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Autogeneous pressure-assisted interlayer-free diffusion bonding of Ti(C,N)-based cermet and steel
Materials Letters 135 (2014) 27–30
Contents lists available at ScienceDirect
Materials Letters journal homepage: www.elsevier.com/locate/matlet
Autogeneous pressure-assisted interlayer-free diffusion bonding of Ti(C,N)-based cermet and steel Zhixing Guo a, Hua Zhong a, Mei Yang b, Ji Xiong a,n, Weicai Wan a, Mengxia Liang a a b
School of Manufacturing Science and Engineering, Sichuan University, Chengdu 610065, PR China College of Materials and Chemistry & Chemical Engineering, Chengdu University of Technology, Chengdu 610059, PR China
art ic l e i nf o
a b s t r a c t
Article history: Received 26 April 2014 Accepted 19 July 2014 Available online 30 July 2014
A diffusion bonding technique free of interlayer and external pressure was introduced, and the bonding pressure was generated due to linear shrinkage of Ti(C,N)-based cermet and thermal expansion of steel. The Ti, Ni, Fe concentrations across the joint evolved gradually and binder-riched surface layer, Fe–Co bonded cermet layer and austenite layer formed successively. The tensile residual stress decreased and the stress concentration region transferred away from the cermet side to the steel side. Diffusion bonding was combined with the liquid phase sintering process, and the cermet substrate need not to be heated twice. Compared with traditional method, the joint strength is improved due to graded microstructure, residual stress decrease and bonding process simplification. & 2014 Elsevier B.V. All rights reserved.
Keywords: Welding Diffusion Cermet Gradient zones Residual stress
1. Introduction Ti(C,N)-based cermets have been successfully utilized for moulds, seals and indexable inserts [1] and considered as a potential alternative material for tungsten carbide. Since wear and corrosion usually occur on the surface of materials, cermets are joined with metals to make full use of their high hardness and wear resistance and save rare metals as Ti, Mo and Co. Faced with the challenge of poor wettability and coefficient of thermal expansion (CTE) mismatch, active metals such as BNi-2 [2], Ag– Cu–Zn [3], Al/Ni [4], Ti, Ti/Mo and Ti/Cu [5,6] and external pressure [4–6] are used during joining. However, it is difficult to exert pressure on some components of cylinder type. Song [7] and Guo [8] reported that diffusion bonding of Ti–6Al–4V and ZQSn10-10 could be achieved with Ni or Ni/Cu interlayer, and the diffusion pressure was produced by different CTE of the substrates. Zhang [9] joined TiC cermet and steel with Ag–Cu–Zn filler, and the bonding stress was generated by the restraint of steel expansion. However, interlayers, as dissimilar materials indeed, lead to the microstructure and property discontinuity across the joint. Furthermore, the process is somehow complicated since the cermet substrates have to be sintered firstly and then bonded with steel. In the paper, diffusion bonding is carried out by an autogeneous pressure-assisted interlayer-free (APAIF) method, during which the pressure is generated by the shrinkage of cermet
during bonding and the linear expansion of steel to the opposite direction. The bonding process, microstructure, composition and residual stress across the joint are investigated and compared with traditional method.
2. Experimental procedures APAIF process consists of three steps as shown in Fig. 1. First, cylindrical cermet compact with an internal diameter of 8.6 mm, external diameter of 21.0 mm and height of 12.4 mm is pressed using Ti(C,N)–10Mo2C–40Co powder mixture. Second, AISI 1045 steel bar with an external diameter of 7.0 mm and height of 10 mm is placed into the cermet cylinder forming a clearance of 1.6 mm. Finally, the cermet compact and steel are placed on Al2O3 ceramic plates, and diffusion bonding is achieved by directly heating to 1593 K in a vacuum furnace. Traditional method contains four steps. The first step is the same with APAIF method. However, before the assembly of the cermet and steel substrate, the cermet compact is vacuum sintered at 1593 K. Then 0.3 mm active (Ag, Cu)–Cu–(Ag,Cu) multi-interlayer is placed between the steel and as-sintered cermet substrate during assembly. Finally bonding is achieved by heating to 1073 K.
