International Journal of Engineering Innovation & Research
Volume 5, Issue 4, ISSN: 2277 – 5668

Tensile Strength of Ti/Mg Alloys Dissimilar Bonding
Material Fabricated by Spark Plasma Sintering
Patchara Pripanapong1,*, Junko Umeda2, Hisashi Imai2, Makoto Takahashi2, Katsuyoshi Kondoh2
Abstract – Dissimilar metal joining between titanium andmagnesium alloys was performed by spark plasma sintering.
Metallurgical bonding between pure titanium andmagnesium alloys was successfully achieved by diffusion of
Al atom from magnesium alloy side to titanium andformation of Ti3Al intermetallic layer. A solution treatment
on magnesium alloys before bonding resulted in an increasedof Al content in Mg matrix, and improved tensile strength ofbonding material. Bonding pressure of 10 MPa was sufficient
to obtain a perfect contact between titanium and magnesium
alloys surface. A good bonding strength was obtained when
applying bonding time for 1 and 2 hr. Increasing of bonding
temperature facilitated a formation of nano-level Ti3Al
intermetallic layer resulted in improvement of bonding
strength. The highest bonding strength of 194±15 MPa was
obtained in Ti/AZ91 (ST) bonded at 475 ºC for 1 hr, which
representing 96.3% joint efficiency relative to the magnesium
alloy parent metal.
Keywords – Solid State Bonding, Spark Plasma Sintering,Ti/Mg Alloysdissimilar Material, Ti3Al Intermetallic Layer.

I. INTRODUCTION
Ti was became an interesting structural material
nowadays because it possess low density (4.51 g/cm3) withhigh specific strength, high strength at elevatedtemperature, good fatigue resistance, high corrosion
resistance and good biocompatibility. The main
application of Ti and its alloys were automobile andaerospace component such as engine parts of racing carthat high output, fast rotation and high response wererequired [1]-[2]. Moreover, Ti and its alloys were also
used in intake and exhaust valve in a conventional car byreplacing with high strength steel to reduce a weight ofcomponent. In the field of aerospace, Ti was mostly usedin airframe and turbo fan engine to reduce a weight ofaircraft and fuel consumption [3]-[4].
Furthermore, good biocompatibility of Ti made it
suitable to use in human body such as bone joint,
prosthesis bone or teeth. To further reduce a weight ofautomobile or aerospace component, many researchers
have been tried to bond Ti or its alloys with Al alloys. Y.
Li et al. studied on bonding between pure Ti and 6061-T6
aluminum alloy by electromagnetic stirring (EMS)
method. The electromagnetic stirring promotes the rotationof molten metal, resultedin the enlargement of bonding
diameter and formation of fine spheroid grain then highshear strength was obtained [5]. M. Samavatian et al.
studied onbonding between Ti64 and Al2024 (Al alloy)
with Cu-Zn interlayer by transient liquid phase (TLP)
bonding method. These materials were successfully
bonded by solid-state diffusion of Cu and Zn into Ti64 andAl2024 followed by eutectic formation and isothermal
solidification along the Cu-Zn/Al2024 interface [6].

