Inertia radial friction welding of Ti60(near-α)/TC18(near-β) bimetallic components: Interfacial bonding mechanism, heterogenous microstructure and mechanical properties

Abstract

Inertia friction welding has emerged as a promising technique for fabricating lightweight and high-strength components in aerospace industry. To achieve high-quality weldments between dissimilar titanium alloys, this present work systematically investigates Ti60 (near-α)/TC18 (near-β) bimetal components manufactured by inertia radial friction welding. The focus is on understanding the joint interface behavior, heterogenous grain structure, microstructural evolution and resulting mechanical properties, with a particular emphasis on dynamic recrystallization, phase transformation and atomic diffusion of elements in the welded zone and thermos-mechanical affected zone. The results revealed that the significant influence of thermo-physical property mismatch between the dissimilar workpieces (Ti60-Ring and TC18-Core) on the microstructure and tensile strength of the joints. This mismatch could be effectively controlled by setting different flywheel kinetic energy (Ek) before welding. The tensile strength of the Ti60/TC18 joints manufactured with levels of Ek ranging from 174.74 kJ to 207.95 kJ, were observed to be governed by the combined effect of mechanical interlocking, grain boundary strengthening, precipitation strengthening and hetero-deformation induced strengthening. The formation of heterogeneous grain structure and intergrowth grains on the Ti60 alloy side, and the dislocation tangles in the “forked” α phase of the TC18 alloy side are identified as key factors in achieving optimized bonding strength for dissimilar Ti60/TC18 bimetallic inertia radial friction welding.