Brazing of Titanium Using
Low-Melting-Point Ti-Based Filler Metals
A new amorphous foil is developed that allows brazing below
the transformation temperature of titanium
BY T. O N Z A W A , A. S U Z U M U R A A N D M . W . K O
ABSTRACT. The microstructure and mechanical properties of commercially pure
titanium (CPTi) and Ti-6AI-4V alloy joints
brazed with newly developed Ti-based
amorphous filler metals were investigated
by microscopy, electron probe microanalysis, tensile test, fatigue test and salt
immersion test. Among the developed
filler metals, three kinds of Ti-37.5Zr15Cu-10Ni, Ti-35Zr-15Cu-15Ni and Ti25Zr-50Cu alloys were used in this study,
whose melting points were approximately
100°C (180°F) lower than those of conventional Ti-based filler metals.
In brazing below a-/? transformation
(880°C, 1616°F) or 0 transus (990°C,
1814°F) temperature of the base metals,
the original fine grains of the base metals
were completely preserved, and the
brazed zone was distinct from the base
metal. On the contrary, in brazing above
these transformation temperatures, the
grains of the base metals were coarsened,
and fine Widmanstatten structure was
formed at the joint area. These joint
structures were related to the mechanical
KEY W O R D S
Brazing of Titanium
Low Melting Point
Ti-Zr-Cu-Ni Filler Metals
Filler Metal Development
Ti-6AI-4V Base Metal
Amorphous Filler Metal
Ti-Based Amorphous
Transformation Temp
Corrosion Properties
Joint Fatigue
T. ONZAWA, A. SUZUMURA andM. W. KO
are with the Department of Mechanical Engineering for Production, Tokyo Institute of Technology, Tokyo, lapan.
Paper presented at the 19th International AWS
Brazing and Soldering Conference, held April
19-21, 1988, in New Orleans, La.
462-s | DECEMBER 1990
properties of the joints. Especially in the
case of the Ti-6AI-4V joint, the formation
of fine Widmanstatten structure deteriorated the ductility of the joint.
In the tensile test, CPTi and Ti-6AI-4V
alloy joints brazed with Ti-37.5Zr-15Cu10Ni alloy at 850°C (1262°F) for 5 min and
at 900°C (1652°F) for 10 min, respectively, were fractured in the base metals.
The fatigue properties of TE6AI-4V joints
brazed at 900°C (1652°F) for 10 min were
equal to that of the base metal at maximum stresses below 590 MPa (85.5 ksi).
Furthermore, after immersing in 5% NaCI
solution up to 1000 h, no reduction in
tensile strength of the joints occurred.
These results demonstrate that the use of
these newly developed low-melting-point
filler metals make it possible to braze
without a-p transformation and /3 transus
of CPTi and Ti-6AI-4V base metals, respectively, which results in joints with excellent mechanical properteis and corrosion resistance.
metals are generally above 900°C
(1652°F), so that such brazing temperatures higher than the a-(3 transformation
temperature of CPTi and comparable to /3
transus temperature of titanium alloys are
required. In brazing at these temperatures, the mechanical properties of base
metals, such as ductility and toughness,
are impaired because of the phase transformation and coarsening of grains of
base metals that occur during the brazing
cycles. Because it is difficult to make these
filler metal alloys into foils due to low
workability, they have been commonly
used in powder form or as laminated
brazing foils (Refs. 5, 7, 8).
Therefore, this study was undertaken
to develop Ti-based amorphous foil filler
metals that would make it possible to
braze below a-0 transformation and /3
transus temperatures of CPTi and Ti-6AI4V base metals, respectively.
Materials and Procedure
Introduction
Materials
Brazing of titanium and its alloys has
been studied extensively, and it has been
known that silver-based filler metals (Refs.
1-3), such as Ag-Cu-Ni-Li; titanium-based
alloys (Refs. 4-8), such as Ti-Cu-Ni; and
aluminum and its brazing sheet (Refs.