Magnesium as the lightest structural material has been
applied to bond with various materials such as Al [7]-[8],Fe [9] and Cu [10] in order to reduce a weight ofcomponent used in structural application.
Bonding Ti to Mg alloys was an effective way to further
improve a weight saving compared to Al and its alloys.
However, bonding Ti to Mg alloys was a challenge work
because a large differences in physical properties such as
melting temperature and thermal expansion. Moreover,there is no intermetallic compound exists between themreferred to binary phase diagram [11]. The report related
to bonding between Ti and Mg alloys was still scarcerecently. Transient liquid phase bonding between AZ31
(Mg alloy) and Ti64 was reported by A.M. Atieh et al.
However, a pure Ni coated on Ti64 surface was necessary
to obtain a successfully bonded, and a thick intermetallic
compound (IMC) layer that degraded shear strength ofbonding material was formed due to eutectic liquid phaseformation during bonding [12]. Y. Fouadet al. studied thebonding between pure Ti and AZ31 with Al inserted sheet
fabricated by hot isostatic pressing (HIP), andsubsequently annealed. However, bonding component
showed a poor tensile strength due to a formation of thickintermetallic layer of 10 µm at the Al/AZ31 interface [13].
C. Tan et al. bonded a Ti64 and AZ31 together with AZ31
or AZ91 filler metal by laser welding method. Ti64/AZ31
bonded with AZ91 filler metal showed a formation of
Ti3Al reaction layer at bonding interface with a thicknessof 0.5 µm, and exhibited higher tensile-shear strengthcompared to joint component which applied AZ31 as afiller metal. Metallurgical bonding of Mg and Ti wasachieved by diffusion of Al atom to Ti side and formationof interaction layer between them [14]. To control athickness of IMCs layer within nano-level, solid-statebonding by spark plasma sintering (SPS) method that hightemperature and pressure could simultaneously introduced
to sample was an interesting solution to fabricate a highstrength Ti/Mg alloys dissimilar bonding material.
There are many reports proposed about an advantage of
SPS method in solid-state bonding between similar or
dissimilar materials such as short processing time anddefect-free bonding interface resulted in high bonding
strength compared to hot pressing [15]-[16]. In this work,
Al element in Mg alloy was selected as the intermediate
element to bond with Ti. The effect of solution treatment
on Mg alloy before bonding on tensile strength was
discussed. Moreover, the effect of bonding parameterssuch as temperature, time and pressure on bonding
interface characteristic and tensile strength was also
discussed.

Copyright © 2016 IJEIR, All right reserved
253International Journal
urnal of Engineering Innovation & Research
Volume 5,, Issue 4, ISSN: 2277 – 5668

II. EXPERIMENTAL PROCEDURE
Pure Ti rod (16 mm in diameter) with purity of 99.95%
and four types of cast Mg alloys such as AZ31B, AZ61,
AZ80, and AZ91 were used in this research, and allmaterials were purchased from Nilaco Co. Ltd. The pure
Ti contains H: 0.013, O: 0.13, N: 0.05, Fe: 0.3 in wt%, anda chemical composition of Mg alloys were shownshow in table
1. The Mg alloy ingot was machined to rod shape with 16
mm in diameter after that Ti and Mg alloys rod were cut
into 20 mm in length. Another batch of Mg alloys was
solution treated at 420 ºC
C for 12 hr and subsequently
quenched in water, this batch
tch will be named as Mg alloys(ST). The surface of parent metal was prepared before
bonding by grinding and polishing. The surface of Ti was
ground with SiC paper until 2000#, and polished with 0.3
and 0.05 µm Al2O3 colloidal, respectively. The surface of
Mg alloys were ground with SiC paper until 2000#, andpolished with 0.25 µm
m diamond paste. The surface
roughness of both Ti and Mg alloy were measured after
polishing by roughness testing machine (ACCRETECHSURFCOM1400G) from 5 positions. The microstructure
microstructu
of Ti, Mg alloys and Mg alloys (ST) was observed by
optical microscope and scanning electron microscope(JEOL JSM6500F).
). For bonding stage, parent metals wereinserted in carbon container and carbon punches wereplaced at both end of sample. Fig. 1a showsshoa schematic
drawing of component setting in SPS chamber, a tip ofthermocouple was 1 mm away from sample then atemperature was precisely measured during SPS. The
samples were bonded at 400, 420, 450 and 475 ºC with aheating rate of 15 ºC/min for 0.5, 1 and 2 hr, and abonding pressure was selected at 10 and 40 MPa. The
atmosphere in SPS chamber was controlled in vacuum,
and bonding sample was cooled in chamber after heatingstage.Fig. 1b shows a successfully bonded material
between Ti and Mg alloys by SPS. After bonding, samples
were cut at bonding interface for microstructure
observation that performed by scanning electron
microscope and transmission electron microscope (JEOL
JEM-2010).
). The surface of sample for microstructure
observation was prepared by the same method as Mg
alloys surface preparation, and etched by picric acid. For
TEM observation, a sample was prepared by focus ion
beam (FIB) equipment (HITACHI FB-2000A)
2000A) that sample
was sputtered until its thickness became lower than 100
nm. Three of tensile specimens were machined frombonding sample with a gauge length and diameter of 20
and 3 mm, respectively. Tensile test was performed atroom temperature under testing speed of 0.05
0mm/min.
Table I. Chemical compositions of Mg alloys used in thisresearch (wt%).
Mg alloys
Mg
Al
Zn
Mn
AZ31B
Bal.
2.8
0.8
0.3
AZ61
Bal.
5.5
0.7
0.3
AZ80
Bal.
7.8
0.3
0.4
AZ91
Bal.
8.5
0.6
0.4

