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Transient liquid-phase bonding of T91 steel pipes using amorphous foil
Materials Science and Engineering A 499 (2009) 114–117
Contents lists available at ScienceDirect
Materials Science and Engineering A journal homepage: www.elsevier.com/locate/msea
Transient liquid-phase bonding of T91 steel pipes using amorphous foil S.J. Chen a,∗ , H.J. Tang b , X.T. Jing c a
School of Materials Science & Engineering, Henan Polytechnic University, Jiaozuo, Henan 454000, China School of Electrical Engineering & Automation, Henan Polytechnic University, Jiaozuo, Henan 454000, China c School of Materials Science & Engineering, Xi’an University of Technology, Xi’an, Shanxi 710048, China b
a r t i c l e
i n f o
Article history: Received 23 May 2007 Received in revised form 22 September 2007 Accepted 11 November 2007 Keywords: TLP bonding T91 steel Interlayer Microstrostructure Amorphous foil
a b s t r a c t T91 steel pipes were joined by the transient liquid-phase (TLP) bonding process using BNi2 , Fe78 Si9 B13 and FeNiCrSiB amorphous filler in argon atmosphere. The microstructures and properties, as well as the element distribution of TLP joints of T91 martensitic steel with different filler metals have been examined. The testing results showed that the tensile strength and bend strength at room temperature of the joint with Fe–Ni–Cr–Si–B amorphous filler were equal to greater than that of the substrate. In contrast, however, boride is found in the joint region bonded with Fe78 Si9 B13 interlayer. TLP bonding using the nickel-base foil BNi2 , resulted in a bond region stabilized by the high nickel concentration. It is considered that fracture of the joints is caused by these brittle intermetallics at the interface and the discontinuity of the bond line microstructure. © 2008 Elsevier B.V. All rights reserved.
1. Introduction Transient liquid-phase (TLP) bonding is a widely used capillary joining process [1,2]. The process and phenomenon of TLP bonding are very similar to those of conventional brazing. The most important difference between TLP bonding and brazing is the solidification behaviour of the liquid phase formed during bonding. In TLP diffusion bonding, a suitable interlayer containing a melting-point depressant (MPD) is inserted between pieces to be joined and inter-diffusion between interlayer and the base material leads to the formation of a low-melting-point liquid phase (e.g. eutectic) at the bonding temperature which is held constant. The solidified bond should consist of a primary solid solution with a composition similar to that of the parent metal and free from precipitates. One of the most important considerations for producing a sound joint will be its final composition, which will depend on the interlayer used [3,4]. Upon completion of the TLP bonding process, the re-melt temperature of the bond is similar to that of the base metal. This melting shift differentiates transient liquid-phase bonding from high-temperature brazing and makes it attractive for applications requiring elevated service temperatures. Nickel-base brazing materials were designed to suit nickel-base superalloys [5,6].
