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

Abstract 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 VSS (V solid solution)-V3Si-V5SiB2 three-phase region of the respective phase diagram and differ in their primary solidification phase of either VSS, 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 VSS 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 VSS phase. Hence, the alloy containing primary VSS dendrites has the highest plastic strain compared to the V5SiB2 and V3Si primary crystallizing alloys. Investigations of the VSS phase on binary V–Si alloys reveal that silicon acts as solid solution strengthener, but ductility of the VSS 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.