Fig. 1. Schematic drawing of component setting in SPS
chamber a), and b) Bonded sample

III. RESULTS AND
ND DISCUSSION
A. Microstructure of Parent Metals
Microstructure of pure Ti composed of α-Ti matrix
without other phase with an approximate grain size of 30µm. Fig. 2 shows a microstructure of Mg alloys (AZ31B,
AZ61, AZ80, and AZ91) before and after solution
treatment used in this research. The β-Mg (Mg17Al12)
particles were observed on α-Mgmatrix
Mgmatrix in all Mg alloys,
which they commonly located at grain boundary, andsomeome of them were observed inside grain. The amount ofβ-Mg particle was depended on an Al content in Mg alloys
that amount of β-Mg particle was increased by increasingof Al content in Mg alloys (fig. a-1
a to d-1). Fig. a-2 to d-2
shows a microstructure of Mg alloys after solution treatedat 420 ºC for 12 hr, and subsequently quenched by water.
All of β-Mg particles were dissolved into α-Mgmatrix
after long time solution treated for all samples. The final
microstructure shows only α-Mgmatrix with anapproximate
ate grain size of 100 µm. The Al distribution
after solution-treatedtreated was much uniform compared tobefore solution-treated.
Fig. 3 shows Al content measured on grain boundary
and inside grain of Mg alloys and Mg alloys (ST) after
bonded to Ti by SEM-EDS.
EDS. ForFo AZ31B and other Mg
alloys, the difference in Al content between inside grain
and grain boundary was 2.5 and over 4.5 wt% (fig. 3a),respectively. The different in Al content measured from
two areas on Mg alloys matrix was high because Al tended
to segregate
ate at grain boundary and formed β-Mg particle
while it was depleted at inside grain after casting. After
solution-treated,
treated, the different in Al content measured from
two areas on AZ31B (ST) and other Mg alloys (ST) was
only 1 and not over 2.5 wt% (fig. 3b),3b) respectively. This
mean that the solution treatment was an effective method
to improve a uniformity of Al distribution since this madeall β-Mg particles dissolved into a matrix, and Al atom
was diffused from grain boundary (high Al content area)
to insidede grain (low Al content area).

B. Microstructure Analysis on Bonding Interface
The bonding interface of Ti/Mg alloys and Ti/Mg alloys(ST) observed by SEM was shown in fig. 4, which no
crack, void or other contaminations were existed at thebonding interface for all bonding samples. High applying
pressure cooperated with a good plastic
plast deformation of
Mg alloy resulted in a perfect contact between Ti and Mg

Copyright © 2016
201 IJEIR, All right reserved
254

International Journal of Engineering Innovation & Research
Volume 5, Issue 4, ISSN: 2277 – 5668

alloy surface. The bonding interface of Ti/Mg alloys (ST)shows two types of contact area, Ti contact with Mg alloy
matrix and Ti contact with re-precipitate β-Mg (RP β-Mg).
The re-precipitate β-Mg was formed during a sample wascooled down in SPS chamber. The contact between Ti andRP β-Mg was found in some location, and an area contact
between them was small since RP β-Mg has a plate shape(fig. 4a). For Ti/Mg alloys dissimilar material, the contact
area between Ti and remained β-Mg (RE β-Mg) was
observed in some area (fig. 4b) of Ti bonded with high Al
content Mg alloy such as AZ80 and AZ91. This contact
area was not observed in Ti/Mg alloys (ST) because all ofβ-Mg particles were dissolved into Mg matrix after
solution treated.

dislocation density area was observed on Mg alloy side
(fig. 5c).