∗ Corresponding author. Tel.: +86 391 3983190; fax: +86 391 3987461. E-mail address: [email protected] (S.J. Chen). 0921-5093/$ – see front matter © 2008 Elsevier B.V. All rights reserved. doi:10.1016/j.msea.2007.11.133
The martensitic T91 steel is a readily available industrial material (stabilized with vanadium and niobium additions), which was qualified as steam generator material for non-nuclear and nuclear power plants. The modified 9Cr–1Mo steel T91 has higher strength, low thermal stress and lower ductile–brittle transition temperature (DBTT) shift after irradiation. Unfortunately, it is very difficult to fusion weld this kind of alloy as it is susceptible to hot cracking [4]. In this work, BNi2 , Fe78 Si9 B13 and FeNiCrSiB amorphous foil were selected as interlayer alloy for transient liquid-phase bonding of T91 steel pipes. The aim this study was to find or develop an interlayer based on Fe–Ni–Si–B system, which should be a suitable interlayer for TLP bonding the martensitic T91 steel. The joints produced have been characterized by metallographic examination and tensile tests at room temperature. 2. Materials and experimental procedures The chemical composition of martensitic T91 steel used in experiment is given as Table 1. The property and mechanical properties of the steel pipe are: 63.5 mm diameter, 4.6 mm wall thickness, tensile strength 585 b (MPa). The commercial metglass nickel-base brazing foils BNi2 (30-m thick), and the 30-m thick iron-base foil Fe78 Si9 B13 (produced for magnetic application) were supplied by market. FeNiCrSiB was produced to use for martensitic T91 transient liquid-phase bonding (40-m thick). The respective chemical compositions in weight percent and melting point for the interlayer are given in Table 2. The induction heat was
S.J. Chen et al. / Materials Science and Engineering A 499 (2009) 114–117
115
Table 1 Chemical compositions of T91 steel (wt.%)
T91
C
Si
Mn
P
S
Ni
Cr
Mo
V
Nb
N
Fe
0.08 – 0.12
0.20 – 0.50
0.30 – 0.60
≤0.02
≤0.01
≤0.4
8.00 – 9.50
0.85 – 1.05
0.18 – 0.25
0.06 – 0.10
0.06 – 0.07
Base
Table 2 Chemical compositions (wt.%) and melting point insert metal used Material
Ni
Cr
B
Si
Fe
Melting point (◦ C)
FeNiCrSiB Fe78 Si9 B13 BNi2
43–47
3.9
Base
6–8
7.4 13 2.75–3.5
6–8 9 4–5
Base Base 2.5–3.5
1080–1130 1150–1165 970–1000
Fe78 Si9 B13 was selected as the filler metal, the tensile strengths of joints is up to 736 MPa. The mechanical properties of TLP diffusion bonding joints of the T91 steel with FeNiCrSiB interlayer are best. The optimum process has been obtained with the result shown as follows: bond made at 1250 ◦ C for 3 min under 6 MPa with FeNiCrSiB composite interlayer. 3.2. Microstructure of the TLP joint
Fig. 1. Diagram of the T91 steel pipes sampling used to tensile and bend test.
used as the thermal resource. Bonded surfaces were ground flat by 800 grade emery paper, grinding paper and cleaned in ethanol and acetone prior to diffusion bonding. Transient liquid-phase bonding experiments were conducted in air and used argon as protective gas. The specimens were bonded at 1225 ◦ C for 3 min for isothermal solidification, and bonding pressure was 6 MPa. Interface microstructures were investigated by scanning electron microscopy (SEM). Composition analyses were also carried out using the energy dispersion X-ray (EDX) spectrum system of the corresponding SEM(JXA-8800R). The strength and bend test of TLP bonding joint were carried out with universal testing machine WES-600 at room temperature. The T91 TLP bonding joint were cut into 100 mm × 10 mm × 4.5 mm and 100 mm × 8 mm × 4.5 mm discs by milling for strength testing and bend testing. Fig. 1 shows the diagram of the T91 steel pipes bonding sampling used to tensile and three-point bend specimens. 3. Results and discussions 3.1. Strength of the TLP joint Table 3 shows the average room temperature mechanical properties of T91 joints bonding at 1225 ◦ C with different interlayers. The tensile strength of joints with BNi2 alloy foil is 358 MPa. When