9-11), are excellent in wettability and mechanical properties, and that pure copper
is suitable particularly for diffusion brazing
(Refs. 12-14).
Among these filler metals, Ti-based filler
metals are superior in high-temperature
strength and corrosion resistance of the
joint (Refs. 4, 5, 7). However, the melting
points of the conventional Ti-based filler
Commercially pure titanium (CPTi) and
Ti-6Al-4V alloy were prepared as base
metals, where the Ti-6Al-4V alloy was annealed at 700°C (1292°F) for 1 h after
forging, and has an equiaxed structure.
Tables 1 and 2 give the chemical compositions and mechanical properties of these
base metals.
As for brazing filler metals, three of the
Ti-Zr-Cu-Ni amorphous foils and a commercial Ti-Cu-Ni laminated foil shown in
Table 3 were used. Besides these, silverbased filler metals of Ag-15Cu, Ag-28Cu2Ti, Ag-28Cu-0.2Li alloy were also provided for comparison.
Table 1—Chemical Compositions of Base Metals Used (wt-%)
Materials
Ti
CPTi<a>
TF6AI-4V
bal
bal
Al
Fe
6.07
0.090
0.140
(a) CPTi - commercial pure titanium.
4.12
O
0.011
0.010
0.090
0.180
0.0018
0.0020
0.007
0.010
Brazing and Experimental Procedure
T h e ends of cylindrical specimens w e r e
m a c h i n e d flat and parallel, and w e r e p o l ished w i t h metallographic papers u p t o
2000 grit. Immediately p r i o r t o placing t h e
brazing filler metal b e t w e e n t h e mating
surfaces of t h e specimens into t h e brazing
c h a m b e r , t h e specimens w e r e degreased
a n d rinsed w i t h a c e t o n e . T h e c h a m b e r
was evacuated up to approximately 8
M P a (6 X 1 0 - 5 t o r r ) , a n d t h e n i n d u c t i o n
heating of t h e specimens w a s started. T h e
specimens w e r e h e a t e d t o t h e desired
t e m p e r a t u r e s in less t h a n 3 m i n . D u r i n g
brazing, t h e specimens w e r e c o m p r e s sively l o a d e d b y 1 M P a (145 psi), a n d w e r e
isothermally held at fixed t e m p e r a t u r e s .
At t h e e n d of the time p e r i o d , the induct i o n g e n e r a t o r w a s s t o p p e d . T h e specimens w e r e a l l o w e d t o c o o l t o b e l o w
1 5 0 ° C (302°F) in t h e v a c u u m c h a m b e r .
A f t e r brazing, t h e as-brazed samples
w e r e w o r k e d into such shapes as s h o w n
in Fig. 1 a n d w e r e s u b j e c t e d t o microsc o p y , e l e c t r o n p r o b e microanalysis, t e n sile tests at r o o m a n d e l e v a t e d t e m p e r a tures, fatigue test and salt immersion test
in 5% NaCI at 3 5 ° C (95°F).
each alloy b y a p p r o x i m a t e l y
100°C
(180°F). This suggests that the addition o f
these elements t o Ti-Cu-Ni filler metals is
also e f f e c t i v e in decreasing their melting
points. T h e r e f o r e , in o r d e r t o c o n f i r m the
e f f e c t , z i r c o n i u m and v a n a d i u m w e r e
a d d e d t o Ti-Cu-Ni alloys.
I2
u
W
a
C
Various kinds of Ti-Zr-Cu-Ni alloys c o n taining t h e same p r o p o r t i o n o f titanium
a n d z i r c o n i u m w e r e p r o d u c e d using an
arc f u r n a c e in an argon a t m o s p h e r e . As a
result of measuring the liquidus and solidus
o f these alloys, the l o w e s t melting p o i n t
w a s a b o u t 8 0 0 ° C (1472°F), as s h o w n in
Table 3, w h i c h is a p p r o x i m a t e l y 1 0 0 ° C
(180°F) l o w e r t h a n that of Ti-Cu-Ni alloys.