Fig. 3. The distribution of Al element measured on grainboundary and inside grain of a) Mg alloys, and b) Solution
treated Mg alloys after bonded to Ti

Fig. 4. The bonding interface of dissimilar material
between Ti and Mg alloy a) Ti/Mg alloys (ST) and b)
Ti/Mg alloys

Fig. 2. Microstructures of as-received Mg alloys (a-1)
AZ31B (b-1) AZ61 (c-1)AZ80 and (d-1) AZ91, andsolution treated Mg alloys (a-2) AZ31B (b-2) AZ61 (c-2)
AZ80 and (d-2) AZ91 observed by OM
Fig. 5 shows a TEM observation at the bonding
interface of Ti/AZ80 and Ti/AZ80 (ST) bonded at 400 ºC
for 1 hr under applying pressure of 40 MPa. Highdislocation density area which dislocation formed a
network-like colony was observed in some area near thebonding interface, this area was generated by highapplying pressure that cause a plastic deformation on Mg
alloy side [17]-[18]. RE β-Mg was also observed on thebonding interface of Ti bonded with high Al content Mg
alloy such as AZ80 and AZ91 (fig. 5a). The existence ofRE β-Mg was confirmed by diffraction pattern, and highmagnification observation shows a dislocation network
inside a particle that was also effect by applying pressure(fig. 5b). On the other hand, RE β-Mg was not observed inbonding sample between Ti and Mg alloys (ST), only highFig. 5. TEM observation on the bonding interface ofbonding materials bonded at 400ºC for 1 hr under applying
pressure of 40 MPa a) Ti/AZ80 b) β-Mg particle at thebonding interface of a), and c) Ti/AZ80 (ST)

From TEM observation, a good bonding interface
between Ti and Mg alloys without micro crack, void or
unsatisfied oxide layer was obtained. Fig. 6 shows TEMEDS analysis on the bonding interface of Ti/AZ31B and
Ti/AZ91 bonded at 400ºC for 1 hrunderapplying pressure
Copyright © 2016 IJEIR, All right reserved
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International Journal of Engineering Innovation & Research
Volume 5, Issue 4, ISSN: 2277 – 5668

of 40 MPa. For Ti/AZ31B, a non-uniform diffusion layerof Al with a thickness of 25 nm was observed on thebonding interface. The formation of thin and non-uniform
diffusion layer of Al was affected by low Al content in
AZ31B (fig. 6a). The mapping of oxygen element
confirmed that no oxide layer was remained at the bonding
interface after SPS in all samples. The oxide layer was
reported to obstruct a fresh surface contact during solidstate bonding, resulted in a poor bonding strength [19].
TEM-EDS analysis on Ti/AZ91 shows a large high Al
content area at RE β-Mg particle remained after SPS (fig.
6b). The uniform diffusion layer of Al with a thickness of
40 nm was observed on the bonding interface. The
uniform diffusion layer of Al with a similar thickness was
also observed in Ti/AZ80. Compare to Ti/AZ31B, Al
diffusion layer of Ti/AZ91 was more uniform, and a
thickness was increased from 25 to 40 nm because a highAl concentration in AZ91 matrix. The oxide layer at thebonding interface of Ti/AZ91 was not observed after SPS
similar to Ti/AZ31B, which confirmed that an oxide layer
was destroyed by applying pressure.
Fig. 6c and 6d show TEM-EDS analysis on the bonding
interface of Ti/AZ31B (ST) and Ti/AZ91 (ST) bonded at
400ºC for 1 hr, respectively. For Ti/AZ31B (ST), a
uniform diffusion layer of Al with a thickness of 43 nm
was observed. The thickness of Al diffusion layer wasincreased compared to Ti/AZ31B because an increasing of
Al content at inside grain after solution treatment (fig. 3).
The bonding interface of Ti/AZ91 (ST) was shown in fig.
6d which no RE β-Mg was observed, and a diffusion layerof Al with a thickness of 56 nm was observed. The Al
diffusion layer with a similar thickness was also observedin Ti/AZ80 (ST). This increment of thickness compared to
Ti/AZ91 was affected by an increasing of Al content at
inside grain similar to Ti/AZ31B (ST).

