Non-exponentiality of structural relaxations in glass forming metallic liquids

The non-exponentiality of structural relaxations in glass forming metallic liquids is studied with an emphasis of a comparison of modulus relaxation and enthalpy relaxation measurements. The non-exponential (stretching or Kohlrausch) parameter βKWW determined from the modulus measurements of metallic liquids does not exhibit appreciable difference, and a definite fragility dependence is lacking. Extensive analyses of modulus relaxation data of molecular (mechanical) and ionic liquids (electrical) repeat the observation in metallic liquids. By contrast, the enthalpy relaxation measurements of metallic glasses gave distinct βKWW values, and the use of the enthalpy relaxation dispersion results largely restores Böhmer's correlation. A discussion is presented with regards to enthalpy, compliance and modulus relaxations.