Several l o w - m e l t i n g - p o i n t alloys w e r e sel e c t e d , a n d w e r e m a n u f a c t u r e d b y melt
q u e n c h i n g into a m o r p h o u s foils of 4 0 - 6 0
(im in thickness a n d 5 m m (0.197 in.) in
w i d t h . A m o n g t h e m , t h r e e foil c o m p o s i tions w e r e used in this e x p e r i m e n t , a n d
are listed in Table 4. As f o r the a d d i t i o n o f
v a n a d i u m t o Ti-Cu-Ni alloy, n o l o w - m e l t ing-point alloys c o u l d b e o b t a i n e d w i t h i n
this investigation.
u
c
25
75
3
C
100
(a)
a
T e n s i l e T e s t Specimen
(Room T e m p e r a t u r e )
a
ti
17 .
>•*.
h
2
u
E
a
30
C
J0_
I
100
u
C
(b) Tensile Test Specimen
(Elevated Temperature)
Results and Discussion
Ti-Cu-Ni alloys, as w e l l as Ti-Zr-Be alloys, are representative Ti-based filler m e t als f o r brazing o f titanium, a n d h a v e b e e n
used c o n v e n t i o n a l l y in the f o r m o f p o w der or laminated brazing foils (Refs. 5, 7).
M o s t of these filler metals h a v e brazing
t e m p e r a t u r e s s o m e w h a t higher than d e sirable. As k n o w n in Ti-Zr a n d Ti-V equilibrium b i n a r y phase diagrams (Refs. 15),
the a d d i t i o n of 50 w t - % Zr o r 32 w t - % V
t o titanium reduces the melting p o i n t of
•s.
I
C
a
<
u
M10-P1.0
V.
u,
Metallurgical Examination
Development of Filler Metal
<
u
II
u
a
Figure 2 exhibits the m i c r o s t r u c t u r e of a
CPTi joint b r a z e d w i t h Ti-25Cu-15Ni laminated filler m e t a l . T h e grains o f the base
metal are c o a r s e n e d , a n d the b r a z e d
region consists of fine W i d m a n s t a t t e n
structure, w h i c h is typical in CPTi joints
b r a z e d w i t h c o n v e n t i o n a l Ti-based filler
metals a n d is similar t o that in diffusionb r a z e d joints using p u r e c o p p e r filler
metal (Refs. 4 , 14).
Figure 3 s h o w s the microstructures a n d
electron p r o b e microanalyses of CPTi
H
Z
Li.
5
a
—
C
LL
(mm)
(c)
Fatigue Test
Specimen
Fig. 1 — Shapes and dimensions of test specimens. A — Tensile speciman for room temperature; B— Tensile speciman for elevated temperature; C —Fatigue specimen.
>
LL
c
I
c
a.
<3
i*
LL
a
h
z
Table 2—Mechanical Properties of Base
Metals Used
LL
Materials
CPTi
TF6AI-4V
Tensile strength (MPa)
360
1060
Reduction of area (%)
67
41
Elongation (%)
42
18
s
a
c
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C
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a
h
- • ' . - '•••••• ••••"*
ZrLa
z
u
s
a
CuKa
L::=.',: $ WWfrt
•'•••
•*
*
,
Um
lOOum
i
Fig. 2 — Microstructure
of CPTi joint brazed
with Ti-25Cu- 15Ni laminated filler metal (980° C,
5 min).
>
LL
lU
1
0L
C
u.
NiKa
Fig. 3 - Microstructures and electron probe microanalyses of CPTi joints brazed with Type 1510 filler
metal. A - 850°C, 5 min; B- 1000°C, 5 min.
c
c
a
I
<J
LL
ir.
LL
a
WELDING RESEARCH SUPPLEMENT 1463-s
joints brazed with Type 1510 filler metal.
