Investigation on the Interaction Mechanism between {11-22} and {11-24} Twins in Cryogenically Rolled Commercially Pure Titanium

The interaction behavior of {11-22} and {11-24} compression twins plays a critical role in governing the microstructural evolution and plastic deformation behavior of commercially pure titanium under cryogenic conditions. The interaction mechanism and variant selection criteria for secondary twinning were systematically analyzed using cryogenic rolling experiments in liquid nitrogen and electron backscatter diffraction (EBSD) characterization, along with geometric compatibility factor (m') and normalized Schmid factor (NSF) analyses. The findings demonstrated four distinct interactions between {11-22} and {11-24} twins, where most interactions caused growth stagnation and stress concentration, but the Type II interaction, an incoming {11-22} twin impinging on a pre-existing {11-24} twin, anomalously induced the formation of interfacial {10-12} secondary twins. Statistical analysis demonstrated high geometric compatibility (m' > 0.83) and a high macroscopic driving force for the activated secondary variants, with 98.8% of the variants showing an NSF exceeding 0.9. This unique secondary twinning mechanism enables incoming twins to penetrate boundary barriers, sustaining the growth of the twinning network and playing a crucial role in accommodating plastic deformation in titanium at cryogenic temperatures.