The kinetics of glass transition and the fragility of Zr₅₅Cu₃₀Al₁₀Ni₅ and (Zr₅₅Cu₃₀Al₁₀Ni₅)₉₈Nb₂ metallic glasses were investigated by the calorimetric measurements. The Nb minor addition narrows the width of glass transition, accelerates the relaxation process during glass transition, and decreases the energy barrier of glass transition. In addition, the fragility was evaluated in terms of the kinetic fragility index. While both alloys can be classified as intermediate glass formers, the Nb minor addition remarkably decreases the fragility and a stronger glass is achieved by the microalloying process. The lower fragility in the Nb-containing alloy is accompanied by higher degree of short-range ordering inferred from structural characterizations, formation of nanoscale chemical heterogeneities evidenced from the energy-dispersive X-ray spectroscopy (EDS) results, and deteriorated plasticity evaluated from the bending …