The joint brazed at 1000°C (1832°F)
above a-|8 transformation temperature of
the base metal (Fig. 3B) has almost the
same structure as that shown in Fig. 2. O n
the other hand, when brazed at 850°C
(1562°F) below the transformation temperature, the original structure of the base
metal is completely preserved, though the
brazed region with coarse acicular structure is distinct from the base metal, as
shown in Fig. 3A. The maximum residual
copper and nickel contents at the center
of the brazed region were reduced to
Fig. 4 - Transmission electron micrographs of CPTi joint brazed by cooling immediately after heat-20% of that in the filler metal as calculated
ing to 850°C (1562°F). A —interface between base metal and brazed region; B —brazed region.
from the results of electron probe microanalysis.
f — ; T - T T ' 7-^ ::- 'S
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-ifl
Figure 4 exhibits transmission electron
micrographs of a CPTi joint made by
cooling immediately after heating to a
brazing temperature of 850°C (1562°F).
As a result of observation and electron
diffraction of the white phase at the interface between brazed region and base
metal, the configuration and lattice constant shown in Fig. 4A were revealed to be
different from those of original a phase in
the base metal. This suggests that the base
metal is rapidly dissolved by the molten
filler metal. On the other hand, the brazed
region in Fig. 4B consists of fine eutectoid
structures, which are forming colonies
with cell, rod and lamellar structures.
I-*'.- Si'.'?"- , ** ,a^!ip
~v *"\S
-<
•' fv^
Lv » "
l> > - * i
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-
.
••-»..-
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These results indicate that the base
metal was probably dissolved by the molten filler metal with the dilution of each element in the filler metal, and subsequently
pearlite-like structures were formed in the
brazed zone by eutectoid reaction.
Figure 5 shows the relation between
brazing temperatures and microstructures
Fg. 5 — Relation between brazing temperatures and microstructures of CPTi joints brazed with Type of CPTi joint with Type 1510 filler metal.
The microstructure of the joint brazed at
1510 filler metal. A -860°C, 5 min; B-870°C, 5 min; C-8WC, 5 min; D-890°C 5 min.
860°C (1580°F) is almost the same as that
shown in Fig. 3A with an obvious brazed
-'-. ' ' ' '" -'-.'.-Vy.^.zone. In the joint brazed at 870°C(1598°F)
slightly above the a-j3 transformation temperature of the base metal, the brazed
region becomes obscure and a fine Widmanstatten structure appears. At temper5*5
atures above 880°C (1616°F), the joint
region consists of fully fine Widmanstat77 ;
ten structure, where the width of the
zone is expanded beyond 150 ^ m , acvJOs;.^-'
•tv7)
«( 25um
i25um
companied by a coarsening of the base
i
i|
metal grains.
. • .7,-7 • •* ,- - > ^ 2 ? v « .
fiOgB
90rJfM^W^
—'—'3
These results demonstrate that the brazing at above transformation temperatures
results in the fine Widmanstatten structure
20r
at the joint region.
0
ZrLa
As for Ti-6Al-4V joints, microstructures
and electron probe microanalyses of the
2
joints brazed with Type 1510 filler metal
are revealed in Fig. 6. In the joint brazed
0
CuKa
at 900°C (1652°F) shown in Fig. 6A, the
25pm
original fine structure of the base metal is
preserved, and the brazed region consists
^ > V
Wwow^NiKa0 tww*^
of fine acicular structure. When brazed at
950°C
(1742°F) (Fig. 6B), the width of the
F/g. 6—Microstructures and electron probe microanalyses oiTi-6Al-4V joints brazed with Type 1510
brazed region is expanded, and the ratio
filler metal. A - 900"C, 5 min; B-950°C, 5 min.
[ Si yi*V,
464-s | DECEMBER 1990
of primary a phase increases in the base
metal. When brazing at 1000°C (1832°F)
above /? transus temperature of the base
metal, grains of the base metal were
remarkably coarsened, and the fine Widmanstatten structure was observed in the
joint.
