Elastic signatures of stability in Ir–Ni–Ta bulk metallic glasses

• Superior elastic properties of Ir-Ni-Ta bulk metallic glasses are experimentally obtained by in-situ ultrasonic interferometry. • Elastic parameters probe the structure and thermal stability of Ir-Ni-Ta bulk metallic glasses under pressure. • Higher Ir content of Ir-Ni-Ta bulk metallic glasses exhibit superior elastic performance attributed to its stiffer and more compact atomic structure. The advancement of bulk metallic glasses (BMGs) for extreme-environment applications is hindered by limited understanding of their elastic behavior and structural stability under high pressure. This study presents a comprehensive study of the high-pressure elastic properties of Ir–Ni–Ta BMGs using in-situ ultrasonic interferometry. Two representative compositions, Ir 29 Ni 29 Ta 42 and Ir 33 Ni 28 Ta 39 , exhibit pronounced elastic stiffening and robust structural integrity under compression, with zero-pressure bulk moduli of 213.7 and 245.0 GPa, shear moduli of 67.6 and 71.3 GPa, and Vickers hardness values of 10.1 and 10.4 GPa, respectively. Remarkable ductility is confirmed by high Pugh’s (3.16 and 3.44) and Poisson’s (0.357 and 0.367) ratios, indicating densely packed, cluster-dominated amorphous networks. Superior elastic performance in Ir 33 Ni 28 Ta 39 results from higher Ir content, which enhances 5d electron-driven covalent bonding and reduces molar volume (9.12 vs. 9.52 cm 3 /mol), yielding a stiffer structure. This difference in atomic packing manifests in distinct pressure derivatives of the bulk modulus ( B′ = 3.13 vs. 4.63), highlighting composition-dependent compressional responses. Furthermore, Debye temperature analysis predicts pressure-induced elevation of the glass transition temperature, confirming enhanced thermal stability. These findings establish direct correlations between atomic-scale bonding, elasticity, and thermal robustness in BMGs, guiding the rational design of amorphous alloys for extreme conditions.