Diffusion bonding of titanium alloy to micro-duplex stainless steel using a nickel alloy interlayer: Interface microstructure and strength properties

摘要

In the present study, diffusion bonding of titanium alloy and micro-duplex stainless steel with a nickel alloy interlayer was carried out in the temperature range of 800-950 ℃ for 45 min under the compressive stress of 4 MPa in a vacuum. The bond interfaces were characterised by scanning electron microscopy, electron probe microanalyzer and X-ray diffraction analysis. The layer wise Ni_3Ti, NiTi and NiTi_2 interme-tallics were observed at the nickel alloy/titanium alloy interface and irregular shaped particles of Fe_(22)Mo_(20)Ni_(45)Ti_(13) was observed in the Ni_3Ti intermetallic layer. At 950 ℃ processing temperature, black island of p-Ti phase has been observed in the NiTi_2 intermetallics. However, the stainless steelickel alloy interface indicates the free of intermetallics phase. Fracture surface observed that, failure takes place through the NiTi_2 phase at the NiA-TiA interface when bonding was processed up to 900 ℃, however, failure takes place through NiTi_2 and p-Ti phase mixture for the diffusion joints processed at 950 ℃. Joint strength was evaluated and maximum tensile strength of ~560MPa and shear strength of ~415 MPa along with ~8.3% ductility were obtained for the diffusion couple processed at 900 ℃ for 45 min.