Thermal stability, magnetic and mechanical properties of Fe–Dy–B–Nb bulk metallic glasses with high glass-forming ability

• BMGs with diameters up to 5.5 mm were synthesized in the FeDyBNb alloy system.
• The competitive formation of Fe23B6 and Dy2Fe14B phases leads to the best GFA.
• The FeDyBNb alloy system exhibits good soft-magnetic and mechanical properties.

The effects of Dy addition on the thermal stability, glass-forming ability (GFA), magnetic and mechanical properties of quaternary (Fe0.76−xDyxB0.24)96Nb4 (x = 0–0.07) bulk metallic glasses (BMGs) were investigated. Increasing Dy content from x = 0 to 0.05 extended the supercooled liquid region up to 112 K, allowing the fabrication by copper mold casting of BMGs rods with 5.5 mm in diameter. The high GFA was found to be related to the structure of primary crystalline phase. For the x = 0.05 alloy, the competitive formation process of the complex Fe23B6 and Dy2Fe14B phases enabled to obtain the largest GFA value. Moreover, the Fe–Dy–B–Nb BMGs exhibited good soft-magnetic properties, i.e., high saturation magnetization of 1.18–0.56 T and low coercive force of 1.9–21.6 A/m. In addition, the glassy alloy rods also showed high compressive fracture strengths of 4400–4150 MPa and high Vickers hardness of 1110–1090 kg/mm2.