Fig. 2(a) shows a back-scattered image of the T91 joint brazed at 1225 ◦ C for 3 min under 6 MPa with BNi2 interlayer. Interface of joint have a clear outline. Interspace of the T91 joint is white solid solution. Tensile strengths of the transient liquid-phase bonding joint was lower than T91 base steel. Fig. 2(b) is a back-scattered election image of the cross-section of the T91 joint bonded at 1225 ◦ C for 3 min under 6 MPa with Fe78 Si9 B13 interlayer. It can be found from the figure that there exist intermittently black lines at joint center. There were obvious reacting layer arose at the interface of joint. It can be determined that some boride was found at the interfaces of joint. Fig. 2(c) is a back-scattered electron image of the cross-section of the T91 joint bonded at 1225 ◦ C for 3 min under 6 MPa with FeNiCrSiB interlayer. The joint of bonded with FeNiCrSiB interlayer can be found free from precipitates, and with a composition and microstructure as similar as to that of the parent alloy. Fig. 2(d) is a corresponding image of the cross-section of the T91 joint bonded at 1250 ◦ C for 3 min under 6 MPa with FeNiCrSiB interlayer. The joint microstructure are quite similar to the parent alloy. 4. Discussion In metallurgical terms, a sound joint can be classified as one free from precipitates, free from porosity and with a composition and microstructure as similar as possible to that of the parent alloy. Both TLP bonding and conventional brazing have a liquid phase produced by eutectic reactions. If the active element is not one component of the eutectic liquid, the liquid phase will still remain after long dwell times at the bonding temperature, because the composition of the eutectic liquid cannot be
Table 3 The mechanical properties of TLP diffusion bonding joints of the T91 steel with different interlayer Interlayer
Temperature (◦ C)
BNi2 Fe78 Si9 B13
1225
FeNiCrSiB
1225 1250
Tensile strengths (MPa)
Bend strengths (MPa)
Break position
358 736 780 860
100 400 679 980
Joints Joints Base metal
116
S.J. Chen et al. / Materials Science and Engineering A 499 (2009) 114–117
Fig. 2. Back-scattered electron image and major element content distribution of T91 steel TLP bonding joints with different interlayers (bonding conditions: (a, b and c) 1225 ◦ C for 3 min and (d) 1250 ◦ C for 3 min).
obviously changed during bonding. The liquid solidifies gradually only when the temperature is decreased. Such a bonding process can be termed brazing. On the other hand, if the active element is involved in the eutectic reaction, such a bonding technique can be termed TLP bonding. It is obvious that with the progress of
the interface reaction between active element and parent material, the composition of the eutectic liquid phase will be changed, and the melting point of the eutectic alloy will be increased along the liquidus and the liquid phase will solidify at the bonding temperature.
S.J. Chen et al. / Materials Science and Engineering A 499 (2009) 114–117
The interface reaction is complicated and there are many factors to ascribe to the reaction including bonding pressure, temperature, dwell time, surface condition of the mating surface, heat treatment status of the parent materials, ambient gas, etc. In the present study, the main thermodynamic factors, i.e. bonding pressure, bonding temperature and dwell time at elevated temperature, were investigated in detail to clarify the interface reaction and interface evolution during bonding. Because the diffusion of MPD into the parent materials is the controlling factor for TLP bonding, all parameters concerned with the diffusion process of MPD will contribute to the TLP bonding process. Based on the characteristics of the TLP bonding process, the bonding temperature should be high enough so that the liquid phase is stable and the diffusion driving force of MPD atoms is high enough to overcome the obstacle of diffusion potential. Generally speaking, the bonding temperature employed in TLP bonding process should meet the following conditions: (1) it should be high enough so that the interlayer is fully or partially in the liquid state; (2) in order to shorten the dwell time which is needed for the isothermal solidification of the liquid phase, any undesirable intermetallics should be avoided so that MPD atoms can have a high diffusion coefficient; 1250 ◦ C has been chosen as the lowest bonding temperature in the present study. Fig. 1 shows the morphology of the joint produced at 1250 ◦ C. Compared with 1225 ◦ C used FeNiCrSiB interlayer, some differences can clearly be seen: 1250 ◦ C process has been significantly strengthened by the increase in temperature, there is no continuous white strip in the interlayer. Dwell time is also very important for TLP bonding. Dwell time at bonding temperature must be long enough so that a liquid region with sufficient thickness will be formed and flow to fill any voids formed at the interface. As shown above, obtaining a sound interface TLP-bond between interlayer and T91 is a decisive process in manufacturing a defectfree joint of T91. So it is important to investigate the joint formation process in order to optimize the experimental parameters and obtain a good understanding of the bonding process [7].
