Diffusion Bonding of SP-700 Titanium Alloy with Different Process Parameters AITranslate
Abstract AITranslate
Diffusion bonding （DB）is a highly effective technique for joining titanium alloys with equivalent strength，which avoids the defects caused by metal melting and solidification in the traditional titanium alloy welding process. DB is a good choice for many products，such as the high-speed rail，aircraft，space vehicles and so on. Ti-6Al-4V exhibits exceptional comprehensive performance，which accounts for 50% of the total output of titanium alloy at present. However，its processing difficulties lead to high cost and high price of products. Consequently，alternative materials with reduced processing operations and superior structural performance have been developed to replace Ti-6Al-4V. Compared to Ti-6Al-4V，SP-700 titanium alloy has been formulated to possess improved hot formability and machinability. The appropriate processing parameters were investigated and the impact of equiaxed and lamellar structures on the properties of SP-700 titanium alloy sheet diffusion bonding joints was explored. Experimental DB trails were conducted on SP-700 titanium alloy under 760~940 ℃ （2 MPa，2 h），0.5~2 MPa （780 ℃，2 h），1~4 h （780 ℃，2 MPa）. Uniaxial tensile specimens and shear specimens were employed to evaluate the properties of the matrix and the joints. The microstructure and fracture mechanism of the joints were analyzed using optical microscopy （OM）and scanning electron microscopy （SEM）. The results showed that：at 760~900 ℃ （2 MPa，2 h），the yield strength of the matrix gradually decreased with the increase of temperature. At 760 ℃/2 h/2 MPa，the yield strength reached peak value of 1020.3 MPa. The tensile strength of the matrix exhibited a W-shaped trend with increasing temperature. At 860 ℃，the maximum tensile strength of 1115.3 MPa was achieved under 2 MPa and 2 h. The yield strength of the matrix decreased slightly with the increase of pressure. The yield strength of the matrix under 0.5 and 2 MPa （780 ℃，2 h）was 1014.8 and 988.6 MPa，respectively. The tensile strength showed a consistent trend，with values of 1088.1 and 1068.8 MPa，respectively. When the time changed，the yield strength and tensile strength of the matrix after 4 h were significantly higher than those of 1 and 2 h （780 ℃，2 MPa）. 4 h sample demonstrated a tensile strength and yield strength of 1105.9 MPa and 1019 MPa，which were 37.1 MPa and 30.4 MPa higher than those of 2 h sample. With the increase of temperature，pressure，and time，the occurrence of holes and bonding interface diminished，leading to an enhancement of shear strength. SP-700 titanium alloy joint formed at 760 ℃ exhibited bonding interface and large interface pores，indicating suboptimal bonding quality with a shear strength of 410 MPa. With the diffusion bonding process of 780 ℃/2 h/2 MPa，the interface achieved complete bonding，resulting in a shear strength of 490.9 MPa. Under the diffusion bonding process parameters of 860 ℃/2 h/2 MPa，the grains occurred equiaxed coarsening，and both the bonding interface and micropores vanished entirely，facilitating robust bonding between the materials. This configuration exhibited the highest interface bonding strength of 589 MPa. When the bonding pressure was 0.5 MPa，the shear strength of the joint was 443 MPa. Increasing the diffusion bonding pressure to 2 MPa elevated the shear strength by 47.9 MPa. When the time was 1 h，the shear strength was 299.8 MPa，while extending the diffusion bonding time to 4 h enhanced the shear strength by 282.3 MPa. The impact of temperature and time was more pronounced than that of pressure on the quality of diffusion bonding and shear strength. According to the fourth strength theory，the shear strength of the sample at 860 ℃ was consistent with that of the matrix. When the diffusion bonding temperature was higher than 900 ℃，the microstructure type was transformed into a lamellar structure. Although the interface was completely bonded，the mechanical properties of the joint decreased due to the weakened properties of the base metal. This phenomenon underscored the influence of temperature on the plastic deformation，diffusion coefficient，and disappearance of surface protrusion area interface voids during the initial connection stage. Higher temperatures conferred greater plastic deformation capacity to the material，and the diffusion coefficient increased accordingly. Consequently，higher bonding temperatures and pressures supplied additional energy for atomic diffusion，resulting in improved bonding quality. However，excessively high temperature would cause phase transformation of the base metal，which would significantly reduce the performance of the matrix. Therefore，the diffusion bonding temperature of SP-700 titanium alloy should be selected inα+βphase region rather thanβphase region. At low bonding rate （low temperature，short time），the shear fracture morphology presented granular fracture zone and intergranular dissociation fracture，while at high bonding rate （high temperature，long time），the shear fracture mode gradually changed from brittle fracture to brittle+ductile mixed fracture.