3. Results and discussion n
Corresponding author. Tel.: þ 86 13880085119; fax: þ 86 28 85196764. E-mail address: [email protected] (J. Xiong).
http://dx.doi.org/10.1016/j.matlet.2014.07.136 0167-577X/& 2014 Elsevier B.V. All rights reserved.
The bonding temperature of APAIF method is determined to be 1593 K from the eutectic temperature of Ti(C,N)-based cermet
28
Z. Guo et al. / Materials Letters 135 (2014) 27–30
reported by Andrén [10]. Liquid phase sintering of cermet occurs at this temperature [11], resulting in the linear shrinkage of the compact [12]. The cermet internal diameter is deduced to decrease to 7.0 mm at 1593 K since the linear shrinkage of cermet is measured to be 18.7%. The linear CTE of steel was calculated to be 10–15 10 6/K according to the Debye–Grüneisen model modified by Lu [13], and the external diameter of steel is calculated to increase to 7.1 mm at 1593 K. Therefore, the clearance between steel and cermet experiences a gradual decrease and disappears when they contact. Autogeneous pressure forms due to further shrinkage and expansion of them at an elevated temperature, noting that a so-called interference fit of about 0.1 mm appears from the above calculation. Fig. 2 shows the microstructure and concentration profiles across the joint by APAIF and traditional method, and the top inset are the enlarged view of the bonding zones. Obvious diffusion can be seen in Fig. 2a since there is a gradual decrease of Ti, Co and Mo concentrations, and increase of Fe element from the cermet side to steel side. The cermet shows typical core/rim structure, the cores are essentially undissolved Ti(C,N) particles or (Ti,Mo)(C,N) solid solutions with relatively lower Mo and higher Ti content, the rims are (Mo,Ti)(C,N) solid solution with relatively higher Mo but lower Ti content [3], and the core/rim structures are surrounded by Co-based binder. Since elements with larger atom number show lighter color when observed by SEM in BSE mode, the core appears black, the rim is grey, and the binder is white.
Fig. 1. Schematic illustrations of APAIF and traditional bonding method.
Zone A is the surface layer of cermet substrate of about 65 μm. It shows similar microstructure with cermet substrate but of larger binder content and less core–rim phase. The larger binder content stems from the diffusion of Fe from steel. Furthermore, Ti(C,N) is expected to decompose at sintering temperature under denitriding conditions, thus generating a gradual decrease of N activity towards the surface. Due to the thermodynamic coupling between N and Ti, the outward diffusion of N lead to inward diffusion of Ti, yielding a thin surface layer of low N and Ti and enriched in Co binder. The coupling may be expressed by the off-diagonal coefficients of the diffusion coefficient matrix Dnkj of the Fick– Onsager diffusion equation [14], n1
J k ¼ ∑ Dnkj j¼1
∂cj ∂z
ð1Þ
where J k is the diffusion flux of species k, ð∂cj Þ=ð∂z Þ is the concentration gradient of species j. The integer n denotes a species which is arbitrarily chosen as Ref. [14]. Zone B is essentially Ti(C, N)-based cermet of 40 μm with still higher Fe/Co binder. The Ti(C, N) hard phase appears grey without obvious core–rim structure since there is not much Mo in the zone for the formation of (Mo,Ti) (C,N) rim. Zone C is an austenite layer of about 200 μm, which is characterized by a gradual Co decrease and Fe increase. Co is known as an austenitising element, suppressing the formation of α-ferrite during cooling [15]. Austenite forms since the Co is about 25% in zone C from EDS. Zone C appears blank since the austenite can't be etched by Nital solution as the pearlite steel substrate. The steel substrate shows typical pearlite-based microstructure. It is difficult for Ti, Mo and Co element in cermet to diffuse into steel due to the long distance. The nominal compositions of the bonding zones are deduced from EDS and listed in Table 1, and only a trace of the above elements is detected in steel. It can be deduced that the bonding zones by APAIF method are not strictly distinguished, and the microstructure and compositions change gradually across the joint. Fig. 2b shows separated bonding zones with sandwich structure, which is originated from the as-received interlayer metals. Zone A is about 100 μm and composed of duplex phases. The black blocks are Cu-riched solid solution (Cu(s.s)) and the white strips are Ag-riched solid solution (Ag(s.s)). Zone B is 165 μm, which is a Cu layer and appearing black. Zone C is of similar microstructure with Zone A with a thickness of 40 μm. The reaction and element diffusion between interlayer and cermet/steel substrates are slight due to lower bonding temperature [3].
