Room temperature plastic deformability in V-rich V–Si–B alloys

In the present study compressive strength data and room temperature (RT) deformability of three V-rich V–Si–B alloys are reported. All alloys were taken from the V_SS (V solid solution)-V₃Si-V₅SiB₂ three-phase region of the respective phase diagram and differ in their primary solidification phase of either V_SS, V₃Si or V₅SiB₂. The RT yield stresses were determined by the 0.2% offset method and the plastic strain was obtained by subtracting the combined compliance of the testing machine and the specimen from the individually measured load-displacement curves. The microstructures in the as-cast and deformed state were analyzed using SEM, EBSD and TEM. Dislocation activity was only observed in the V_SS phase while the intermetallic phases were dislocation-free. Thus, the RT plasticity in V-rich V–Si–B alloys is mainly governed by the volume fraction of the V_SS phase. Hence, the alloy containing primary V_SS dendrites has the highest plastic strain compared to the V₅SiB₂ and V₃Si primary crystallizing alloys. Investigations of the V_SS phase on binary V–Si alloys reveal that silicon acts as solid solution strengthener, but ductility of the V_SS phase is retained throughout the solubility range. The present results are quite astonishing since Mo–Si–B alloys containing similar amounts of Si and B are known to be fairly brittle at RT.