Glass-forming ability, fragility parameter, and mechanical properties of Co–Ir–Ta–B amorphous alloys

Abstract The effect of partial substitution of Co by Ir in Co 57− x Ir x Ta 8 B 35 (at.%, x = 0, 5, 10, and 15) alloys on glass-forming ability (GFA), fragility parameter m , and mechanical properties was investigated. It was found that the glass-forming ability reflected by critical diameter for glass formation is in good agreement with the width of supercooled region (Δ T x ). The Co 47 Ir 10 Ta 8 B 35 BMG exhibits the best GFA yielding the formation of an amorphous rod with a diameter of 5 mm, along with the largest Δ T x value of 64 K. The Ir-bearing Co 47 Ir 10 Ta 8 B 35 BMG presents a lower fragility parameter m than Co 57 Ta 8 B 35 BMG, which indicates better thermal stability and GFA. In addition, the Co 47 Ir 10 Ta 8 B 35 BMG shows super-high yield strength of ∼5200 MPa and ultimate compressive strength of ∼5600 MPa as well as significant plasticity of ∼1.2%. The combination of good GFA, large Δ T x and excellent mechanical properties for the new Co–Ir–Ta–B BMG is significant for scientific research and industrial application.