117
5. Conclusions Based on the experimental results and discussion, the following conclusions can be drawn: (i) A novel interlayer based on the ternary FeNiCrSiB system is found to be a suitable interlayer for TLP bonding giving T91 steel. No bonding defects have been observed at the interface where the T91 joint bonded at 1250 ◦ C for 3 min under 6 MPa with FeNiCrSiB interlayer. (ii) TLP bonding using the Fe78 Si9 B13 interlayer produces nearparent metal properties, however, the high concentrations of boron present in the vicinity of the joint appear to have an embrittling effect. (iii) TLP bonding using the nickel-base amorphous foil BNi2 , resulted in a bond region stabilized by the high nickel concentration. The high concentration of nickel present in the core of the joint was found to reduce the joint strengths. Acknowledgements The authors would like to thank Shandong Electric Power College of China for financial supports. They also wish to acknowledge Professor X.G. Li in the Shandong Electric Power College (Jinan, China) for supporting the research. References [1] [2] [3] [4] [5] [6] [7]
W.F. Gale, D.A. Butts, Sci. Tech. Weld. Join. 9 (2004) 283–300. H. Duan, M. Kocak, K.H. Bohm, V. Ventzke, Sci. Tech. Weld. Join. 9 (2004) 513–518. G. Cam, M. Kocak, Int. Mater. Rev. 43 (1998) 1–30. T.I. Khan, E.R. Wallach, J. Mater. Sci. 30 (1995) 5151–5160. Y.N. Liang, M.I. Osendi, P. Miranzo, J. Eur. Ceram. Soc. 23 (2003) 547–553. E. Lugscheider, T. Cosack, Weld. Res. 10 (1998) 215–221. S.J. Chen, X.T. Jing, X.G. Li, Trans. Chin. Weld. Inst. 25 (2004) 73–76.
Contents lists available at ScienceDirect
Materials Science and Engineering A journal homepage: www.elsevier.com/locate/msea
Transient liquid-phase bonding of T91 steel pipes using amorphous foil S.J. Chen a,∗ , H.J. Tang b , X.T. Jing c a
School of Materials Science & Engineering, Henan Polytechnic University, Jiaozuo, Henan 454000, China School of Electrical Engineering & Automation, Henan Polytechnic University, Jiaozuo, Henan 454000, China c School of Materials Science & Engineering, Xi’an University of Technology, Xi’an, Shanxi 710048, China b
a r t i c l e
i n f o
Article history: Received 23 May 2007 Received in revised form 22 September 2007 Accepted 11 November 2007 Keywords: TLP bonding T91 steel Interlayer Microstrostructure Amorphous foil
a b s t r a c t T91 steel pipes were joined by the transient liquid-phase (TLP) bonding process using BNi2 , Fe78 Si9 B13 and FeNiCrSiB amorphous filler in argon atmosphere. The microstructures and properties, as well as the element distribution of TLP joints of T91 martensitic steel with different filler metals have been examined. The testing results showed that the tensile strength and bend strength at room temperature of the joint with Fe–Ni–Cr–Si–B amorphous filler were equal to greater than that of the substrate. In contrast, however, boride is found in the joint region bonded with Fe78 Si9 B13 interlayer. TLP bonding using the nickel-base foil BNi2 , resulted in a bond region stabilized by the high nickel concentration. It is considered that fracture of the joints is caused by these brittle intermetallics at the interface and the discontinuity of the bond line microstructure. © 2008 Elsevier B.V. All rights reserved.