Tensile Strength of Joints
Before the mechanical properties of the
joints brazed with the developed Ti-based
filler metals were investigated, tensile tests
on the joints made by using three kinds of
conventional Ag-based filler metals and
Ti-25Cu-15Ni laminated brazing foils were
carried out. It can be seen from Fig. 7 that
the joints brazed with Ti-Cu-Ni filler metal
had higher strength than that with Agbase filler metals. Nevertheless, in spite of
brazing at the considerably high temperature of 980°C (1796°F), all specimens
brazed with the Ti-Cu-Ni filler metal fractured in the brazed zone, exhibiting fairly
low ductility.
Figure 8 shows the tensile test results of
CPTi joints at room temperature in comparison with the brazeability of three kinds
of Ti-Zr-Cu-Ni filler metals. In the case of
brazing at above 900°C (1652°F), all the
joints are fractured in the base metal.
Though the tensile strength is slightly decreased and the reduction of area is conversely increased, these properties are almost the same as that required for the
base metal without heating. As already
mentioned, brazing at above a-fi transformation temperature of CPTi results in
coarsening the base metal grains. However, in brazing with these filler metals, a
joint having homogeneous composition
can be obtained even by heating for a
short time, so that the undesirable effects
of this high-temperature heating is considerably lessened. Particularly in the case
of using Type 1510 filler metal, tensile
strength and ductility of the joint brazed
even at 850°C (1562°F) below the transformation temperature are both equal to
those of the base metal.
Figure 9 shows the relation between
brazing temperature and tensile properties of Ti-6AI-4V joints brazed with Ti-ZrCu-Ni filler metals. As compared with the
considerably low tensile strength of the
joint made at 850°C (1562°F), the
strengths of the joints brazed at 900°C
(1652°F) are improved enough to be
equivalent to that of the base metal, in
spite of failing at the joint interface.
The joint brazed with either Type 1510
or Type 1515 filler metal demonstrated
sufficient tensile properties comparable to
those of the base metal. On the other
hand, all the joints made at 1000°C
(1832°F) above /3 transus temperature
railed in the base metal, and the ductility
of the base metal is deteriorated considerably by the brazing thermal cycle.
The effects of holding time at the braz-
ing temperature on tensile properties of
Ti-6AI-4V joints are shown in Fig. 10. In the
case of brazing at 850°C (1562°F), even
the joint made by heating for 30 min has
poor tensile properties. On the contrary,
tensile properties of the joints made at
900°C (1652°F) are improved with the increase in holding time, and all the joints
failed in the base metal after heating 10
min.
From the above results, though the
tensile properties are greatly affected by
brazing temperature and time, the filler
metals bearing nickel are considered to be
rather excellent.
1 Base Metal : CP Ti
500 -
£
Base Metal
400
"
-A
V
300D-~-.
o
Table 3—Chemical Compositions, Solidus
and Liquidus of Ti-Zr-Cu-Ni Alloys
fiquidus
Ti
45.0
42.5
40.0
37.5
Zr
45.0
42.5
40.0
37.5
36.0
36.0
35.0
35.0
32.5
30.0
27.5
25.0
(°Q
Solidus
(°C)
5
810
780
5
800
790
5
10
820
800
15
5
815
795
10
If)
830
805
5
15
825
795
15
10
815
805<a>
32.5
30.0
27.5
25.0
15
840
815
0
28
880
820
15
15
820
770<a>
5
25
870
840
20
15
890
830
15
20
860
835
•
u
1
Base
825
o 40
880
20
20
20
870
840
15
25
855
830
815
990
970
10
35
1035
50
0
815
780<a>
25
25
980
860
Metal
;
*
=
•
•
=
•
Type 1510
0---0
Type 5000
Failed in Base Metal
S 60
860
840
10
Time (min)
a—a Type 1515
J2 100
900
1030
830'C
830'C
Time : 5 min
oF'
'200
25
5
D BAg8a
Base Metal: CP Ti
Brazing
30
15
,920'C
BAg8(Ti)
Fig. 7—Strength of CPTi joints brazed with Tibased and Ag-based filler metals.