IMC layer was Ti3Al. This Ti3Al layer was also observedon the bonding interface of Ti/Mg alloys (ST) bonded bysame condition. Fig. 8 shows bonding interface of
Ti/AZ31B (ST) and Ti/AZ91 (ST) bonded at 475ºC for 1
hr. From a bright field (BF) image of Ti/AZ31B (ST), a
discrete layer of Ti3Al with a thickness of 30 nm wasobserved on the bonding interface (fig. 8a). At this hightemperature, a reaction between Ti and Al was easily
occurred compare to low bonding temperature of 400 ºC.
The existence of Ti3Al layer was confirmed by dark field(DF) image which Ti3Al became a bright layer in an image(fig. 8b). The continuous layer of Ti3Al was observed on
the bonding interface of Ti/AZ91 (ST), a high bonding
temperature and high Al content in Mg matrix (fig. 3b)
facilitated a formation of Ti3Al layer that was clearlyobserved in this sample (fig. 8c). The bright Ti3Al layer in
DF image with a thickness of 50 nm was observed in fig
8d. These results indicated that a high content of Al in Mg
matrix resulted in a formation of thick and uniform Ti3Al
layer.

Fig. 7. Bonding interface of various bonding materials
bonded at 400ºC for 1 hr under applying pressure of 40
MPa a) Ti/AZ31B, b) Ti/AZ61, c) Ti/AZ80, and d)
Ti/AZ91

Fig. 6. Aluminum mapping on the bonding interface of a)
Ti/AZ31B, b) Ti/AZ91, c) Ti/AZ31B (ST), and d)
Ti/AZ91 (ST) bonded at 400ºC for 1 hr by TEM-EDS
Fig. 7 shows bonding interface of various bonding
materials bonded at 400ºC for 1hrunderapplying pressureof 40 MPa. Bonding interface of Ti/AZ31B (fig.7a) and
Ti/AZ61 (fig. 7b) shows no existence of intermetallic
compound (IMC) layer. On the other hand, a short IMC
layer was observed on the bonding interface of Ti/AZ80(fig. 7c) and Ti/AZ91 (fig. 7d) since high Al content in Mg
matrix contributed a reaction between Ti and Al [20].
However, this IMC layer was barely observed because of
low bonding temperature that Ti and Al was difficult toreact. Diffraction pattern of IMC layer indicated that thisFig. 8. Bonding interface of Ti/AZ31 (ST) and Ti/AZ91(ST) bonded at 475ºC for 1 hr a) Ti/AZ31B (ST)_BF, b)
Ti/AZ31B (ST)_DF, c) Ti/AZ91 (ST)_BF, and d) Ti/AZ91(ST)_DF

Copyright © 2016 IJEIR, All right reserved
256International Journal of Engineering Innovation & Research
Volume 5, Issue 4, ISSN: 2277 – 5668

