Short-range order and thermal stability in amorphous alloys

Amorphous alloys of the types Zrsub(1-x)Nisub(x), Zrsub(1-x)Cosub(x), Zrsub(1-x)Fesub(x) and Zrsub(1-x)Cusub(x) were prepared by melt-spinning and studied by means of differential scanning calorimetry and x-ray diffraction. The crystallisation temperatures (Tsub(x)) and the activation energies for crystallisation (ΔE) were determined. The former values were found to vary only slightly with concentration while the latter show a marked concentration dependence, which is particularly pronounced in Zrsub(1-x)Nisub(x). It is shown that the predictions of the hole model are only slightly affected by the occurrence of CSRO, owing to a gross cancellation of the effect of a decreasing hole formation enthalpy and decreasing configurational entropy. The relatively strong temperature dependence of the configurational entropy expected for alloy compositions with strong CSRO leads to an increase in the experimental values of the apparent activation energies. From the concentration dependence of the experimental activation energies indications can be obtained about the concentration dependence of CSRO. (author)