Effect of Boron Alloying on the Structure and Mechanical Properties of Multicomponent Fe–Co–Ni–Cr–V Alloys

The work investigated the effect of alloying with boron of alloys of the system (Fe0.25Co0.25Ni0.25Cr0.125V0.125)100 – xBx (at %), where x = 0–9 on microstructure and mechanical properties during crystallization with cooling rates of 103–104 K/s. It has been established that an increase in the boron content leads to an increase in the volume fraction of the eutectic in the structure of the alloys. The structure of the alloys with increasing boron content changes from a single-phase structure of a multicomponent solid solution with an fcc lattice to a typical hypoeutectic structure – dendrites of a solid solution surrounded by a eutectic consisting of a solid solution and boride Me3B2. Using X-ray diffraction and micro-X-ray spectral analysis methods, it was established that an increase in the boron content leads to a depletion of the solid solution in vanadium and chromium, which is due to their high content in the boride and an increase in its volume fraction in the structure. Increasing the boron content from 0 to 9 at % leads to an increase in the yield strength of alloys from 236 to 500 MPa, tensile strength from 514 to 798 MPa and a decrease in relative elongation from 28.1 to 3.2%. It has been shown that alloys with a boron content of up to 5 at % can be subjected to cold deformation, which leads to a significant increase in the yield strength to values exceeding 1 GPa.