Yield surface and texture evolution in Ti-Cu Bimetal: Effects of tension and Tension-Cyclic torsion Pre-Deformation

Investigating of the material properties and physical mechanisms responsible for plastic deformation caused by complex loading is crucial for bimetallic structures. These materials are a type of functionally graded multi-material structures designed to combine diverse material properties within the same framework while optimizing manufacturing costs. In the present work, the initial yield surface and its subsequent evolution were determined for a Ti-Cu bimetal based on the definition of yield stress for 0.01% plastic offset strain. The subsequent yield surfaces were determined after introducing monotonic axial tension and axial tension-cyclic torsion pre-deformation up to 1% permanent axial strain. It was found, that the determined initial yield surface was close to the Huber-von Mises-Hencky isotropic yield locus. Furthermore, subsequent yield surfaces were determined to assess a hardening/softening effect in the loading direction applied. Interestingly, only the monotonic tension caused a significant enhancement of the tensile yield strength as the monotonic tension associated with cyclic torsion caused its reduction. On the other hand, the sizes of subsequent yield surfaces reflecting pre-deformation were reduced in the axial compression direction. Finally, microstructural studies revealed, that only shear strain magnitude affects the yielding behaviour of bimetallic structure since more slip systems were activated when the higher strain magnitude was applied. Consequently, material recrystallization and subsequent softening in the radial direction (RD) occurred. The texture evolution is primarily interface-driven and deformation-mode dependent.