COMBINED MEASUREMENTS OF MODULUS AND LENGTH AND THEIR CORRELATION FOR DIFFERENT AMORPHOUS-ALLOYS

Combined measurements of length and modulus change on the same specimen of Ni78Si8B14, Cu64Ti36 and Co66Fe4(MoSiB)30 are presented. These properties are sensitive to different aspects of structural changes during relaxation in the amorphous state. The change of length is mainly sensitive to the topological long range relaxation. The change of the eigenfrequency is mainly sensitive to atomic rearrangements changing the chemical short range order. The results of the correlation between the effect of relaxation of frequency versus that of length can be described as follows: The observed structural relaxation in the amorphous states of each material can be divided up into two regimes. The first regime (I) with a prevailing change of eigenfrequency is attributed to short range rearrangements of the chemically different atomic species in the material; the second regime (II) with a larger amount of length change is interpreted as a long range topological relaxation with enhanced loss of "free volume". This interpretation is supported by a comparison of the diffusion coefficients at the characteristic transition temperature TC between the regimes I and II. It shows that the average diffusion path lengths of the possible diffusors below the characteristic temperature are in the order of 2 to 5 next neighbour distances, i.e. diffusion is only possible in a short range changing the species of neighbouring atoms. Above TC, the average diffusion path lengths are in the order of 5 to 50 next neighbour distances suggesting long range relaxation rearrangements by a diffusion process preferentially connected with the annihilation of free volume. © 1995.