C. Tensile Strength of Bonding Material
Fig. 9 shows an effect of solution treatment in Mg alloys
and Al content on bonding strength of sample bonded at
400ºC for 1 hr under applying pressure of 40 MPa.
Bonding strength of Ti/Mg alloys (ST) was higher
compared to Ti/Mg alloys for all bonding samples. For Ti
bonded to AZ31B, solution treated of AZ31B resulted inincreasing of bonding strength from 101.8±25 to 129.8±13MPa, and three of tensile samples machined from
Ti/AZ31B (ST) exhibited a similar bonding strength,
which reduces a gap of error bar. A large increased inbonding strength of Ti/AZ31B (ST) was explained by anincreasing in thickness of Al diffusion layer from 25 to 43
nm (fig. 6a and 6c), and an improvement of Al distribution
on bonding surface after solution treatment (fig. 3). This
improvement in Al distribution also provided a uniformbonding strength obtained from three of tensile samples.
Similar to Ti/AZ31B (ST), bonding strength of Ti/AZ61(ST) was increased from 115.1±24 to 138.5±15MPa, and a
uniform bonding strength was also obtained. In the case of
Ti/AZ80 (ST) and Ti/AZ91 (ST), a small increment inbonding strength about 15 MPa was achieved with a small
increased in thickness of Al diffusion layer from 40 to 56
nm (fig. 6b and 6d). The uniform bonding strength was
also obtained from Ti bonded to AZ80 and AZ91 because
a good distribution of high Al content was readily obtained
without solution treatment. The small increment ofbonding strength was affect by solution treatment that
dissolved all brittle β-Mg particles into a matrix, andimprove a distribution of Al on bonding surface resulted ina small increased in thickness of Al diffusion layer.
Moreover, a continuous layer of Ti3Al was observed in Ti
bonded to AZ80 (ST) and AZ91 (ST) resulted in higher
bonding strength compared to Ti/AZ31B (ST) and
Ti/AZ61 (ST) which small layer of Ti3Al was observed.
The Ti3Al layer was formed by a reaction between
diffused Al and Ti at the bonding interface of Ti/AZ80(ST) and Ti/AZ91 (ST).

Fig. 9. Effect of solution treatment in Mg alloys and Al
content on bonding strength of sample bonded at 400ºC
for 1 hr under applying pressure of 40 MPa
Fig. 10 shows an effect of bonding time, bonding
pressure and bonding temperature on bonding strength of
Ti/Mg alloys (ST) dissimilar material. Fig. 10a shows abonding strength of Ti/Mg alloys (ST) bonded at 400ºCfor

various bonding times such as 0.5, 1 and 2 hr under
applying pressure of 40 MPa. Ti/Mg alloys (ST) bonded
for 0.5 hr shows a poor bonding strength, only Ti/AZ91(ST) exhibited a good bonding strength with a thickness of
Al diffusion layer of 42 nm. In the case of Ti/AZ31B (ST),all of tensile samples were broke during machining into
tensile sample. The thickness of Al diffusion layer was
decreased from 43 to 12 nm compared to sample bonded
at 1 and 2 hr (fig. 6c). Low Al content in AZ31B and ashort diffusion time of Al element resulted in poor
bonding strength of this bonding sample. This also
occurred in Ti/AZ61 (ST) that one of tensile sample wasbroke during machining. Ti/AZ80 (ST) bonded for 0.5 hralso exhibited a poor bonding strength of 130.6 MPa
compared to sample bonded for 1 and 2 hr. A particle ofTi3Al was observed on the bonding interface instead ofsmall layer because of short bonding time. These results
show that a short bonding time of 0.5 hr was not sufficientfor bonding between Ti and Mg alloys (ST) because a
non-complete reaction between Ti and Al element, and adecreasing in thickness of Al diffusion layer. The sample
bonded for 1 and 2 hr show a similar characteristic(Thickness of Al diffusion layer and a formation of Ti3Al)
at the bonding interface resulted in similar bonding
strength for all bonding materials. This result indicatedthat applying bonding time for 1 hr was sufficient for TiAl interaction and diffusion of Al element from Mg alloys
side to Ti surface. Consequently, a good bonding strength
between Ti and Mg alloys (ST) was obtained.
Fig. 10b shows an effect of bonding pressure on
bonding strength of Ti/Mg alloys (ST) bonded at 400ºC
for 1 hr under applying pressure of 10, 20, and 40 MPa.
The bonding strength obtained from these three bonding
conditions was rather similar, and none of bonding
samples fabricated by applying low pressure of 10 MPa
exhibited a poor bonding strength. This was explained bya good deformability of Mg alloy that a perfect contact
between Ti and Mg alloys surface was easily achieved
even at low bonding pressure [21]. The dislocation piledup area was increased on Mg alloys side for sample
bonded under 40 MPa compared to 10 and 20 MPa, but
this was not effect on a thickness of Al diffusion layer,
Ti3Al formation and bonding strength. Applying low
bonding pressure has an advantage that a cracking ofcarbon container was prevented when it was used formany times.
Fig. 10c shows a bonding strength of Ti/Mg alloys (ST)bonded at various temperatures for 1 hr under applying
pressure of 10 MPa. Bonding strength of Ti/AZ31B (ST)and Ti/AZ61B (ST) was gradually increased whenincreased a bonding temperature from 400 to 475ºC,
which bonding strength increased 15 and 27 MPa for
Ti/AZ31B (ST) and Ti/AZ61 (ST), respectively.
Moreover, a more uniform bonding strength was obtained
from three of tensile samples when bonding temperature
was over 420 ºC because high bonding temperaturefacilitated a reaction between Ti and Al element. This was
confirmed by a formation of discrete Ti3Al layer at thebonding interface of Ti/AZ31B (ST) at 475 ºC (fig. 8a).
The bonding strength of Ti/AZ80 (ST) and Ti/AZ91 (ST)Copyright © 2016 IJEIR, All right reserved257International Journal of Engineering Innovation & Research
Volume 5, Issue 4, ISSN: 2277 – 5668

