Enhanced strength–ductility balance in powder-metallurgy Ti-(2,6)Al–2Zr–1Mo–1V alloys via Al-content tailoring

Two powder metallurgy (PM) Ti-(2,6)Al-2Zr-1Mo-1V alloys with representative low and high Al contents were compared to examine the microstructural and tensile-property differences between low-Al and high-Al conditions. Both alloys were annealed in the α + β phase field to obtain bi-lamellar microstructures consisting of coarse primary α lamellae and β-transformed (β t ) regions containing acicular secondary α (αs) laths and retained β. In the 2 wt.% Al alloy, the microstructure contains 29 vol.% β t regions and 65 vol.% primary α lamellae, with the β t regions being harder than the α lamellae (average nanohardness: 4.57 vs. 4.19 GPa). As the Al content increased to 6 wt.%, the nanohardness of the α lamellae increased to 4.95 GPa, exceeding that of the β t regions (4.37 GPa), while the volume fraction of α lamellae increased to 77 vol.%. These microstructural changes with increasing Al content led to a significant increase in strength (yield strength: 811 to 1181 MPa; ultimate tensile strength: 917 to 1301 MPa). Notably, the marked increase in strength was accompanied by only a moderate reduction in ductility, with the elongation to fracture remaining at 17.4%. Detailed analysis suggests that the improved strength–ductility balance is associated with Al-induced strengthening of the α lamellae, a possible hetero-deformation-induced strengthening contribution associated with the increased hardness contrast between the α and β t regions, and the refined prior-β grain structure, which helps suppress premature crack formation. These findings show that increasing Al content from 2 wt.% to 6 wt.% can markedly enhance the strength of PM near-α titanium alloys while retaining good ductility, providing useful guidance for the comparative design of low-Al and high-Al PM near-α titanium alloys.