5
30
Ag-15Cu
5
Holding
10
40
fi
v~-^
£'300-
10
OTi-25Cu-15N , 980°C
O
100
Ni
5
" \ ^
A-
Cu
10
200
850
900
950
1000
Brazing Temperature
(°C )
Fig. 8 — Relation between brazing temperature
and tensile properties of CPTi joints brazed
with three kinds of Ti-Zr-Cu-Ni filler metals.
1200-
Base M e t a l : T i - 6 A I - W
B r a z i n g Time : 5 m i n
IO0C-"
T ^ Z T ^
(a) Materials used n brazing
i 600-
Table 4—Chemical Compositions of Brazing
Filler Metals Used (wt-%)
Materials
Type
1510(a)
Type
1515(a)
Type
5000(a)
Ti-CuNi(b)
Ti
Zr
Cu Ni
eoc-
Liquidus Solidus
(°C)
(°Q
37.5 37.5 15 10
815
805
35
35
15 15
820
770
25
25
50
—
815
780
bal
—
25
15
930
—
Type 1510
a—a T y p e l 5 1 5
O — O Type 5000
A . • F a i l e d i n Base Metal
20C
850
(a) Amorphous brazing filler metal.
(b) Laminated brazing filler metal.
900
Brazing
950
Temperature
1000
(°C )
Fig. 9 — Relation between brazing temperature
and tensile properties of TI-6AI-4 V joints brazed
with Ti-Zr-Cu-Ni filler metals.
WELDING RESEARCH SUPPLEMENT 1465-s
"
Base Metal : Ti-6AI-4V
Brazing Temprature : 850°C, 900*C
1200
Type 1510.900C
Type 1510,850*C
a—a Type I515,900°C
O - . - o Type 5000,90d'c
M.,M,M) Failed in Base Metal
200-
Figure 11 shows results of the tensile
test at elevated temperatures between
200°C (392°F) and 600°C (1112°F) on Ti6A-4V joints brazed with Type 1510 filler
metal. The joint brazed at 900=C (1652°F)
for 5 min failed at the brazing interface in
a room-temperature test, but the tensile
strengths of 200=C (392°F) and 400°C
(752°F) are both equivalent to those of the
base metal. Though the joint strength at
600°C (1112°F) decreases considerably
and the fracture occurred at the brazing
interface, the reduction of area came up
to about 50° o , which is comparable to the
base metal value.
Fatigue Properties of Joints
10
Holding
Fig. 10—Relation
tensile properties
with Ti-Zr-Cu-Ni
20 30
(mm )
between
holding
time
and
of TI-6AI-4V joints
brazed
filler
metals.
Base Metal : T i - 6 A l - 4 V
Brazing Temperature : 900"c
Filler Metal : Type 1510
;i200
:
Time
1000
: 800
\ 600
i
;
400
O—O
900C,5min
I
£C—TM 900°C, 1 min
; 200-
•
. *
R.T
Failed in Base Metal
200
Test
400
Temperature
Fig. 11 —Elevated temperature
ties of TF6AI-4V joints brazed
filler
metal.
.900
•850
600
(°C )
tensile
properwith Type 1510
Fatigue tests were conducted under a
tension-tension mode with a stress cycle
of 3000 cpm and a stress ratio of 0.1. Figure 12 shows the results for Ti-6Al-4V
base metal exposed at 900°C (1652°F) for
10 min, and the joints brazed with Type
1510 filler metal at temperatures between
900°C (1652°F) and 1000°C (1832°F).
The data on the base metal are almost the
same as that in the literature (Ref. 16),
which indicates that the thermal cycle
does not deteriorate the fatigue properties.
Though all joints exhibited shorter lives
than those of the base metals, both joints
brazed at 900°C (1652°F) for 10 min and
at 950°C (1742°F) for 5 min below /? transus of the base metal exhibited sufficient
fatigue lives over 107 cycles at a maximum
stress of 590 MPa (85.5 ksi), where fatigue
limit is considered to be higher than the
strength of 107 cycles. However, fracture
of the joints occurred at the brazing interface in any case. Figure 13A shows a frac-
Base Metal: TJ-6AI-2.V
Filler Metal: Type 1510
•
O
• 900°C, 10min (Base Metal)
o 900°C,10min (Joint )
n
A
• 950°C, 5 m i n ( J o i n t )
A 1000°C, 5 m i n ( J o i n t )
tography of a fatigued joint brazed at
900°C (1652°F), where the cracks propagated irregularly along the acicular structure in the brazed zone.