bonded at 475 ºC was increased compared to sample
bonded at 400 ºC in a small value of 12 and 9 MPa,
respectively. The characteristic at the bonding interface of
Ti/AZ80 (ST) and Ti/AZ91 (ST) bonded at 420, 450, and475 ºC was rather similar which corresponded to theirbonding strength. However, a thick and continuous Ti3Al
layer with a thickness of 50 nm (fig. 8c) was easily
observed on the bonding interface of Ti/AZ80 (ST) and
Ti/AZ91 (ST) bonded at 475 ºC compared to 420 and 450ºC because of good reaction between Ti and Al at highbonding temperature. Ti/AZ91 (ST) bonded at 475 ºCshows the highest bonding strength among dissimilarmaterials of 193.4±8 MPa. Increasing of bonding
temperature was facilitated a Ti-Al reaction at the bonding
interface resulted in an improvement of bonding strength.

improvement of bonding strength by increasing in bonding
temperature (fig. 10c). In the case of Ti/AZ31B (ST) and
Ti/AZ61 (ST), bonding efficiency was large improved
when bonding temperature increased from 450 to 475 ºC
because a formation of small Ti3Al layer (fig. 8a).
Bonding efficiency of Ti/AZ80 (ST) and Ti/AZ91 (ST)
was also improved but in a small value compared to
Ti/AZ31B (ST) and Ti/AZ61 (ST) because no significant
changes at the bonding interface. The highest bonding
efficiency of 96.3% was obtained from Ti/AZ91 (ST)bonded at 475 ºC for 1 hr under applying pressure of 10
MPa. This sample shows an excellent bonding strengththat was closed to a tensile strength of AZ91 (ST) parent
metal.

Fig. 11. Effect of bonding temperature and Al content on
bonding efficiency of Ti/Mg alloys (ST) dissimilarmaterial bonded at 400, 420, 450, and 475 ºC for 1 hrunder applying pressure of 10 MPa

IV. CONCLUSION

Fig. 10. Effect of a) Bonding time, b) Bonding pressure,and c) Bonding temperature on bonding strength of Ti/Mg
alloys (ST) dissimilar material

Ti and Mg alloys were successfully bonded by applying
SPS which high temperature and pressure wassimultaneously introduced to sample. The diffusion of Al
element from Mg alloy side to the bonding interface andformation of Ti3Al intermetallic layer were considered abonding mechanism between Ti and Mg alloys. The
conclusion was written below.
1. Solution treated of Mg alloys provided a uniform
distribution of Al element, and increased Al content ina matrix resulted in uniform bonding strength andimprovement of it.
2. Mg alloy possessed high Al content exhibited a higher
bonding strength compared to Mg alloy possessed low
Al content when bonded to Ti. High Al content
provided a thick Al diffusion layer and facilitated aformation of Ti3Al layer at the bonding interface
resulted in increasing of bonding strength.
3. Variation of bonding pressure from 10 to 40 MPa had
no effect on bonding strength since a perfect contact
between Ti and Mg alloys was readily obtained under
applying pressure of 10 MPa. This was explained by agood deformability of Mg alloys at high temperature.
4. Applying bonding time for 1 hr was sufficient forbonding between Ti and Mg alloys because long
bonding time of 2 hr also gave a similar bonding

