(NbMoTiVSi

0.2

)

100-x

B

x

refractory high entropy alloy ingots with different addition of boron were prepared

and the phase constitution

microstructure and mechanical properties of the alloy were investigated. The results indicate that phase constitution of alloys remains stable after boron addition

which consists of BCC and silicide phase

and eutectic structure composed of the both phases are formed on the grain boundaries. The dendrite structure and eutectic structure of alloys are refined with boron content increasing

and the morphologies are converted from dendrite structure to near equiaxed grains. The yield strength of alloys is increased from 1 766 MPa to 2 076 MPa

the ultimate strength is increased from 2 091 MPa to 2 270 MPa

and the fracture strain is reduced from 16.47% to 13.33%. The strength of alloy is synergistically improved by grain refinement strengthening and solid solution strengthening

while plasticity improvement induced by grain refinement effect is unable to offset the plasticity decrease caused by the solid solution strengthening effect

therefore the plasticity is decreased with increase of boron.