Effect of Initial Microstructure on the Plastic Deformation Bonding of Ti64 and Ti17

Joining dissimilar titanium alloys via plastic deformation bonding is quite important for manufacturing complex ‘hybrid’ components in aircraft engines, in which the plastic flow in the bonding interface significantly affects the interfacial void evolution and thus influences the mechanical properties of the joints. The plastic flow in titanium alloys is largely affected by the initial microstructure. Thus, investigation into the interfacial void evolution of dissimilar titanium bonds with different initial microstructures is necessary. In this study, Ti64 (the most widely used α + β two-phase titanium alloy in aerospace industry) with equiaxed microstructure and Ti17 (a near β titanium alloy to fabricate the jet engine and compressor components) with equiaxed microstructure (Ti17-E) and lamellar microstructure (Ti17-L) were joined by plastic deformation bonding. The macroscopic plastic deformation, interfacial void and bonding ratio during bonding of Ti64 and Ti17 were quantitative characterized, and the shear strength of Ti64/Ti17 bonds was obtained. The Ti64/Ti17-E bond showed smaller average interfacial void size and larger bonding ratio than those of Ti64/Ti17-L bond at a certain bonding condition. The large-sized interfacial voids at lower bonding pressure and bonding temperature significantly decreased the shear strength of Ti64/Ti17 bonds due to the formation of un-joined region, and the Ti64/Ti17-E bond at 840 °C, 10 MPa and 30 min almost matched that of the Ti64 due to the promoted interfacial void closure process. The enhanced plastic flow occurred in the Ti64/Ti17-E bonding interface in comparison with that in the Ti64/Ti17-L bonding interface due to the better deformation compatibility of Ti17-E than that of Ti17-L since the preferred slip occurred in the Ti17-L but not in the Ti17-E. The promoted plastic flow and higher temperature rise in the Ti64/Ti17-E bonding interface promoted the void shrinkage process of Ti64/Ti17-E bond. Graphical Abstract: [Figure not available: see fulltext.]