Fragility and thermal stability of Pt- and Pd-based bulk glass forming liquids and their correlation with deformability

The fragility parameter m of (Pt or Pd)–(Ni, Cu)–P bulk metallic glasses (BMGs) was characterized and compared to other systems. The results indicate that the Pt 65Ni 15P 25 alloy is the most fragile and thermally stable at the supercooled liquid state, thus is the most workable among the presently developed BMGs. To express the degree of workability, a deformability d ∗ = log [ η ( T g ∗ ) / η ( T x ) ] is introduced then correlated with m and the reduced thermal stability Δ T rx ∗ = ( T x - T g ∗ ) / T g ∗ . A master curve in term of η ( T g ∗ ) / η ( T ) and m · [ ( T - T g ∗ ) / T g ∗ ] has been established for various BMGs, d ∗ thus can be uniquely related to m · Δ T rx ∗ .