Simultaneously increasing strength and plasticity of lamellar TA15 alloy via multi-step hot-rolling process

Dual-phase titanium alloys are the most used Ti alloys in industries due to their extraordinary comprehensive mechanical properties. However, the enhancement of strength always sacrifices their ductility. In the present study, a dual-phase TA15 alloy with both high strength and ductility was developed through a multi-step hot rolling process. The tensile strength increased from 827 MPa to 1222 MPa with an increase of 47.76 %, while ductility increased by 18.84 %. The microstructures prior to and subsequent to the hot rolling were systematically characterized. The crystal orientations of the α phaseα-Ti grains rotated towards the favorable orientations, forming layered heterostructure. The proportion of low angle grain boundaries increased significantly from 2.1 % to 78.3 %. Additionally, the density of stored geometrically necessary dislocations raised dramatically from 2.0 × 10¹⁴ m⁻² to 5.26 × 10¹⁴ m⁻². During the multi-step hot deformation process, nano-scaled secondary α-Ti lamellae with an average thickness of 14 nm formed with a fully coherent interface {110}_BCC//{0002}_HCP. The formed favorable orientations and low-angle grain boundaries enlarged the dislocation activity and improve the ductility. The enhancement of strengthen was primarily contributed to the increased dislocation density and the hetero-phase boundaries.