On the other hand, the joints brazed at
1000°C (1832°F) above /3 transus temperature of TJ-6AI-4V alloy exhibit the fatigue
life of 1.8 X 106 cycles at a maximum
stress of 490 MPa (71 ksi), which is considerably inferior to those of the joints
made at 900°C (1652°F) and 950°C
(1742°F). As shown in Fig. 13B, the "fish
eye," which characterizes brittle fracture,
appeared on fracture surfaces of all the
joints brazed at 1000°C (1832°F).
The results indicate that the fatigue
properties of the joints made particularly
at 900°C (1652°F) are somewhat comparable to that of Ti-6AI-4V base metal at a
maximum stress below 590 MPa (85.5 ksi).
Corrosion Properties of Joints
After immersing joints in 5% NaCI solution at 35°C (95°F), observation of the
structure and tensile test were conducted
to determine the corrosion properties of
the joints. Joints made by using a silverbased alloy of Ag-28Cu-0.2Li were also
tested to compare with the developed
filler metals. The observation of structures
revealed that the CPTi joint brazed with
Ag-28Cu-0.2Li filler metal had such poor
corrosion resistance, that general corrosion had occurred at the interface between the base metal and the brazed
zone after immersing for only 72 h. On the
other hand, after immersing for 1000 h, no
corrosion structure was observed in any
CPTI and Ti-6AI-4V joints. These results
800
450
2X104
IC?
107
IC*
Cycle to Failure
Fig. 12-Fatigue
properties
of TI-6AI-4V
466-s | DECEMBER 1990
joints
brazed
with
(N)
Type
1510 filler
metal
Fig. 13 — Fractography
of fatigue fractured
surfaces of V-6AI-4V joints. A -brazedat
900°C
(1652°F); B-brazedat
1000'C
(1832°F).
demonstrate that these brazed joints have
sufficient corrosion resistance for salt solution.
Summary and Conclusions
The brazeability of the developed TiZr-Cu-Ti amorphous filler metals for CPTi
and Ti-6AI-4V alloy was investigated. The
conclusions are summarized as follows:
1) Ti-Zr-Cu-Ni amorphous filler metals
with melting points approximately 100°C
(180°F) lower than that of conventional
Ti-based filler metal (Ti-Cu-Ni LBFM, i.e.,
laminated brazing filler metal) can be
made.
2) The use of these filler metals makes
it possible to braze at below a-$ transformation and /3 transus temperatures of
CPTi and Ti-6AI-4V alloys, respectively. As
a result, joints having sufficient tensile
properties, as compared to those of the
base metals, can only be made by holding
for a short time at the brazing temperature.
3) In the case of brazing CPTi and
Ti-6AI-4V alloy at below a-{3 transformation and (8 transus temperature of each
base metal, the original structures of the
base metals are completely preserved,
and the brazed regions are distinct. O n
the contrary, in brazing above these temperatures, the grains of the base metals
are coarsened, and the brazed regions
consist of fine Widmanstatten structures,
sometimes beyond 150 ,um in width. Particularly in Ti-6AI-4V joints, a remarkable
decrease in ductility is caused by the
brazing thermal cycle.
4) The fatigue properties of Ti-6AI-4V
alloy joints brazed at 900°C (1652°F) for
10 min and 950°C (1742°F) for 5 min approach that of the base metal at maximum
stresses below 590 MPa (85.5 ksi). Brazing
at 1000°C (1832°F) above /? transus temperature, the joints exhibit less favorable
fatigue properties.
5) These brazed joints have sufficient
corrosion behavior so that no reduction in
tensile strength occurred after immersion
in a 5% NaCI solution for 1000 h.