Fig. 2. Microstructure and concentration profiles across the joint by (a) APAIF and (b) traditional bonding method.
Z. Guo et al. / Materials Letters 135 (2014) 27–30
29
Table 1 Nominal compositions of the bonding zones. Zones
APAIF method
Traditional method
Cermet substrate Zone A Zone B Zone C Steel substrate
50 Ti(C,N)–10Mo2C–40Co–0Fe 37 Ti(C,N)–8Mo2C–45Co–10Fe 24 Ti(C,N)–6Mo2C–50Co–20Fe 6 Ti(C,N)–4Mo2C–25Co–65Fe 0 Ti(C,N)–0Mo2C–0Co–100(Fe–0.45C)
50Ti(C,N)–10Mo2C–40Co Cu60–Ag40 Cu Cu60–Ag40 Fe–0.45C
Fig. 3. Contour maps of residual stress distribution across the joint by (a) APAIF and (b) traditional bonding method.
The residual stress is estimated by finite element modeling using a two-dimensional axisymmetric continuum model. In view of the symmetry of the joint, only half of the joint is modelled. The elements used are continuum-based four-node axisymmetric with full integration type. The metallic materials are assumed to behave in an elasto-plastic manner, the boundary condition used is that the nodes on the bottom of cermet cylinder (y¼0) do not displace in the y-direction and no external loads are used in these simulations. Fig. 3 shows the contour maps of residual stress cross the joints. The bottom right insets give the magnified view of the residual stress concentration (RSC) regions. As for the joint by APAIF method, the gradient bonding zones diminish the microstructure and concentration difference between cermet and steel. Such a situation is highly desirable as it helps to decrease the residual stresses level, hence acts effectively as a stress relief structure. The maximum residual stress value r is larger in the joint by traditional method. The RSC regions is located in the vicinity of cermet surface and zone A, which is similar to the results of former studies on ceramics–metal joining [16]. However, the RSC region transfers from the brittle cermet side to the tough steel side (zone C) by APAIF method. The average shear strength of the joint by APAIF method is tested to be 117.5 MPa, compared with 95.2 MPa of traditional method. On the one hand, the enhancement of shear strength can be attributed to the graded interface microstructure, which minished the difference between cermet and steel. On the other hand, the decrease of maximum residual stress and the transferring of the RSC region to the tougher steel substrate can also enhance the reliability of the joint.
4. Conclusion A diffusion bonding method in the absence of external pressure and interlayer is developed to join cermet and steel dissimilar materials. The Ti and Co element diffuse towards the steel, and Fe element diffuse in the opposite direction. Gradient interface areas including binder-riched surface layer, Fe–Co bonded cermet layer and austenite layer formed between the substrates, compared with the Ag(s.s) þCu(s.s),Cu,Ag(s.s) þCu(s.s) separated zones forming in the joint by the traditional method. The interface structure change result in the decrease of tensile residual stress value and its location transferring away from cermet side to steel side. Therefore, the APAIF method is favorable to the enhancement of shear strength, and reliability joint is achieved.
