Impact of Vanadium Presence on the Mechanical and Microstructural Characteristics of a Dilute Al–Sc–Zr–Si Alloy During Isothermal Aging

In this work, we studied precipitation tendency and resulting ambient and elevated temperature properties in low-V (Al-0.06Sc-0.06Zr-0.18Si-0.05V at.%), high-V (Al-0.06Sc-0.06Zr-0.18Si-0.10V at.%), and free-V (Al-0.06Sc-0.06Zr-0.18Si at.%) alloys subjected to isothermal aging at 300 °C and 400 °C. Scanning transmission electron microscopy revealed that V incorporated into Al3(Sc, Zr) nano-precipitates during aging, forming Al3(Sc, Zr, V) while retaining the spherical morphology and L12 order. Analysis showed that V delays precipitation kinetics by interacting with vacancies, requiring longer aging for peak strength. Both V alloys demonstrated increased peak microhardness around 50–100 MPa relative to the free-V alloy after extended aging. V also reduced precipitate coarsening rates during overaging. However, creep testing exhibited no improvements to threshold stress, indicating V did not expand the precipitate/matrix lattice mismatch needed for enhanced creep resistance. The threshold stress changed from 10.2 MPa in the free-V alloy to 10.4 MPa and 10.1 MPa in the low-V and high-V alloys, respectively. Instead, V localization in the interface of nano-precipitates with matrix contributed more stability. The precipitation strengthening mechanisms in all alloys were studied using established models for L12-reinforced systems. The results showed that coherency and ordering strengthening are the primary active mechanisms.