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Basic Information:
DOI：10.13373/j.cnki.cjrm.XY23100024
Chinese Library Classification Number:TG146.2
Citation Information:
Diffusion bonding （DB）is a highly effective technique for joining titanium alloys with equivalent strength，which avoids the defects caused by metal melting and solidification in the traditional titanium alloy welding process. DB is a good choice for many products，such as the high-speed rail，aircraft，space vehicles and so on. Ti-6Al-4V exhibits exceptional comprehensive performance，which accounts for 50% of the total output of titanium alloy at present. However，its processing difficulties lead to high cost and high price of products. Consequently，alternative materials with reduced processing operations and superior structural performance have been developed to replace Ti-6Al-4V. Compared to Ti-6Al-4V，SP-700 titanium alloy has been formulated to possess improved hot formability and machinability. The appropriate processing parameters were investigated and the impact of equiaxed and lamellar structures on the properties of SP-700 titanium alloy sheet diffusion bonding joints was explored. Experimental DB trails were conducted on SP-700 titanium alloy under 760~940 ℃ （2 MPa，2 h），0.5~2 MPa （780 ℃，2 h），1~4 h （780 ℃，2 MPa）. Uniaxial tensile specimens and shear specimens were employed to evaluate the properties of the matrix and the joints. The microstructure and fracture mechanism of the joints were analyzed using optical microscopy （OM）and scanning electron microscopy （SEM）. The results showed that：at 760~900 ℃ （2 MPa，2 h），the yield strength of the matrix gradually decreased with the increase of temperature. At 760 ℃/2 h/2 MPa，the yield strength reached peak value of 1020.3 MPa. The tensile strength of the matrix exhibited a W-shaped trend with increasing temperature. At 860 ℃，the maximum tensile strength of 1115.3 MPa was achieved under 2 MPa and 2 h. The yield strength of the matrix decreased slightly with the increase of pressure. The yield strength of the matrix under 0.5 and 2 MPa （780 ℃，2 h）was 1014.8 and 988.6 MPa，respectively. The tensile strength showed a consistent trend，with values of 1088.1 and 1068.8 MPa，respectively. When the time changed，the yield strength and tensile strength of the matrix after 4 h were significantly higher than those of 1 and 2 h （780 ℃，2 MPa）. 4 h sample demonstrated a tensile strength and yield strength of 1105.9 MPa and 1019 MPa，which were 37.1 MPa and 30.4 MPa higher than those of 2 h sample. With the increase of temperature，pressure，and time，the occurrence of holes and bonding interface diminished，leading to an enhancement of shear strength. SP-700 titanium alloy joint formed at 760 ℃ exhibited bonding interface and large interface pores，indicating suboptimal bonding quality with a shear strength of 410 MPa. With the diffusion bonding process of 780 ℃/2 h/2 MPa，the interface achieved complete bonding，resulting in a shear strength of 490.9 MPa. Under the diffusion bonding process parameters of 860 ℃/2 h/2 MPa，the grains occurred equiaxed coarsening，and both the bonding interface and micropores vanished entirely，facilitating robust bonding between the materials. This configuration exhibited the highest interface bonding strength of 589 MPa. When the bonding pressure was 0.5 MPa，the shear strength of the joint was 443 MPa. Increasing the diffusion bonding pressure to 2 MPa elevated the shear strength by 47.9 MPa. When the time was 1 h，the shear strength was 299.8 MPa，while extending the diffusion bonding time to 4 h enhanced the shear strength by 282.3 MPa. The impact of temperature and time was more pronounced than that of pressure on the quality of diffusion bonding and shear strength. According to the fourth strength theory，the shear strength of the sample at 860 ℃ was consistent with that of the matrix. When the diffusion bonding temperature was higher than 900 ℃，the microstructure type was transformed into a lamellar structure. Although the interface was completely bonded，the mechanical properties of the joint decreased due to the weakened properties of the base metal. This phenomenon underscored the influence of temperature on the plastic deformation，diffusion coefficient，and disappearance of surface protrusion area interface voids during the initial connection stage. Higher temperatures conferred greater plastic deformation capacity to the material，and the diffusion coefficient increased accordingly. Consequently，higher bonding temperatures and pressures supplied additional energy for atomic diffusion，resulting in improved bonding quality. However，excessively high temperature would cause phase transformation of the base metal，which would significantly reduce the performance of the matrix. Therefore，the diffusion bonding temperature of SP-700 titanium alloy should be selected inα+βphase region rather thanβphase region. At low bonding rate （low temperature，short time），the shear fracture morphology presented granular fracture zone and intergranular dissociation fracture，while at high bonding rate （high temperature，long time），the shear fracture mode gradually changed from brittle fracture to brittle+ductile mixed fracture.
quote
| GB/T 7714-2015 | [1] Jue Wang, Minggang Liu, Xiaowei Zhang, et al. Diffusion Bonding of SP-700 Titanium Alloy with Different Process Parameters[J]. Chinese Journal of Rare Metals, 2025, 49(6): 807-815. DOI:10.13373/j.cnki.cjrm.XY23100024. |
| MLA | [1] Jue Wang, et al., "Diffusion Bonding of SP-700 Titanium Alloy with Different Process Parameters." Chinese Journal of Rare Metals, vol. 49, no. 6, 2025, pp. 807-815, https://doi.org/10.13373/j.cnki.cjrm.XY23100024. |
| APA | [1] Jue Wang, Minggang Liu, Xiaowei Zhang, Li Zhu, Yuelin Wang, & Tianzhang Zhao. (2025). Diffusion Bonding of SP-700 Titanium Alloy with Different Process Parameters. Chinese Journal of Rare Metals, 49(6), 807-815. https://doi.org/10.13373/j.cnki.cjrm.XY23100024 |
| IEEE | [1] Jue Wang, Minggang Liu, Xiaowei Zhang, Li Zhu, Yuelin Wang, and Tianzhang Zhao, "Diffusion Bonding of SP-700 Titanium Alloy with Different Process Parameters," Chinese Journal of Rare Metals, vol. 49, no. 6, pp. 807-815, 2025, doi: 10.13373/j.cnki.cjrm.XY23100024. keywords: {SP-700 titanium alloy;diffusion bonding;uniaxial tensile;shear strength;microstructure} |