The stress relaxation dynamics of a ${\mathrm{La}}_{60}{\mathrm{Ni}}_{15}{\mathrm{Al}}_{25}$ metallic glass were studied in ribbon and bulk samples. In both tensile and single cantilever testing modes, it is observed that the stress decay of deep glass is mediated by the β relaxation, which contributes about 5% to the total stress. The characteristic time of stress relaxation near the glass transition coincides with that of the α relaxation, indicating that the two-step stress decay may correspond directly to the two dynamic relaxations. A possible atomic mechanism involving both relaxation and deformation is proposed based on the evolution of shear transition zone, which enables reconstruction of the two-step deformation theoretically. The present experimental and theoretical protocol further provides a strategy to detect the β relaxation associated phenomena at room temperature and even lower, circumventing interference from physical aging or the α relaxation. These findings clarify the elusive roles of relaxation modes in the nonelastic deformation of amorphous matters and reveal the interrelationships between them.

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• Mechanical deformation
• Stress
• Metallic glasses