Enhancing high-temperature strength in Al-Si alloys: The critical role of vanadium

Al-Si alloys are widely utilized in casting applications across various industries due to their favorable properties. This study addresses the imperative for improving the high-temperature strength of these alloys to expand their applicability. The stability of the microstructure of such alloys at elevated temperatures is closely associated with the diffusivity of their constituent elements. We explored the role of vanadium (V), which is known for its low diffusivity within the aluminum matrix, in enhancing the high-temperature strength of the Al-7Si alloy. The research evaluated mechanical properties, thermal stability, and fractographic characteristics of alloys. Microstructural analysis was conducted using optical microscopy (OM), scanning electron microscopy (SEM), transmission electron microscopy (TEM), and electron backscatter diffraction (EBSD), with a focus on identifying the strengthening mechanisms. Our results demonstrate that the incorporation of 0.5 wt% V significantly enhances the mechanical properties of alloys at both ambient and elevated temperatures. This improvement is primarily due to the formation of Al10V intermetallic particles, which hinder dislocation movement and increase dislocation density during deformation. Notably, the presence of twinning within Al10V contributes to a more uniform stress distribution, and it alleviates the typically detrimental effects on ductility observed with conventional brittle intermetallics. The joint addition of 0.2 wt% Ti and 0.5 wt% V further intensifies these benefits by increasing the number density of Al10V intermetallic particles. Our study highlights the considerable promise of V in improving the performance of aluminum alloys for high-temperature applications.