Ultrastrong behaviors of a non-equiatomic Ti-Zr-Ni-Cu-Be high entropy metallic glass with ultrahigh glass forming ability

We studied the thermodynamics and kinetics of a non-equiatomic Ti _32.8Zr _30.2Ni _5.3Cu ₉Be _22.7 high entropy metallic glass (HEMG, ΔS_config.∼1.44R ) with a critical size for glass formation over 50 mm. The characteristic transition temperature, enthalpy of transition and specific heat capacity along with the relaxation time at different heating rate were determined using differential scanning calorimeter (DSC) measurements. It reveals that the present HEMG supercooled liquid shows the lowest thermodynamic driving force against the nucleation and growth of crystalline phases with comparing to other typical MG formers. Meanwhile, it exhibits the ultrastrong behavior near glass transition in terms of the Angell`s fragility concept. The alloy has a fragility index of D* = 45.2, higher than all the typical MG formers reported so far. Both thermodynamic and kinetic factors are responsible for the ultrahigh glass-forming ability of the HEMG alloys.