1. Introduction Transient liquid-phase (TLP) bonding is a widely used capillary joining process [1,2]. The process and phenomenon of TLP bonding are very similar to those of conventional brazing. The most important difference between TLP bonding and brazing is the solidification behaviour of the liquid phase formed during bonding. In TLP diffusion bonding, a suitable interlayer containing a melting-point depressant (MPD) is inserted between pieces to be joined and inter-diffusion between interlayer and the base material leads to the formation of a low-melting-point liquid phase (e.g. eutectic) at the bonding temperature which is held constant. The solidified bond should consist of a primary solid solution with a composition similar to that of the parent metal and free from precipitates. One of the most important considerations for producing a sound joint will be its final composition, which will depend on the interlayer used [3,4]. Upon completion of the TLP bonding process, the re-melt temperature of the bond is similar to that of the base metal. This melting shift differentiates transient liquid-phase bonding from high-temperature brazing and makes it attractive for applications requiring elevated service temperatures. Nickel-base brazing materials were designed to suit nickel-base superalloys [5,6].
∗ Corresponding author. Tel.: +86 391 3983190; fax: +86 391 3987461. E-mail address: [email protected] (S.J. Chen). 0921-5093/$ – see front matter © 2008 Elsevier B.V. All rights reserved. doi:10.1016/j.msea.2007.11.133
The martensitic T91 steel is a readily available industrial material (stabilized with vanadium and niobium additions), which was qualified as steam generator material for non-nuclear and nuclear power plants. The modified 9Cr–1Mo steel T91 has higher strength, low thermal stress and lower ductile–brittle transition temperature (DBTT) shift after irradiation. Unfortunately, it is very difficult to fusion weld this kind of alloy as it is susceptible to hot cracking [4]. In this work, BNi2 , Fe78 Si9 B13 and FeNiCrSiB amorphous foil were selected as interlayer alloy for transient liquid-phase bonding of T91 steel pipes. The aim this study was to find or develop an interlayer based on Fe–Ni–Si–B system, which should be a suitable interlayer for TLP bonding the martensitic T91 steel. The joints produced have been characterized by metallographic examination and tensile tests at room temperature. 2. Materials and experimental procedures The chemical composition of martensitic T91 steel used in experiment is given as Table 1. The property and mechanical properties of the steel pipe are: 63.5 mm diameter, 4.6 mm wall thickness, tensile strength 585 b (MPa). The commercial metglass nickel-base brazing foils BNi2 (30-m thick), and the 30-m thick iron-base foil Fe78 Si9 B13 (produced for magnetic application) were supplied by market. FeNiCrSiB was produced to use for martensitic T91 transient liquid-phase bonding (40-m thick). The respective chemical compositions in weight percent and melting point for the interlayer are given in Table 2. The induction heat was
S.J. Chen et al. / Materials Science and Engineering A 499 (2009) 114–117
115
Table 1 Chemical compositions of T91 steel (wt.%)
T91
C
Si
Mn
P
S
Ni
Cr
Mo
V
Nb
N
Fe
0.08 – 0.12
0.20 – 0.50
0.30 – 0.60
≤0.02
≤0.01
≤0.4
8.00 – 9.50
0.85 – 1.05
0.18 – 0.25
0.06 – 0.10
0.06 – 0.07
Base
Table 2 Chemical compositions (wt.%) and melting point insert metal used Material
Ni
Cr
B
Si
Fe
Melting point (◦ C)
FeNiCrSiB Fe78 Si9 B13 BNi2
43–47
3.9
Base
6–8
7.4 13 2.75–3.5
6–8 9 4–5
Base Base 2.5–3.5
1080–1130 1150–1165 970–1000
Fe78 Si9 B13 was selected as the filler metal, the tensile strengths of joints is up to 736 MPa. The mechanical properties of TLP diffusion bonding joints of the T91 steel with FeNiCrSiB interlayer are best. The optimum process has been obtained with the result shown as follows: bond made at 1250 ◦ C for 3 min under 6 MPa with FeNiCrSiB composite interlayer. 3.2. Microstructure of the TLP joint
Fig. 1. Diagram of the T91 steel pipes sampling used to tensile and bend test.
