Probing the decoupling degree between α and β relaxations in metallic glasses through differential scanning calorimetry

•Dynamic transition from β to α relaxation is observed with increasing Ta.•The origin of the transition resides in the different growth rate of MROs.•Two parameters were decided via DSC to assess different behaviors of β relaxation.•The increase in Eg/Eonset results in the more pronounced β relaxation peak.•The Tonset/Ta,C decrease leads to stronger decoupling between α and β relaxations. The β relaxation is an intrinsic and crucial feature of metallic glasses (MGs). An interesting puzzle is that why the β relaxation exhibits different behaviors in different MGs. Here, a comprehensive studying strategy through differential scanning calorimetry is designed to evaluate the different β relaxations in La-based MGs. This method is based on the onset temperature and activation energy of sub-Tg enthalpy relaxation (Tonset and Eonset), the activation energy of glass transition (Eg) and the critical annealing temperature (Ta,C). Ta,C is the annealing temperature where the dynamic transition from β to α relaxation is observed. The origin of this transition resides in the different growth rate of medium range orders. The pronounced β relaxations are always associated with MGs exhibiting both larger Eg/Eonset and smaller Tonset/Ta,C. This finding provides an alternative avenue to evaluate the decoupling degree between α and β relaxations in MGs.