Study of size effect on anisotropic deformation behavior of rolled α-Ti sheet

Abstract

Thin metal sheets are widely used in manufacturing miniaturized components through the micro forming process. However, the size effect on the plastic deformation behavior of thin metal sheets is significant, and the plastic anisotropy of rolled α-Ti sheets makes the micro forming process more complicated, which greatly limits the application of micro α-Ti components. A series of in-situ tensile tests were conducted using specimens with different sizes and orientations to investigate the size effect on the anisotropic deformation behavior of the α-Ti sheet. The microstructure and fracture morphology were observed, and the grain-scale deformation behavior of α-Ti was explored through full-field crystal plasticity simulation. The results indicate that the size effect on the tensile deformation behavior of α-Ti is anisotropic. The TD specimen has a greater size effect sensitivity and shows a more considerable fracture stain reduction with the specimen size decreasing. The twinning behavior in terms of types, morphology, and fractions is anisotropic and evolves with the specimen size. TD specimens show a more significant inhomogeneity of strain distribution than that of RD, and the difference increases with specimen size decreasing. More hard-oriented grain and massive local needle-like twins generated in small-sized TD specimens lead to severer strain localization. These findings provide a fundamental understanding of the anisotropic size effect in the micro forming process of α-Ti.