Synthesis of CoCrMoCB bulk metallic glasses with high strength and good plasticity via regulating the metalloid content

•CoCrMoCB BMGs with critical diameter of 2–3.5 mm, fracture strength of 4.5–5 GPa and plasticity of 1–3% were fabricated.•The metalloid dependence of glass-forming ability was analyzed through the atomic packing density.•The influence of metalloid contents on strength and elasticity was investigated in terms of atomic bonding characters.

CoCrMoCB bulk metallic glasses (BMGs) with large glass-forming ability (GFA), large supercooled liquid region and excellent mechanical properties were obtained through regulating the contents of B and C. Fully glassy rod of Co50Cr15Mo14C10B11 with a diameter of 3.5 mm can be produced. The metalloid dependence of GFA in the present alloys was explained by the atomic packing density. Furthermore, the influence of metalloid on mechanical properties was explored. The high fracture strength of 4.5–5 GPa and outstanding plasticity of 1–3% can be observed. The contribution of C content to strength is larger than that of B content. In addition, the elastic moduli mainly depend on the B content, and the developed alloys possess high Poisson's ratio. In the view of atomic bonding characters, the reason for various effects of B and C contents on strength and elasticity is analyzed.