• • The WQ+400FC condition achieved a peak ultimate tensile strength (sigma_UTS) of 791.5 MPa with 16.7% elongation, delivering a strength-ductility product of 13.2 GPa*%, a 19% improvement over the WQ baseline (610 MPa, 18.2%). This demonstrates that a 29.8% strength increase can be attained with only a 1.5 percentage point ductility penalty, directly addressing the tradeoff that limits near-alpha titanium alloys in high-temperature structural applications.
• • The multi-stage heat treatment induced nano-martensite decomposition: alpha-prime/beta-prime phases transformed into homogeneously dispersed nano-scale alpha+beta precipitates during low-temperature FC, while equiaxed alpha grains coarsened via grain boundary migration. This microstructural refinement is critical for industrial scalability, as it enables property tuning without costly alloying additions or complex thermomechanical processing.
• • The 400FC sample exhibited the highest lattice strain inhomogeneity, with peak kernel average misorientation (KAM) of 1.5 degrees and grain orientation spread (GOS) of 0.96 degrees, which directly correlates with the enhanced sigma_UTS. These metrics provide a quantifiable quality-control parameter for heat treatment optimization in production environments.
• • BOR crystallographic reconstruction revealed variant selection during beta to alpha-prime transformation, yielding only four predominant alpha-prime variants instead of the twelve theoretically possible. This variant restriction, combined with higher Schmid factor values for non-basal slip systems after heat treatment, explains the retained ductility and offers a pathway for texture engineering in near-alpha titanium components.