Micromechanical mechanisms of damage initiation and arrest in roll-compacted HDH-Ti green sheets

Continuous powder rolling of cost-effective hydride-dehydride titanium (HDH-Ti) offers a highly efficient and economical route for titanium sheet fabrication. Nevertheless, the severe morphological irregularity of HDH-Ti particles triggers intricate discontinuous-medium mechanics, inevitably inducing macro-defects: manifesting as structural porosity, edge cracking and lamellar tearing that critically undermine green sheet densification and structural integrity. To unravel the underlying micromechanical mechanisms, we establish a high-fidelity Discrete Element Method (DEM) framework that explicitly incorporates the angularity, aspect ratio, and granulometric distribution of HDH-Ti powders to elucidate granular kinematics and defect formation mechanisms during the roll-compaction process. Mechanistic analysis reveals that structural pores initiate within stress-shielded zones stabilized by strong force chains. Furthermore, edge cracking originates from weakened interfacial cohesion, driven by fine particle segregation and kinematic mismatch; whereas lamellar tearing is governed by anisotropic elastic recovery resulting from the preferential alignment of high-aspect-ratio particles. Guided by these fundamental insights, DEM simulations predict that a synergistic blending of ellipsoidal and irregular powders, coupled with a spatially tailored particle-size coordination strategy at the sheet edges, effectively suppresses all three failure modes. This work establishes a theoretically robust, mechanism-driven protocol for manufacturing sound, defect-free HDH-Ti green sheets.