Unraveling the co-evolution of microstructure and damage in α-titanium

Abstract

Understanding damage and fracture mechanisms governed by microstructure evolution is fundamental to advancing high-performance metallic materials development and precision manufacturing optimization. However, simultaneous observation of internal damage and crystalline microstructure during deformation has remained challenging, hindering the direct exploration of their synergetic evolution and correlation. We have addressed this gap by innovatively proposing a correlative microscopy approach combining high-resolution in-situ synchrotron radiation X-ray computed tomography with in-damage-position electron backscattered diffraction characterization and applied it to investigate grain size-dependent damage mechanisms in α-titanium sheets. Defect development of α-titanium sheets is evidenced to transform from penny-shaped cracks propagation into spherical voids nucleation, growth, and coalescence as the grain size decreases. For the first time, the spheronization of microvoids is revealed to be triggered by twinning-induced dynamic recrystallization as a collaborative consequence of high-density dislocation and twinning structures. In addition, based on the resulting interpretation of microstructure-sensitive damage mechanisms, cryogenic pre-deformation is proposed to achieve recrystallization activation and manipulate fracture behavior by regulating the twinning structures, thereby preventing premature failure and enhanced ductility. Ultimately, the benefit of the cryogenic pre-deformation process is validated with microchannel stamping, providing novel guides for the forming performance improvement of α-titanium sheets in microforming.