Effect of strain rate on the deformation mechanism of laser powder bed fusion (LPBF) Ti – 10V-2Fe-3Al alloy before and after solution treatment

Metastable β-titanium alloys can withstand both static and dynamic loads in applications, with mechanical properties closely related to the loading rate. This work investigated the differences in the deformation mechanism of Ti-1023 before and after solution treatment via LPBF, and the effect of the strain rate on its mechanical properties. The as-fabricated microstructure consists of (β+isothermal ω) phases, while the β-solutionized samples have (β+ω) phases. When the strain rate increased from 2×10-4s-1 to 4×103s-1, the compressive strength of the as-fabricated increased by 24%, the fracture strain increased by 150%. In contrast, the β-solutionized samples show a 5.8% decrease in compressive strength and a 40% reduction in fracture strain. The deformation mechanism of the as-fabricated samples is dominated by dislocation slip, while the β-solutionized samples primarily undergo stress-induced martensitic transformation (SIMT), driven by changes in [Mo]eq. In the as-fabricated samples, increasing strain rate raises dislocation density and motion speed, enhancing compressive strength. However, thermal softening above 2×10³ s⁻¹ causes a significant rise in fracture strain. In the β-solutionized samples, higher strain rates increase resistance to α"/β interface movement and elevate temperatures, both hindering the SIMT mechanism. While ωD transformation occurs at high strain rates, it cannot offset the weakening of SIMT.