Diffusion bonding of implantable Al2O3/Ti-13Nb-13Zr joints: Interfacial microstructure and mechanical properties

The development of welding technology for zirconium alloy has great significance on the safety, stability, and reliability of the operation of the nuclear reactor. In this work, vacuum diffusion bonding of Zr-4 alloy was studied at the diffusion temperature ranging from 760 to 820 °C with holding times of 30–90 min. The effects of diffusion bonding temperature and holding time on the interfacial microstructure and mechanical properties of the diffusion bonded Zr-4 alloy joints were investigated in detail, and the relationship between the interfacial microstructure and shear strength of the diffusion bonded joints was discussed. The results show that the interface bonding ratio of the diffusion bonded Zr-4 joint gradually increased from 74% to 95% with the increasing of bonding temperature. In addition, the grain size of the base material became a larger and brittle second phase composed of Zr(Cr, Fe)2 and eutectic α-Zr + Zr(Fe, Cr)2 formed in the joint with the increase of the temperature as well as the extension of the bonding time. The highest shear strength of 349 MPa was obtained at 800 °C for 30 min under 7 MPa, and the crack of the joint was primarily propagated along with the base material rather than the bonded interface.

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Diffusion Bonding of Ti2AlNb Alloy and High-Nb-Containing TiAl Alloy: Interfacial Microstructure and Mechanical Properties

Metals ◽

10.3390/met8121061 ◽

2018 ◽

Vol 8 (12) ◽

pp. 1061 ◽

Cited By ~ 4

Author(s):

Hong Bian ◽

Yuzhen Lei ◽

Wei Fu ◽

Shengpeng Hu ◽

Xiaoguo Song ◽

...

Keyword(s):

Mechanical Properties ◽

Diffusion Bonding ◽

Tial Alloy ◽

Energy Dispersive Spectrometer ◽

Bonding Temperature ◽

Interfacial Microstructure ◽

Holding Time ◽

Interfacial Structure ◽

Microstructure And Mechanical Properties ◽

O Phase

In this study, reliable Ti2AlNb/high-Nb-containing TiAl alloy (TAN) joints were achieved by diffusion bonding. The effects of bonding temperature and holding time on the interfacial microstructure and mechanical properties were fully investigated. The interfacial structure of joints bonded at various temperatures and holding times was characterized by scanning electron microscopy (SEM), energy dispersive spectrometer (EDS) and X-ray diffraction (XRD). The results show that the typical microstructure of the Ti2AlNb substrate/O phase/Al(Nb,Ti)2 + Ti3Al/Ti3Al/TAN substrate was obtained at 970 °C for 60 min under a pressure of 5 MPa. The formation of the O phase was earlier than the Al(Nb,Ti)2 phase when bonding temperature was relatively low. When bonding temperature was high enough, the Al(Nb,Ti)2 phase appeared earlier than the O phase. With the increase of bonding temperature and holding time, the Al(Nb,Ti)2 phase decomposed gradually. As the same time, continuous O phase layers became discontinuous and the Ti3Al phase coarsened. The maximum bonding strength of 66.1 MPa was achieved at 970 °C for 120 min.

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