Acknowledgements The work is financially supported by National Natural Science Foundation of China (no. 51205263), Fundamental Research Funds for the Central Universities (no. 2013SCU04A30) and Sichuan Science and Technology Project (no. 2013GZX0146). References [1] Ahn SY, Kang S. Scr Mater 2006;55:1015–8. [2] Wang FZ, Wang QZ, Yu BH, Xiao BL, Ma ZY. J Mater Process Technol 2011;211:1804–9. [3] Zhang LX, Feng JC, Zhang BY, Jing XM. Mater Lett 2005;59:110–3. [4] Cao J, Song XG, Wu LZ, Qi JL, Feng JC. Thin Solid Films 2012;520:3528–31.
30
Z. Guo et al. / Materials Letters 135 (2014) 27–30
[5] Travessa D, Ferrante M, Ouden Gert den. Mater Sci Eng A 2002;337:287–96. [6] Kliauga AM, Travessa D, Ferrante M. Mater Charact 2001;46:65–74. [7] Song MX, Zhao XH, Hang D, Guo W, Feng JC. Rare Met Mater Eng 2007;36:1938–41. [8] Guo W, Zhao XH, Song MX, Feng JC, Yang B. J Mater Sci Technol 2006;22:817–20. [9] Zhang LX, Feng JC, He P. Mater Sci Eng, A 2006;428:24–33. [10] Andrén HO, Rolander U, Lindahl P. Int J Refract Met Hard Mater 19931994;12:107–13. [11] Córdoba JM, Chicardi E, Gotor FJ. J Alloys Compd 2013;559:34–8.
[12] Mohsin IU, Lager D, Gierl C, Hohenauer W, Danninger H. Mater Lett 2010;64:2347–9. [13] Lu XG, Selleby M, Sundman B. Acta Mater 2005;53:2259–72. [14] Ekroth M, Frykholm R, Lindhol M, Andren H-O, Agren J. Acta Mater 2000;48:2177–85. [15] Helisa L, Toda Y, Hara T, Miyazaki H, Abe F. Mater Sci Eng, A 2009;510511:88–94. [16] Laik A, Mishra P, Bhanumurthy K, Kale GB, Kashyap BP. Acta Mater 2013;61:126–38.
Contents lists available at ScienceDirect
Materials Letters journal homepage: www.elsevier.com/locate/matlet
Autogeneous pressure-assisted interlayer-free diffusion bonding of Ti(C,N)-based cermet and steel Zhixing Guo a, Hua Zhong a, Mei Yang b, Ji Xiong a,n, Weicai Wan a, Mengxia Liang a a b
School of Manufacturing Science and Engineering, Sichuan University, Chengdu 610065, PR China College of Materials and Chemistry & Chemical Engineering, Chengdu University of Technology, Chengdu 610059, PR China
art ic l e i nf o
a b s t r a c t
Article history: Received 26 April 2014 Accepted 19 July 2014 Available online 30 July 2014
A diffusion bonding technique free of interlayer and external pressure was introduced, and the bonding pressure was generated due to linear shrinkage of Ti(C,N)-based cermet and thermal expansion of steel. The Ti, Ni, Fe concentrations across the joint evolved gradually and binder-riched surface layer, Fe–Co bonded cermet layer and austenite layer formed successively. The tensile residual stress decreased and the stress concentration region transferred away from the cermet side to the steel side. Diffusion bonding was combined with the liquid phase sintering process, and the cermet substrate need not to be heated twice. Compared with traditional method, the joint strength is improved due to graded microstructure, residual stress decrease and bonding process simplification. & 2014 Elsevier B.V. All rights reserved.