used as the thermal resource. Bonded surfaces were ground flat by 800 grade emery paper, grinding paper and cleaned in ethanol and acetone prior to diffusion bonding. Transient liquid-phase bonding experiments were conducted in air and used argon as protective gas. The specimens were bonded at 1225 ◦ C for 3 min for isothermal solidification, and bonding pressure was 6 MPa. Interface microstructures were investigated by scanning electron microscopy (SEM). Composition analyses were also carried out using the energy dispersion X-ray (EDX) spectrum system of the corresponding SEM(JXA-8800R). The strength and bend test of TLP bonding joint were carried out with universal testing machine WES-600 at room temperature. The T91 TLP bonding joint were cut into 100 mm × 10 mm × 4.5 mm and 100 mm × 8 mm × 4.5 mm discs by milling for strength testing and bend testing. Fig. 1 shows the diagram of the T91 steel pipes bonding sampling used to tensile and three-point bend specimens. 3. Results and discussions 3.1. Strength of the TLP joint Table 3 shows the average room temperature mechanical properties of T91 joints bonding at 1225 ◦ C with different interlayers. The tensile strength of joints with BNi2 alloy foil is 358 MPa. When
Fig. 2(a) shows a back-scattered image of the T91 joint brazed at 1225 ◦ C for 3 min under 6 MPa with BNi2 interlayer. Interface of joint have a clear outline. Interspace of the T91 joint is white solid solution. Tensile strengths of the transient liquid-phase bonding joint was lower than T91 base steel. Fig. 2(b) is a back-scattered election image of the cross-section of the T91 joint bonded at 1225 ◦ C for 3 min under 6 MPa with Fe78 Si9 B13 interlayer. It can be found from the figure that there exist intermittently black lines at joint center. There were obvious reacting layer arose at the interface of joint. It can be determined that some boride was found at the interfaces of joint. Fig. 2(c) is a back-scattered electron image of the cross-section of the T91 joint bonded at 1225 ◦ C for 3 min under 6 MPa with FeNiCrSiB interlayer. The joint of bonded with FeNiCrSiB interlayer can be found free from precipitates, and with a composition and microstructure as similar as to that of the parent alloy. Fig. 2(d) is a corresponding image of the cross-section of the T91 joint bonded at 1250 ◦ C for 3 min under 6 MPa with FeNiCrSiB interlayer. The joint microstructure are quite similar to the parent alloy. 4. Discussion In metallurgical terms, a sound joint can be classified as one free from precipitates, free from porosity and with a composition and microstructure as similar as possible to that of the parent alloy. Both TLP bonding and conventional brazing have a liquid phase produced by eutectic reactions. If the active element is not one component of the eutectic liquid, the liquid phase will still remain after long dwell times at the bonding temperature, because the composition of the eutectic liquid cannot be
Table 3 The mechanical properties of TLP diffusion bonding joints of the T91 steel with different interlayer Interlayer
Temperature (◦ C)
BNi2 Fe78 Si9 B13
1225
FeNiCrSiB
1225 1250
Tensile strengths (MPa)
Bend strengths (MPa)
Break position
358 736 780 860
100 400 679 980
Joints Joints Base metal
116
S.J. Chen et al. / Materials Science and Engineering A 499 (2009) 114–117
Fig. 2. Back-scattered electron image and major element content distribution of T91 steel TLP bonding joints with different interlayers (bonding conditions: (a, b and c) 1225 ◦ C for 3 min and (d) 1250 ◦ C for 3 min).
obviously changed during bonding. The liquid solidifies gradually only when the temperature is decreased. Such a bonding process can be termed brazing. On the other hand, if the active element is involved in the eutectic reaction, such a bonding technique can be termed TLP bonding. It is obvious that with the progress of
the interface reaction between active element and parent material, the composition of the eutectic liquid phase will be changed, and the melting point of the eutectic alloy will be increased along the liquidus and the liquid phase will solidify at the bonding temperature.
