Nanolamellar and ultrafine equiaxed (α plus β) phase heterogeneously architected by nanotwins in a twinning-induced plasticity Ti-12Mo alloy

The role of deformation twins in precipitation behavior of alpha phases, crucial for enhancing the yield strength of twinning-induced plasticity (TWIP) titanium alloys is not yet fully elucidated. This study examines a metastable Ti-12Mo alloy, where high-density deformation twins were introduced via cold rolling. Following ageing treatments at 300-500 degrees C, we achieved a duplex microstructure comprising alpha and beta phases characterized by nanoscale lamellar and ultrafine equiaxed morphologies. The nanolamellar structure emerged from the nanotwinned regions, while the ultrafine equiaxed structure originated from the nanograined regions of the coldrolled sample. We found that alpha phase nucleation occurred concurrently in both nanotwin and nanograined regions, prior to recovery and recrystallization of the nanosized beta matrix. The growth of alpha and beta in the nanotwinned regions was restricted perpendicular to coherent twin boundaries, thereby forming nanoscale lamellar (alpha + beta) along the twin boundaries direction with an aspect ratio of 3.7. This innovative duplex microstructure, featuring both nanoscale lamellar and ultrafine equiaxed (alpha + beta) phases, imparts a remarkable yield strength of 1134 +/- 19 MPa to the Ti-12Mo alloy.