Keywords: Welding Diffusion Cermet Gradient zones Residual stress
1. Introduction Ti(C,N)-based cermets have been successfully utilized for moulds, seals and indexable inserts [1] and considered as a potential alternative material for tungsten carbide. Since wear and corrosion usually occur on the surface of materials, cermets are joined with metals to make full use of their high hardness and wear resistance and save rare metals as Ti, Mo and Co. Faced with the challenge of poor wettability and coefficient of thermal expansion (CTE) mismatch, active metals such as BNi-2 [2], Ag– Cu–Zn [3], Al/Ni [4], Ti, Ti/Mo and Ti/Cu [5,6] and external pressure [4–6] are used during joining. However, it is difficult to exert pressure on some components of cylinder type. Song [7] and Guo [8] reported that diffusion bonding of Ti–6Al–4V and ZQSn10-10 could be achieved with Ni or Ni/Cu interlayer, and the diffusion pressure was produced by different CTE of the substrates. Zhang [9] joined TiC cermet and steel with Ag–Cu–Zn filler, and the bonding stress was generated by the restraint of steel expansion. However, interlayers, as dissimilar materials indeed, lead to the microstructure and property discontinuity across the joint. Furthermore, the process is somehow complicated since the cermet substrates have to be sintered firstly and then bonded with steel. In the paper, diffusion bonding is carried out by an autogeneous pressure-assisted interlayer-free (APAIF) method, during which the pressure is generated by the shrinkage of cermet
during bonding and the linear expansion of steel to the opposite direction. The bonding process, microstructure, composition and residual stress across the joint are investigated and compared with traditional method.
2. Experimental procedures APAIF process consists of three steps as shown in Fig. 1. First, cylindrical cermet compact with an internal diameter of 8.6 mm, external diameter of 21.0 mm and height of 12.4 mm is pressed using Ti(C,N)–10Mo2C–40Co powder mixture. Second, AISI 1045 steel bar with an external diameter of 7.0 mm and height of 10 mm is placed into the cermet cylinder forming a clearance of 1.6 mm. Finally, the cermet compact and steel are placed on Al2O3 ceramic plates, and diffusion bonding is achieved by directly heating to 1593 K in a vacuum furnace. Traditional method contains four steps. The first step is the same with APAIF method. However, before the assembly of the cermet and steel substrate, the cermet compact is vacuum sintered at 1593 K. Then 0.3 mm active (Ag, Cu)–Cu–(Ag,Cu) multi-interlayer is placed between the steel and as-sintered cermet substrate during assembly. Finally bonding is achieved by heating to 1073 K.
3. Results and discussion n
Corresponding author. Tel.: þ 86 13880085119; fax: þ 86 28 85196764. E-mail address: [email protected] (J. Xiong).
http://dx.doi.org/10.1016/j.matlet.2014.07.136 0167-577X/& 2014 Elsevier B.V. All rights reserved.
The bonding temperature of APAIF method is determined to be 1593 K from the eutectic temperature of Ti(C,N)-based cermet
28
Z. Guo et al. / Materials Letters 135 (2014) 27–30
reported by Andrén [10]. Liquid phase sintering of cermet occurs at this temperature [11], resulting in the linear shrinkage of the compact [12]. The cermet internal diameter is deduced to decrease to 7.0 mm at 1593 K since the linear shrinkage of cermet is measured to be 18.7%. The linear CTE of steel was calculated to be 10–15 10 6/K according to the Debye–Grüneisen model modified by Lu [13], and the external diameter of steel is calculated to increase to 7.1 mm at 1593 K. Therefore, the clearance between steel and cermet experiences a gradual decrease and disappears when they contact. Autogeneous pressure forms due to further shrinkage and expansion of them at an elevated temperature, noting that a so-called interference fit of about 0.1 mm appears from the above calculation. Fig. 2 shows the microstructure and concentration profiles across the joint by APAIF and traditional method, and the top inset are the enlarged view of the bonding zones. Obvious diffusion can be seen in Fig. 2a since there is a gradual decrease of Ti, Co and Mo concentrations, and increase of Fe element from the cermet side to steel side. The cermet shows typical core/rim structure, the cores are essentially undissolved Ti(C,N) particles or (Ti,Mo)(C,N) solid solutions with relatively lower Mo and higher Ti content, the rims are (Mo,Ti)(C,N) solid solution with relatively higher Mo but lower Ti content [3], and the core/rim structures are surrounded by Co-based binder. Since elements with larger atom number show lighter color when observed by SEM in BSE mode, the core appears black, the rim is grey, and the binder is white.
