ray cd dudng kfnh
lOOjim
< d <
125|im.
Bdt vat lieu
HDDR dugc trdn vdi epoxy
rSn
vdi ty le 2% trong lugng, rdi dugc ep trong
khudn thep
{^\3
mm) vdi ap suat 6
t§n/cm^
trong tir trudng 1 Tesla, song
song vdi phuong ep.
TiSp
theo dd la polymer hda trong nhiet do
125''C/gid,
cac mau dugc nap tir trong tir trudng xung 5 Tesla, sau dd dugc xac dinh cac
thdng sd
ciia
nam cham.
Cac thdng sd
ciia

he mau dugc tdng ket trong bang 3. Tir cac ket qua
thu dugc ta thay ring vdi thanh phan hgp kim pha tap
0.1
% Zr (x
=
0.1)
cho
cac ket qua tdt nhk, dat tich nang lugng
(BH)rnax
cao nhk 7.09 MGOe. Tuy
nhien, gia tri nay cdn thap so vdi ket qua ma mot sd cdng trinh cua cac tac
gia khac da dat dugc tren ciing loai bdt HDDR di hudng.
23
Mau
M3a
(x=0.1)
M3b
(x=0.2)
M3c
(x=0.3)
M3d
(x=0.5)
Happ — 0
l^app
~ 1
Happ —
0
Happ =
1
Happ —

0
Happ
= 1
Happ =
0
'"lapp ~ ^
Bang;
p[g/cm^]
5.9249
5.9197
5.8398
5.8429
5.8511
5.8609
5.8327
5.8617
3.
Cdc thong so
ciia
mdu M3
Br
[KG]
5.1
5.79
4.7
5.55
4.49
5.69
4.41
5.37

MHC
[KOe]
9.4
9.61
8.49
9.72
8.6
9.49
8.5
9.63
BHC
[KOe]
4.01
4.86
3.1
4.72
3.3
4.79
3.2
4.62
(BH)max
[MGOe]
5.2
7.09
4.25
6.88
4.41
6.87
4.2
6.24

H/B
at
(BH)„ax
0.3
0.32
0.29
0.35
0.29
0.35
0.37
Do vay, he mau
M3a
da dugc chon de khao sat quy trinh nhiet ti mi
hon. Quy trinh nhiet cho he mau nay dugc chon nhu ban dau nhung thay ddi
nhiet do cao
nhat
la:
800°C
(M3al),
820°C
(M3a2),
830^C
(M3a3) va
850°C
(M3a4), thdi gian
giii
tai nhiet do cao nhat nay van la 3 gid. Cac ket qua cua
he mau nay dugc dua ra trong bang 4.
Tir cac kk qua d bang 4, ta nhan thay rang, ddi vdi viec pha tap Zr,
X =

800,
820,
830 or
850X
O
6^C/phut
20-~C/phut
Theo
16
8^C/phut
t
Hinh 6. Quy trinh nhiet
ciia
he mdu M3al, M3a2, M3a3 vd M3a4
24
max
nhiet do cao
nhSt
cua quy trinh nhiet tang len lam tich nang lugng (BH)
tang (dat 9.23 MGOe), mat do tang, ddng
thdi
do djnh huong cung tang
thi
hien qua he s6 vuong ty le tang khi nhiet do cao nhat tang.
DiSu
nay cung co
the la do Zr co nhiet do nong chay cao
(2125K)
nen thich hgp voi viec nhiet
do xu ly cao.

Bang 4. Cdc thong so cua mdu
M3al,
M3a2, M3a3 vd M3a4
Mau
M3al
M3a2
M3a3
M3a4
Nhiet do
li
[°C]
800
820
830
850
p[g/cm^]
5.9202
5.9197
5.9257
5.9580
Br
[KG]
5.81
5.89
6.43
6.67
MHC
[KOe]
9.60
9.72

9.68
9.76
BHC
[KOe]
4.8
5.01
5.41
5.48
(BH)niax
[MGOe]
7.2
7.80
9.05
9.23
H/B
at
(BH)max
0.32
0.33
0.4
0.35
' ' f 1
Vay neu ta chon che do thdi gian dai hon tai nhiet do cao nhat, cd the
dat dugc nhimg ket qua nhu mong dgi. Chinh vi ly do nay cac he mau M3a3
va M3a4 da dugc chon de khao sat
sir
thay ddi thdi gian giir nhiet tai nhiet
do cao nhat, vdi thdi gian giir nhiet la 3.5 va 4 gid. Ta se cd cac he mau
tuong ling:
M3a31,

M3a41
(giij
trong 3 gid); M3a32, M3a42 (giir trong 3.5
gid);
M3a33, M3a43
(giij
trong 4 gid). Cac ket qua cua he mau nay dugc
dua ra trong bang 5.
X = 830 or
850'^C
6^C/phut
20^C/phut
Theo 16
8"C/phut
Hinh 7. Quy trinh xu ly nhiet
ciia
he M3a3 vd M3a4
25
Bang 5. Cdc thong so
ciia
mdu
M3a31,
M3a32,
M3a33,
M3a41, M3a42
vd^M3a43
MIU
M3a31
M3a32
M3a33

M3a41
M3a42
M3a43
pCg/cm^]
5.9257
5.9318
5.9507
5.9580
6.0011
6.0020
Br
[KG]
6.43
6.68
6.44
6.67
6.92
6.66
MHC
[KOe]
9.68
9.63
9.69
9.75
9.79
9.79
BHC
[KOe]
5.41
5.52

5.28
5.48
5.67
5.57
(BH)niax
[MGOe]
9.05
9.31
8.68
9.23
9.95
9.46
H/B
at
(BH)„ax
0.4
0.35
0.34
0'.35
0.35
0.38
f
r \
Tir cac ket qua dua ra trong bang 5 ta nhan thay rang, khi tang thdi
f
gian
giir
nhiet d nhiet do cao nhat len thi tinh tir cung
ciia
vat lieu da dugc

cai thien dang ke the hien d chd la tir du
Br
tang va luc khang tir
He
tang.
f f r
f
Cac ket qua tdt nhat dat dugc ddi vdi thdi gian giir nhiet la 3.5 gid. Khi thdi
gian
giir
nhiet la qua dai, trong 4.5 gid, lai lam giam tinh tir cimg cua vat lieu
tuy la khdng nhieu. Hieu qua
ciia
hieu img nhiet cao the hien rd nhat tren he
r^
f
t
mau M3a42, cac ket qua dat dugc rat kha quan, tich nang lugng
cue
dai dat
dugc la 9.95 MGOe.
Vdi he mau nay, thdi gian dai va nhiet do cao lam cho qua trinh tach,
nhap pha
Nd2Fei4B
xay ra hoan toan tren toan bd the tich mau va cd the lam
r \ f
cho kich thudc hat
Idn
hon tien gan den kich thudc tdi han cua don ddmen
(chi cd 0.3

^im).
Do dd, anh hudng
ciia
muc do ghd ghe tren be mat mdi hat
giam di gdp phan cai thien gia tri tir du
Br ciia
he mau.
Tir cac ket qua
ciia
hgp kim NdFeB khi khdng cd pha tap va khi cd
pha tap Zr vdi
ph4n
tram khac nhau, ta thay rd anh hudng
ciia
viec pha tap
Zr vao he hgp kim. Hieu img pha tap nguyen td Zr da lam phuc hoi tinh dj
hudng cua vat lieu. Nguyen nhan la do vat lieu ban dau da cd tinh di hudng,
26