S.J. Chen et al. / Materials Science and Engineering A 499 (2009) 114–117
The interface reaction is complicated and there are many factors to ascribe to the reaction including bonding pressure, temperature, dwell time, surface condition of the mating surface, heat treatment status of the parent materials, ambient gas, etc. In the present study, the main thermodynamic factors, i.e. bonding pressure, bonding temperature and dwell time at elevated temperature, were investigated in detail to clarify the interface reaction and interface evolution during bonding. Because the diffusion of MPD into the parent materials is the controlling factor for TLP bonding, all parameters concerned with the diffusion process of MPD will contribute to the TLP bonding process. Based on the characteristics of the TLP bonding process, the bonding temperature should be high enough so that the liquid phase is stable and the diffusion driving force of MPD atoms is high enough to overcome the obstacle of diffusion potential. Generally speaking, the bonding temperature employed in TLP bonding process should meet the following conditions: (1) it should be high enough so that the interlayer is fully or partially in the liquid state; (2) in order to shorten the dwell time which is needed for the isothermal solidification of the liquid phase, any undesirable intermetallics should be avoided so that MPD atoms can have a high diffusion coefficient; 1250 ◦ C has been chosen as the lowest bonding temperature in the present study. Fig. 1 shows the morphology of the joint produced at 1250 ◦ C. Compared with 1225 ◦ C used FeNiCrSiB interlayer, some differences can clearly be seen: 1250 ◦ C process has been significantly strengthened by the increase in temperature, there is no continuous white strip in the interlayer. Dwell time is also very important for TLP bonding. Dwell time at bonding temperature must be long enough so that a liquid region with sufficient thickness will be formed and flow to fill any voids formed at the interface. As shown above, obtaining a sound interface TLP-bond between interlayer and T91 is a decisive process in manufacturing a defectfree joint of T91. So it is important to investigate the joint formation process in order to optimize the experimental parameters and obtain a good understanding of the bonding process [7].
117
5. Conclusions Based on the experimental results and discussion, the following conclusions can be drawn: (i) A novel interlayer based on the ternary FeNiCrSiB system is found to be a suitable interlayer for TLP bonding giving T91 steel. No bonding defects have been observed at the interface where the T91 joint bonded at 1250 ◦ C for 3 min under 6 MPa with FeNiCrSiB interlayer. (ii) TLP bonding using the Fe78 Si9 B13 interlayer produces nearparent metal properties, however, the high concentrations of boron present in the vicinity of the joint appear to have an embrittling effect. (iii) TLP bonding using the nickel-base amorphous foil BNi2 , resulted in a bond region stabilized by the high nickel concentration. The high concentration of nickel present in the core of the joint was found to reduce the joint strengths. Acknowledgements The authors would like to thank Shandong Electric Power College of China for financial supports. They also wish to acknowledge Professor X.G. Li in the Shandong Electric Power College (Jinan, China) for supporting the research. References [1] [2] [3] [4] [5] [6] [7]
W.F. Gale, D.A. Butts, Sci. Tech. Weld. Join. 9 (2004) 283–300. H. Duan, M. Kocak, K.H. Bohm, V. Ventzke, Sci. Tech. Weld. Join. 9 (2004) 513–518. G. Cam, M. Kocak, Int. Mater. Rev. 43 (1998) 1–30. T.I. Khan, E.R. Wallach, J. Mater. Sci. 30 (1995) 5151–5160. Y.N. Liang, M.I. Osendi, P. Miranzo, J. Eur. Ceram. Soc. 23 (2003) 547–553. E. Lugscheider, T. Cosack, Weld. Res. 10 (1998) 215–221. S.J. Chen, X.T. Jing, X.G. Li, Trans. Chin. Weld. Inst. 25 (2004) 73–76.