Fig. 1. Schematic illustrations of APAIF and traditional bonding method.
Zone A is the surface layer of cermet substrate of about 65 μm. It shows similar microstructure with cermet substrate but of larger binder content and less core–rim phase. The larger binder content stems from the diffusion of Fe from steel. Furthermore, Ti(C,N) is expected to decompose at sintering temperature under denitriding conditions, thus generating a gradual decrease of N activity towards the surface. Due to the thermodynamic coupling between N and Ti, the outward diffusion of N lead to inward diffusion of Ti, yielding a thin surface layer of low N and Ti and enriched in Co binder. The coupling may be expressed by the off-diagonal coefficients of the diffusion coefficient matrix Dnkj of the Fick– Onsager diffusion equation [14], n1
J k ¼ ∑ Dnkj j¼1
∂cj ∂z
ð1Þ
where J k is the diffusion flux of species k, ð∂cj Þ=ð∂z Þ is the concentration gradient of species j. The integer n denotes a species which is arbitrarily chosen as Ref. [14]. Zone B is essentially Ti(C, N)-based cermet of 40 μm with still higher Fe/Co binder. The Ti(C, N) hard phase appears grey without obvious core–rim structure since there is not much Mo in the zone for the formation of (Mo,Ti) (C,N) rim. Zone C is an austenite layer of about 200 μm, which is characterized by a gradual Co decrease and Fe increase. Co is known as an austenitising element, suppressing the formation of α-ferrite during cooling [15]. Austenite forms since the Co is about 25% in zone C from EDS. Zone C appears blank since the austenite can't be etched by Nital solution as the pearlite steel substrate. The steel substrate shows typical pearlite-based microstructure. It is difficult for Ti, Mo and Co element in cermet to diffuse into steel due to the long distance. The nominal compositions of the bonding zones are deduced from EDS and listed in Table 1, and only a trace of the above elements is detected in steel. It can be deduced that the bonding zones by APAIF method are not strictly distinguished, and the microstructure and compositions change gradually across the joint. Fig. 2b shows separated bonding zones with sandwich structure, which is originated from the as-received interlayer metals. Zone A is about 100 μm and composed of duplex phases. The black blocks are Cu-riched solid solution (Cu(s.s)) and the white strips are Ag-riched solid solution (Ag(s.s)). Zone B is 165 μm, which is a Cu layer and appearing black. Zone C is of similar microstructure with Zone A with a thickness of 40 μm. The reaction and element diffusion between interlayer and cermet/steel substrates are slight due to lower bonding temperature [3].
Fig. 2. Microstructure and concentration profiles across the joint by (a) APAIF and (b) traditional bonding method.
Z. Guo et al. / Materials Letters 135 (2014) 27–30
29
Table 1 Nominal compositions of the bonding zones. Zones
APAIF method
Traditional method
Cermet substrate Zone A Zone B Zone C Steel substrate
50 Ti(C,N)–10Mo2C–40Co–0Fe 37 Ti(C,N)–8Mo2C–45Co–10Fe 24 Ti(C,N)–6Mo2C–50Co–20Fe 6 Ti(C,N)–4Mo2C–25Co–65Fe 0 Ti(C,N)–0Mo2C–0Co–100(Fe–0.45C)
50Ti(C,N)–10Mo2C–40Co Cu60–Ag40 Cu Cu60–Ag40 Fe–0.45C
Fig. 3. Contour maps of residual stress distribution across the joint by (a) APAIF and (b) traditional bonding method.