A ckno wledgments
The authors wish to express their gratitude to Daido Steel Co. Ltd. for providing
the titanium and its alloy used in this
investigation. Financial support from the
Ministry of Education, Science and Culture
as grant-in-aid for developmental scientific research is also gratefully acknowledged.
References
1. Heberard, X., et al 1980. tow-temperature brazing (680°C) to Ti-6%AI-4%V titanium
alloy. Titanium 80(4):2415-2422.
2. Wada, T. 1966. The brazing of titanium.
Report of National Research Institute for Metals 9(6):78-87 (in lapanese).
3. Kaarlela, W. T., and Margolis, W. S. 1974.
Development of the Ag-AI-Mn brazing filler
metal for titanium. Welding journal 53(10):
629-636.
4. Howden, D. C , and Monroe, R. W. 1972.
Suitable alloys for brazing titanium heat exchangers. Welding journal 51(1):31-36.
5. tan, S. W „ 1982. faminated brazing filler
metals from titanium assemblies. Welding Journal61(10):23-38.
6. Fox, C. W., ef al. 1963. Development of
alloy for brazing columbium. Welding journal
42(12):535-s to 540-s.
7. Wada, T. 1967. The brazing of titanium.
Titanium Zirconium 15(5): 120-123 (in lapanese).
8. Kawamura, H. T. 1974. Brazing and lowpressure diffusion bonding of titanium alloys.
Mitsubishi Juko Giho 11(2):189-193 (in Japanese).
9. Elrod, S. D. 1981. Service Evaluation of
Aluminum-Brazed Titanium (ABTi). NASA Contractor Report 3418 (NASI-13681):1-41.
10. Royster, D. M., etal. 1982. Superplastic
forming/weld brazing of titanium skin-stiffened
compression panels. Proceedings of 27th National SAMPE Symposium: 569-582.
11. Well, R. R. 1975. Low-temperature largearea brazing of damage tolerant titanium structures. Welding lournal 54(10):348-s to
356-s.
12. Perun, K. R. 1967. Diffusion welding and
brazing of titanium 6AI-4V process development. Welding lournal 46(9):385-s to 390-s.
13. Freedman, A. H. 1971. Basic properties
of thin-film diffusion-brazed joints in TF6AI-4V.
Welding lournal 50(8):343-s to 356-s.
14. Well, R. R. 1976. Microstructural control
of thin-film diffusion-brazed titanium. Welding
journal 55{l):20-i to 27-s.
15. Hansen, M. 1958. Constitution of Binary
Alloys. New York, McGraw-Hill, pp. 1240 and
1244.
16. Sitsuhara, H. D. 1972. High-cycle fatigue
properties of titanium alloy. Titanium Zirconium
20(4):189-193 (in lapanese).
WRC Bulletin 343
May 1989
Destructive Examination of PVRC Weld Specimens 202, 203 and 251J
This Bulletin contains t h r e e reports:
( 1 ) Destructive Examination of PVRC Specimen 202 Weld Flaws by JPVRC
By Y. Saiga
( 2 ) Destructive Examination of PVRC Nozzle Weld Specimen 203 Weld Flaws by JPVRC
By Y. Saiga
( 3 ) Destructive Examination of PVRC Specimen 251J Weld Flaws
By S. Yukawa
The sectioning and examination of Specimens 202 and 203 were sponsored by the Nondestructive
Examination C o m m i t t e e of the Japan Pressure Vessel Research Council. The destructive examination of
Specimen 251J was performed at the General Electric Company in Schenectady, N.Y., under the
sponsorship of the Subcommittee on Nondestructive Examination of Pressure Components of the
Pressure Vessel Research C o m m i t t e e of the Welding Research Council. The price of WRC Bulletin 343 is
$24.00 per copy, plus $5.00 for U.S., or $8.00 for overseas, postage and handling. Orders should be sent
with payment to the Welding Research Council, Room 1 3 0 1 , 345 E. 4 7 t h St., New York, NY 10017.
WELDING RESEARCH SUPPLEMENT 1467-s