Super-high strength of over 4000 MPa for Fe-based bulk glassy alloys in [(Fe 1− xCo x) 0.75B 0.2Si 0.05] 96Nb 4 system

Abstract

New Fe-based bulk glassy alloys with diameters up to 5 mm were formed in [(Fe 1− x Co x ) 0.75B 0.2Si 0.05] 96Nb 4 system by the copper mold casting method. The substitution of Co for Fe causes an increase in the glass-forming ability (GFA). As the Co content increases, the liquidus temperature ( T l) decreases, resulting in an increase of reduced glass transition temperature ( T g/ T l) from 0.566 to 0.587. The bulk glassy alloys exhibit super-high fracture strength of 3900–4250 MPa, Young's modulus ( E) of 190–210 GPa, elastic strain ( ε e) of 0.02, plastic strain ( ε p) of 0.0025 and Vickers hardness ( H v) of 1150–1220. The σ f/ E and H v/3 E of these glassy alloys are 0.02, respectively, in agreement with the previous data for a number of bulk glassy alloys. The agreement indicates that these Fe-based bulk glassy alloys have an elastic–plastic deformation mode. The syntheses of high-strength Fe-based bulk glassy alloys with super-high fracture strength of over 4000 MPa and high glass-forming ability are encouraging for future development of Fe-based bulk glassy alloys as structural materials.