Improvement of the strength of ternary eutectic V-Si-B alloys at ambient and high temperatures due to Cr additions

In the present study high-temperature compression tests on a chromium-alloyed ternary eutectic V-9Si-6.5B are reported. The ternary eutectic composition is located within the V SS (V solid-solution)-V 3 Si-V 5 SiB 2 three-phase region of the respective V-rich corner of the phase diagram. The high-temperature compressive yield stresses were determined by the 0.5 % 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 heat-treatment state (1400 °C / 100 hrs) were analyzed using SEM, EBSD and TEM observations. The effect of Cr on the ternary eutectic formation was studied. After compression testing, dislocation activities were observed in the V SS and V 3 Si phases, while the ternary intermetallic phases were dislocation-free. The high-temperature plasticity in the Cr-added ternary eutectic alloys V-9Si-6.5B+xCr is mainly governed the V SS phase which forms the major phase of the eutectic. Thus, Cr additions are found to contribute to solid-solution strengthening in the ternary eutectic alloys while strongly influencing the deformability by decreasing the temperature at which brittle failure occurs in the present compression experiments. • Cr additions stabilize the eutectic phases V SS , V 3 Si and V 5 SiB 2 • Cr acts as effective solid-solution strengthener. • Cr leads to embrittlement, resulting in brittle failure during compression test at temperatures < 600 °C. • Annealing at 1400 °C does not affect the solid-state transformation from V 5 SiB 2 into V 8 SiB 4 at Cr additions < 30 at%. • Deformation occurs in the V SS phase but dislocations were found in V 3 Si at test temperatures of 800 °C.