The residual stress is estimated by finite element modeling using a two-dimensional axisymmetric continuum model. In view of the symmetry of the joint, only half of the joint is modelled. The elements used are continuum-based four-node axisymmetric with full integration type. The metallic materials are assumed to behave in an elasto-plastic manner, the boundary condition used is that the nodes on the bottom of cermet cylinder (y¼0) do not displace in the y-direction and no external loads are used in these simulations. Fig. 3 shows the contour maps of residual stress cross the joints. The bottom right insets give the magnified view of the residual stress concentration (RSC) regions. As for the joint by APAIF method, the gradient bonding zones diminish the microstructure and concentration difference between cermet and steel. Such a situation is highly desirable as it helps to decrease the residual stresses level, hence acts effectively as a stress relief structure. The maximum residual stress value r is larger in the joint by traditional method. The RSC regions is located in the vicinity of cermet surface and zone A, which is similar to the results of former studies on ceramics–metal joining [16]. However, the RSC region transfers from the brittle cermet side to the tough steel side (zone C) by APAIF method. The average shear strength of the joint by APAIF method is tested to be 117.5 MPa, compared with 95.2 MPa of traditional method. On the one hand, the enhancement of shear strength can be attributed to the graded interface microstructure, which minished the difference between cermet and steel. On the other hand, the decrease of maximum residual stress and the transferring of the RSC region to the tougher steel substrate can also enhance the reliability of the joint.
4. Conclusion A diffusion bonding method in the absence of external pressure and interlayer is developed to join cermet and steel dissimilar materials. The Ti and Co element diffuse towards the steel, and Fe element diffuse in the opposite direction. Gradient interface areas including binder-riched surface layer, Fe–Co bonded cermet layer and austenite layer formed between the substrates, compared with the Ag(s.s) þCu(s.s),Cu,Ag(s.s) þCu(s.s) separated zones forming in the joint by the traditional method. The interface structure change result in the decrease of tensile residual stress value and its location transferring away from cermet side to steel side. Therefore, the APAIF method is favorable to the enhancement of shear strength, and reliability joint is achieved.
Acknowledgements The work is financially supported by National Natural Science Foundation of China (no. 51205263), Fundamental Research Funds for the Central Universities (no. 2013SCU04A30) and Sichuan Science and Technology Project (no. 2013GZX0146). References [1] Ahn SY, Kang S. Scr Mater 2006;55:1015–8. [2] Wang FZ, Wang QZ, Yu BH, Xiao BL, Ma ZY. J Mater Process Technol 2011;211:1804–9. [3] Zhang LX, Feng JC, Zhang BY, Jing XM. Mater Lett 2005;59:110–3. [4] Cao J, Song XG, Wu LZ, Qi JL, Feng JC. Thin Solid Films 2012;520:3528–31.
30
Z. Guo et al. / Materials Letters 135 (2014) 27–30
[5] Travessa D, Ferrante M, Ouden Gert den. Mater Sci Eng A 2002;337:287–96. [6] Kliauga AM, Travessa D, Ferrante M. Mater Charact 2001;46:65–74. [7] Song MX, Zhao XH, Hang D, Guo W, Feng JC. Rare Met Mater Eng 2007;36:1938–41. [8] Guo W, Zhao XH, Song MX, Feng JC, Yang B. J Mater Sci Technol 2006;22:817–20. [9] Zhang LX, Feng JC, He P. Mater Sci Eng, A 2006;428:24–33. [10] Andrén HO, Rolander U, Lindahl P. Int J Refract Met Hard Mater 19931994;12:107–13. [11] Córdoba JM, Chicardi E, Gotor FJ. J Alloys Compd 2013;559:34–8.
[12] Mohsin IU, Lager D, Gierl C, Hohenauer W, Danninger H. Mater Lett 2010;64:2347–9. [13] Lu XG, Selleby M, Sundman B. Acta Mater 2005;53:2259–72. [14] Ekroth M, Frykholm R, Lindhol M, Andren H-O, Agren J. Acta Mater 2000;48:2177–85. [15] Helisa L, Toda Y, Hara T, Miyazaki H, Abe F. Mater Sci Eng, A 2009;510511:88–94. [16] Laik A, Mishra P, Bhanumurthy K, Kale GB, Kashyap BP. Acta Mater 2013;61:126–38.