Achieving Strength–Ductility Synergy in a Near‐α Powder Metallurgy Titanium Alloy via Deformation‐Induced Nanoscale β Precipitation

ABSTRACT

Powder metallurgy (PM) near‐α Ti alloys are often constrained by a pronounced strength–ductility trade‐off, due to the coarse lamellar microstructure formed during the sintering process. To address this issue, a thermomechanical route combining cyclic hot rolling with short‐time solution treatment was developed to improve the mechanical properties of a PM Ti‐6Al‐3Nb‐2Zr‐1Mo (Ti6321) alloy through multiscale microstructural regulation. The treatment refined the final α microstructure through early‐stage deformation and dissolution of residual α, deformation‐induced subdivision/recrystallization of the high‐temperature β matrix, and refined β→α transformation during cooling. For the thermomechanical samples subjected to 80% hot‐rolling reduction, strain‐induced anomalous segregation of β‐stabilizing elements (Nb and Mo) reduces the driving force for phase transformation. Consequently, highly dispersed intragranular nano‐β precipitates and transformed β structure (β _t ) regions are formed. This microstructure enables a satisfactory strength–ductility balance in the thermomechanical PM Ti alloy, achieving a yield strength of 1041.27 MPa and an elongation of 9.76%. This is attributed to a complex interplay: profound strengthening effects driven by intragranular nanoprecipitation, coupled with the coordinated activation of multiple deformation mechanisms. The α/β phase boundaries effectively mediated dislocation slip. In addition, the strengthening effect is enhanced by a transition in the deformation mode of nano‐β precipitates from a pinning mechanism to a shearing mechanism. Moreover, in the β _t regions, solute enrichment reduces the stacking fault energy, thereby activating pyramidal <c + a> slip and promoting three‐dimensional plastic deformation. This study provides a multiscale microstructural design strategy for developing high‐performance PM near‐α titanium alloys.