Fe–B–Si–Zr soft magnetic bulk glassy alloys

• Fe–B–Si–Zr metallic glasses are designed with a cluster-plus-glue-atom model.
• Bulk glassy rods with diameters 1.5–2.5 mm are reached at the model compositions.
• These glassy alloys show wide supercooled liquid regions exceeding 30 K.
• These glassy alloys exhibit fracture strengths of 3800–3900 MPa.
• These glassy alloys exhibit high Ms (1.26–1.48 T) and low Hc (1.6–6.7 A/m).

The present work is devoted to fabrication of Fe–B–Si–Zr multi-component bulk glassy alloys with good mechanical and soft magnetic properties. Glass formation in Fe–B system is first considered with an empirical cluster-plus-glue-atom model. A basic composition formula [B–B2Fe8]Fe is proposed as the framework for multi-component alloy design. Considering the structural stability of the model glass, Si and Zr are introduced to the [B–B2Fe8] cluster to replace the center B and shell Fe atoms, from which a series of Fe–B–Si–Zr alloys with composition formulas [Si–B2Fe8−xZrx]Fe (x = 0–0.6) are derived. Copper mold casting experiment shows that bulk glassy alloys are formed within the Zr content range of x = 0.2–0.6, and the largest glass-forming ability appears at [Si–B2Fe7.6Zr0.4]Fe with a critical size of 2.5 mm. The bulk glassy alloys exhibit high fracture strength as large as 3850 MPa. Magnetic property measurement indicates that these alloys exhibit good magnetic softness with high saturation magnetization (1.26–1.48 T) and low coercive force (1.6–6.7 A/m). The alloying effects of Si and Zr on bulk glass formation, thermal glass stability and magnetic softness are discussed with the empirical model.