Fig. 11 shows a bonding efficiency of Ti/Mg alloys (ST)bonded at 400, 420, 450, and 475 ºC for 1 hr under
applying pressure of 10 MPa. The bonding efficiency was
simply calculated by (1).
Bonding efficiency = (σb/σp) ×100(1)When, σb= Bonding strength of bonding sample (MPa)σp = Tensile strength of parent Mg alloys (MPa)The result shows that a bonding efficiency of eachbonding material was gradually increased when bonding
temperature was increased. This result correlated with an
Copyright © 2016 IJEIR, All right reserved258International Journal
urnal of Engineering Innovation & Research
Volume 5,, Issue 4, ISSN: 2277 – 5668

5.

strength. Sample bonded for 0.5 hr exhibited poor
bonding strength (except for Ti/AZ91 (ST)) due to ashort Al diffusion time resulted in non-complete
nonreaction between Ti and Al in Mg alloy.
For Ti/AZ31B (ST) and Ti/AZ61 (ST), increasing ofbonding temperature from 400 to 475 ºC resulted in
an improvement of bonding strength by a formation of
Ti3All layer. Bonding strength of Ti/AZ80 (ST) and
Ti/AZ91 (ST) was little improved when bonding
temperature was increased from 400 to 475 ºC
because no significant changes in characteristic at thebonding interface.

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PatcharaPripanapongwas born in Bangkok, Thailand.
PatcharaPripanapong
He received both B.S. and M.S. degrees fromdepartment of Metallurgical engineering,
Chulalongkorn University, Thailand. Now, He is PhD
candidate of Osaka University. His major fields ofstudies are (1) Titanium
anium matrix composites fabricatedby powder metallurgy route (2) Joining of lightmaterials between Ti and Mg alloys. He published two
publications with impact factor.
Junko Umeda,, Engineering Doctor, is an assistantprofessor of Joining and Welding Research Institute,
Osaka University. She got her Engineering Doctor’s
degree at Osaka University in 2010. Her current
research involves the study on 1) Powder metallurgytitaniummaterials reinforced
einforced with ubiquitous lightelements，2)2) Advanced recycling of non-phagocytic
biomass.
Hisashi Imaiwas
was born in 27th July 1979. He receive
doctoral degree from Toyama University in engineering
field. He admitted to Joining and Welding ResearchInstitute (JWRI) in Osaka University as special
appointed researcherin 2007. He became a special
appointed lecturer and lecturer in JWRI in 2011 and2014, respectively.
Makoto Takahashi,
Takahashi He is Associate Professorin
Joining and Welding Research Institute, Osaka
University, Osaka. He received his D. Eng. degree inEngineering Science from Osaka University. His
Research Area: Analysis of microstructures of metals
and inorganic materials by transmission electron
microscopy, anodic bonding of oxide glass to
conductive materials, welding metallurgy.
metallurg He has more than 19years of
research and teaching experience. He has contributed more than 60
academic articles in various national and international journals.
Katsuyoshi Kondoh is a profess or of Osaka
University, Joining and Welding Research Institute(JWRI),JWRI), Japan, and also an adviser to President of
Osaka University. He received both B.S. and M.S.
degrees and PhD from Osaka University. His main
research topics are (1) Advanced metal matrix
composites reinforced un-bundledunnano carbon
materials, (2) Atomic
mic scale microstructure control ofmetals for ultra-highhigh strengthening, (3) Surface potential control for
improvement of galvanic corrosion phenomenon of light metals. He
published more than 220 academic papers with impact factor and got 170
and more patents.
nts. He also got Prime Minister Awards of Science andTechnology in 2014, and 26 awards from domestic and international
materials science societies.

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